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Radiative corrections to superallowed beta decays at $\mathcal O(α^2 Z)$
Authors:
Òscar L. Crosas,
Emanuele Mereghetti
Abstract:
We compute $\mathcal O(α^2 Z)$ radiative corrections to superallowed $β$ decays with a heavy-particle effective field theory that systematically describes the interactions of low-energy ultrasoft photons with nuclei. We calculate two-loop virtual and one-loop real-virtual amplitudes by reducing the Feynman integrals to a set of master integrals, which we solve analytically using a variety of techn…
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We compute $\mathcal O(α^2 Z)$ radiative corrections to superallowed $β$ decays with a heavy-particle effective field theory that systematically describes the interactions of low-energy ultrasoft photons with nuclei. We calculate two-loop virtual and one-loop real-virtual amplitudes by reducing the Feynman integrals to a set of master integrals, which we solve analytically using a variety of techniques. These techniques can be applied to other phenomenologically interesting observables. The ultrasoft corrections can then be combined with contributions arising from the exchange of potential photons to obtain the complete $\mathcal O(α^2 Z)$ correction to the decay rate, with resummation of large logarithms of the electron energy times the nuclear radius. We find that $\mathcal O(α^2 Z)$ ultrasoft loops induce a relative correction to the decay rate that ranges from $0.7 \cdot 10^{-3}$ in the decay of $^{10}$C to $3.6 \cdot 10^{-3}$ in the decay of $^{54}$Co, and will thus impact the extraction of $V_{ud}$ at the permille level. We show that the inclusion of these corrections reduces the residual renormalization scale dependence of the decay rate to a negligible level, making missing ultrasoft perturbative corrections a subdominant source of theoretical error.
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Submitted 7 November, 2025;
originally announced November 2025.
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Towards the determination of CP-odd pion-nucleon couplings
Authors:
Shohini Bhattacharya,
Kaori Fuyuto,
Emanuele Mereghetti,
Thomas R. Richardson
Abstract:
The nucleon matrix elements (NMEs) associated with quark chromo-magnetic dipole moments (cMDMs) play a crucial role in determining the CP-odd pion-nucleon couplings induced by quark chromo-electric dipole moments. In recent years, it has been argued that the NMEs of cMDMs can be related to the third moment of the nucleon's higher-twist (specifically, twist-three) parton distribution function (PDF)…
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The nucleon matrix elements (NMEs) associated with quark chromo-magnetic dipole moments (cMDMs) play a crucial role in determining the CP-odd pion-nucleon couplings induced by quark chromo-electric dipole moments. In recent years, it has been argued that the NMEs of cMDMs can be related to the third moment of the nucleon's higher-twist (specifically, twist-three) parton distribution function (PDF) $e(x)$, which can, in principle, be measured through dihadron production in semi-inclusive deep inelastic scattering processes. By applying the spin-flavor expansion to the cMDM operators in the large-$N_c$ limit, where $N_c$ is the number of quark colors, we show that the NMEs receive contributions not only from the twist-three PDF $e(x)$ but also from an additional, previously neglected nucleon form factor. Incorporating constraints from the spin-flavor expansion, recent experimental data on $e(x)$, as well as model calculations of $e(x)$, we estimate the NMEs of the cMDM operators. Our analysis indicates that the NMEs are dominated by the nucleon form factors, and the cMDM contributions to pion-nucleon couplings can be comparable to those from the quark sigma terms.
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Submitted 1 April, 2025;
originally announced April 2025.
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Signs of Non-Monotonic Finite-Volume Corrections to $g_A$
Authors:
Zack B. Hall,
Dimitra A. Pefkou,
Aaron S. Meyer,
Thomas R. Richardson,
Raúl A. Briceño,
M. A. Clark,
Martin Hoferichter,
Emanuele Mereghetti,
Henry Monge-Camacho,
Colin Morningstar,
Amy Nicholson,
Pavlos Vranas,
André Walker-Loud
Abstract:
We study finite-volume (FV) corrections to determinations of $g_A$ via lattice quantum chromodynamics (QCD) using analytic results and numerical analysis. We observe that $SU(2)$ Heavy Baryon Chiral Perturbation Theory does not provide an unambiguous prediction for the sign of the FV correction, which is not surprising when one also considers large-$N_c$ constraints on the axial couplings. We furt…
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We study finite-volume (FV) corrections to determinations of $g_A$ via lattice quantum chromodynamics (QCD) using analytic results and numerical analysis. We observe that $SU(2)$ Heavy Baryon Chiral Perturbation Theory does not provide an unambiguous prediction for the sign of the FV correction, which is not surprising when one also considers large-$N_c$ constraints on the axial couplings. We further show that non-monotonic FV corrections are naturally allowed when one considers either including explicit $Δ$-resonance degrees of freedom or one works to higher orders in the chiral expansion. We investigate the potential impact of these FV corrections with a precision study of $g_A$ using models of FV corrections that are monotonic and non-monotonic. Using lattice QCD data that is approximately at the 1% level of precision, we do not see significant evidence of non-monotonic corrections. Looking forward to the next phase of lattice QCD calculations, we estimate that calculations that are between the 0.1%-1%-level of precision may be sensitive to these FV artifacts. Finally, we present an update of the CalLat prediction of $g_A$ in the isospin limit with sub-percent precision, $g_A^{\rm QCD} = 1.2674(96)$.
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Submitted 12 March, 2025;
originally announced March 2025.
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Gradient flow of the Weinberg operator
Authors:
Tanmoy Bhattacharya,
Shohini Bhattacharya,
Vincenzo Cirigliano,
Rajan Gupta,
Emanuele Mereghetti,
Sungwoo Park,
Jun-Sik Yoo,
Boram Yoon
Abstract:
We present preliminary results on the susceptibilities involving the CP-violating (CPV) Weinberg three-gluon operator and the topological $Θ$ term using the gradient flow scheme, and study their continuum and chiral extrapolations. These are used to provide an estimate of the $Θ$ induced by the Weinberg operator in theories with the Peccei-Quinn (PQ) mechanism. Combined with the calculations of th…
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We present preliminary results on the susceptibilities involving the CP-violating (CPV) Weinberg three-gluon operator and the topological $Θ$ term using the gradient flow scheme, and study their continuum and chiral extrapolations. These are used to provide an estimate of the $Θ$ induced by the Weinberg operator in theories with the Peccei-Quinn (PQ) mechanism. Combined with the calculations of the matrix elements (MEs) of quark-bilinears between nucleon states, such calculations will enable estimates of the electric dipole moments (EDMs) and CPV pion-nucleon couplings due to the Weinberg operator, thereby providing robust constraints on beyond the standard model (BSM) physics.
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Submitted 1 February, 2025;
originally announced February 2025.
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$2νββ$ Spectrum in Chiral Effective Field Theory
Authors:
Saad el Morabit,
Ryan Bouabid,
Vincenzo Cirigliano,
Jordy de Vries,
Lukáš Gráf,
Emanuele Mereghetti
Abstract:
We investigate two-neutrino double beta decay ($2νββ$) in chiral effective field theory. We find contributions from weak magnetism and double-weak pion-exchange at next-to-leading-order in the chiral power counting. We discuss the impact of the chiral corrections on the electron spectra and find that they should be included in analyses of $2νββ$ decay that aim to uncover new physics signatures in…
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We investigate two-neutrino double beta decay ($2νββ$) in chiral effective field theory. We find contributions from weak magnetism and double-weak pion-exchange at next-to-leading-order in the chiral power counting. We discuss the impact of the chiral corrections on the electron spectra and find that they should be included in analyses of $2νββ$ decay that aim to uncover new physics signatures in the electron spectrum. We illustrate this point by revisiting the effect of sterile neutrinos and non-standard charged interactions. We also find that the pion-exchange contributions involve nuclear matrix elements that are related to those appearing in neutrinoless double beta decay ($0νββ$). We investigate whether the $0νββ$ nuclear matrix elements can be obtained from detailed measurements of the energy spectrum of the outgoing electrons in $2νββ$ transitions.
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Submitted 18 December, 2024;
originally announced December 2024.
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Global analysis of $μ\to e$ interactions in the SMEFT
Authors:
Filippo Delzanno,
Kaori Fuyuto,
Sergi Gonzàlez-Solís,
Emanuele Mereghetti
Abstract:
We study current experimental bounds on charged lepton flavor violating (CLFV) $μ$-$e$ interactions in the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Assuming a generic flavor structure in the quark sector, we consider the contributions of CLFV operators to low-energy observables, including $μ\to eγ$ and $μ\to e$ conversion for quark-flavor conserving operato…
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We study current experimental bounds on charged lepton flavor violating (CLFV) $μ$-$e$ interactions in the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Assuming a generic flavor structure in the quark sector, we consider the contributions of CLFV operators to low-energy observables, including $μ\to eγ$ and $μ\to e$ conversion for quark-flavor conserving operators and CLFV meson decays for quark-flavor violating operators. At high energy, we consider limits on CLFV decays of the Higgs and Z bosons and of the top quark, and obtain bounds on operators with light quarks by recasting searches for production of $eμ$ pairs in $pp$ collisions at the Large Hadron Collider (LHC). We connect observables at low- and high-energy by taking into account renormalization group running and matching between CLFV operators. We also discuss the sensitivity of the future Electron-Ion Collider, where the prospective bounds are derived by imposing simple cuts on final state particles. We find that, in a single operator scenario, bounds on purely leptonic operators are dominated by $μ\rightarrow e γ$ and $μ\rightarrow e$ conversion. Semileptonic operators with down-type quarks are also dominantly constrained by low-energy observables, while LHC searches lead the bounds on up-type quark-flavor violating operators. Taking simplified multiple-coupling scenarios, we show that it is easy to evade the strongest low-energy bounds from spin-independent $μ\rightarrow e$ conversion, and that collider searches are competitive and complementary to constraints from spin-dependent $μ\rightarrow e$ conversion and other low-energy probes.
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Submitted 20 November, 2024;
originally announced November 2024.
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Effective field theory for radiative corrections to charged-current processes II: Axial-vector coupling
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Emanuele Mereghetti,
Oleksandr Tomalak
Abstract:
We discuss the hadronic structure-dependent radiative corrections to the axial-vector coupling that controls single-nucleon weak charged-current processes -- commonly denoted by $g_A$. We match the Standard Model at the GeV scale onto chiral perturbation theory at next-to-leading order in the one-nucleon sector, in the presence of electromagnetic and weak interactions. As a result, we provide a re…
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We discuss the hadronic structure-dependent radiative corrections to the axial-vector coupling that controls single-nucleon weak charged-current processes -- commonly denoted by $g_A$. We match the Standard Model at the GeV scale onto chiral perturbation theory at next-to-leading order in the one-nucleon sector, in the presence of electromagnetic and weak interactions. As a result, we provide a representation for the corrections to $g_A$ in terms of infrared finite convolutions of simple kernels with the single-nucleon matrix elements of time-ordered products of two and three quark bilinears (vector, axial-vector, and pseudoscalar). We discuss strategies to determine the required non-perturbative input from data, lattice-QCD (+QED), and possibly hadronic models. This work paves the way for a precise comparison of the values of the ratio $g_A/g_V$ extracted from experiment and from lattice-QCD, which constrain physics beyond the Standard Model.
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Submitted 19 March, 2025; v1 submitted 28 October, 2024;
originally announced October 2024.
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Radiative corrections to proton-proton fusion in pionless EFT
Authors:
Evan Combes,
Emanuele Mereghetti,
Lucas Platter
Abstract:
We study the leading radiative correction to proton-proton fusion using the pionless effective field theory framework at leading order. We derive the relevant matrix elements and evaluate them using the method of regions. We benchmark the accuracy of our approximations by carrying out numerical computations of the full expressions. We show that the first order radiative corrections due to the exch…
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We study the leading radiative correction to proton-proton fusion using the pionless effective field theory framework at leading order. We derive the relevant matrix elements and evaluate them using the method of regions. We benchmark the accuracy of our approximations by carrying out numerical computations of the full expressions. We show that the first order radiative corrections due to the exchange of a Coulomb photon between positron and proton-proton systems map onto the Sirlin function and the $\mathcal{O}(α)$ contribution from the Fermi function. We furthermore find that the nuclear structure dependent radiative correction omitted in the previous analysis by Kurylov {\it et al} gives an up to 0.2~\% correction to the pp fusion S-factor with its size ultimately depending on a two-nucleon counterterm that renormalizes the axial two-body current $L_{1A}$.
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Submitted 10 July, 2024;
originally announced July 2024.
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Radiative corrections to superallowed $β$ decays in effective field theory
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Stefano Gandolfi,
Martin Hoferichter,
Emanuele Mereghetti
Abstract:
The accuracy of $V_{ud}$ determinations from superallowed $β$ decays critically hinges on control over radiative corrections. Recently, substantial progress has been made on the single-nucleon, universal corrections, while nucleus-dependent effects, typically parameterized by a quantity $δ_\text{NS}$, are much less well constrained. Here, we lay out a program to evaluate this correction from effec…
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The accuracy of $V_{ud}$ determinations from superallowed $β$ decays critically hinges on control over radiative corrections. Recently, substantial progress has been made on the single-nucleon, universal corrections, while nucleus-dependent effects, typically parameterized by a quantity $δ_\text{NS}$, are much less well constrained. Here, we lay out a program to evaluate this correction from effective field theory (EFT), highlighting the dominant terms as predicted by the EFT power counting. Moreover, we compare the results to a dispersive representation of $δ_\text{NS}$ and show that the expected momentum scaling applies even in the case of low-lying intermediate states. Our EFT framework paves the way towards ab-initio calculations of $δ_\text{NS}$ and thereby addresses the dominant uncertainty in $V_{ud}$.
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Submitted 18 November, 2024; v1 submitted 28 May, 2024;
originally announced May 2024.
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Ab-initio electroweak corrections to superallowed $β$ decays and their impact on $V_{ud}$
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Stefano Gandolfi,
Martin Hoferichter,
Emanuele Mereghetti
Abstract:
Radiative corrections are essential for an accurate determination of $V_{ud}$ from superallowed $β$ decays. In view of recent progress in the single-nucleon sector, the uncertainty is dominated by the theoretical description of nucleus-dependent effects, limiting the precision that can currently be achieved for $V_{ud}$. In this work, we provide a detailed account of the electroweak corrections to…
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Radiative corrections are essential for an accurate determination of $V_{ud}$ from superallowed $β$ decays. In view of recent progress in the single-nucleon sector, the uncertainty is dominated by the theoretical description of nucleus-dependent effects, limiting the precision that can currently be achieved for $V_{ud}$. In this work, we provide a detailed account of the electroweak corrections to superallowed $β$ decays in effective field theory (EFT), including the power counting, potential and ultrasoft contributions, and factorization in the decay rate. We present a first numerical evaluation of the dominant corrections in light nuclei based on Quantum Monte Carlo methods, confirming the expectations from the EFT power counting. Finally, we discuss strategies how to extract from data the low-energy constants that parameterize short-distance contributions and whose values are not predicted by the EFT. Combined with advances in ab-initio nuclear-structure calculations, this EFT framework allows one to systematically address the dominant uncertainty in $V_{ud}$, as illustrated in detail for the $^{14}$O $\to$ $^{14}$N transition.
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Submitted 18 November, 2024; v1 submitted 28 May, 2024;
originally announced May 2024.
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Sterile neutrino dark matter within the $ν$SMEFT
Authors:
Kaori Fuyuto,
Jacky Kumar,
Emanuele Mereghetti,
Stefan Sandner,
Chen Sun
Abstract:
Sterile neutrinos with masses at the $\mathrm{keV}$ scale and mixing to the active neutrinos offer an elegant explanation of the observed dark matter (DM) density. However, the very same mixing inevitably leads to radiative photon emission and the non-observation of such peaked $X$-ray lines rules out this minimal sterile neutrino DM hypothesis. We show that in the context of the Standard Model ef…
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Sterile neutrinos with masses at the $\mathrm{keV}$ scale and mixing to the active neutrinos offer an elegant explanation of the observed dark matter (DM) density. However, the very same mixing inevitably leads to radiative photon emission and the non-observation of such peaked $X$-ray lines rules out this minimal sterile neutrino DM hypothesis. We show that in the context of the Standard Model effective field theory with sterile neutrinos ($ν$SMEFT), higher dimensional operators can produce sterile neutrino DM in a broad range of parameter space. In particular, $ν$SMEFT interactions can open the large mixing parameter space due to their destructive interference, through operator mixing or matching, in the $X$-ray emission. We also find that, even in the zero mixing limit, the DM density can always be explained by $ν$SMEFT operators. The testability of the studied $ν$SMEFT operators in searches for electric dipole moments, neutrinoless double beta decay, and pion decay measurements is discussed.
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Submitted 30 April, 2024;
originally announced May 2024.
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Electric Dipole Moments in 5+3 Flavor Weak Effective Theory
Authors:
Jacky Kumar,
Emanuele Mereghetti
Abstract:
A fully generic treatment of electric dipole moments (EDMs) is presented in the CP-violating and flavor-conserving weak effective field theory (WET) with five flavors of quarks and three flavors of leptons. We systematically analyze leading contributions to EDMs originating from QCD and QED renormalization group running between the electroweak scale and low energy scales of about 2 GeV. We include…
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A fully generic treatment of electric dipole moments (EDMs) is presented in the CP-violating and flavor-conserving weak effective field theory (WET) with five flavors of quarks and three flavors of leptons. We systematically analyze leading contributions to EDMs originating from QCD and QED renormalization group running between the electroweak scale and low energy scales of about 2 GeV. We include the full one-loop anomalous dimension and a subset of two-loop corrections, as well as threshold corrections at the bottom, charm and $τ$ masses. This allows us to derive master formulae in the space of generic WET for the neutron and proton EDMs, for EDMs of diamagnetic atoms, and the precession frequencies constrained in molecular EDM experiments, from which bounds on the electron EDM are extracted. In particular, our master formulae capture the contributions of WET CP-violating operators with heavy quark and lepton flavors. As an application, we study EDM constraints on the Yukawa couplings of the Higgs boson, in both the linear and non-linear realizations of electroweak symmetry breaking.
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Submitted 11 June, 2024; v1 submitted 30 March, 2024;
originally announced April 2024.
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Neutrinoless double beta decay rates in the presence of light sterile neutrinos
Authors:
W. Dekens,
J. de Vries,
D. Castillo,
J. Menéndez,
E. Mereghetti,
V. Plakkot,
P. Soriano,
G. Zhou
Abstract:
We investigate neutrinoless double-beta decay ($0νββ$) in minimal extensions of the Standard Model of particle physics where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We argue that the standard treatment of these scenarios, based on mass-dependent nuclear matrix elements, is missing important contributions to the $0νββ$ amplitude. First, new effects…
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We investigate neutrinoless double-beta decay ($0νββ$) in minimal extensions of the Standard Model of particle physics where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We argue that the standard treatment of these scenarios, based on mass-dependent nuclear matrix elements, is missing important contributions to the $0νββ$ amplitude. First, new effects arise from the exchange of neutrinos with very small (ultrasoft) momenta, for which we compute the associated nuclear matrix elements for the decays of ${}^{76}$Ge and ${}^{136}$Xe. These contributions can dominate the $0νββ$ rate in cases with light sterile neutrinos. The ultrasoft terms are also relevant in the more standard scenario of just three light Majorana neutrinos where they lead to a $10\%$ reduction of the total $0νββ$ amplitude. Secondly, we highlight the importance of short-range terms associated with medium-heavy sterile neutrinos and provide explicit formulae that can be used in phenomenological analyses. As examples we discuss impact of these new effects in several explicit scenarios, including a realistic $3+2$ model with two right-handed gauge-singlet neutrinos.
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Submitted 25 October, 2024; v1 submitted 12 February, 2024;
originally announced February 2024.
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Anomalies in global SMEFT analyses: a case study of first-row CKM unitarity
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Emanuele Mereghetti,
Tom Tong
Abstract:
Recent developments in the Standard Model analysis of semileptonic charged-current processes involving light quarks have revealed $\sim 3σ$ tensions in Cabibbo universality tests involving meson, neutron, and nuclear beta decays. In this paper, we explore beyond the Standard Model explanations of this so-called Cabibbo Angle Anomaly in the framework of the Standard Model Effective Field Theory (SM…
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Recent developments in the Standard Model analysis of semileptonic charged-current processes involving light quarks have revealed $\sim 3σ$ tensions in Cabibbo universality tests involving meson, neutron, and nuclear beta decays. In this paper, we explore beyond the Standard Model explanations of this so-called Cabibbo Angle Anomaly in the framework of the Standard Model Effective Field Theory (SMEFT), including not only low-energy charged current processes (`L'), but also electroweak precision observables (`EW') and Drell-Yan collider processes (`C') that probe the same underlying physics across a broad range of energy scales. The resulting `CLEW' framework not only allows one to test explanations of the Cabibbo Angle Anomaly, but is set up to provide near model-independent analyses with minimal assumptions on the flavor structure of the SMEFT operators. Besides the global analysis, we consider a large number of simpler scenarios, each with a subset of SMEFT operators, and investigate how much they improve upon the Standard Model fit. We find that the most favored scenarios, as judged by the Akaike Information Criterion, are those that involve right-handed charged currents. Additional interactions, namely oblique operators, terms modifying the Fermi constant, and operators involving right-handed neutral currents, play a role if the CDF determination of the $W$ mass is included in the analysis.
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Submitted 31 October, 2023;
originally announced November 2023.
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ALP contributions to $μ\to e$ conversion
Authors:
Kaori Fuyuto,
Emanuele Mereghetti
Abstract:
We study the $μ\to e$ conversion process in nuclear targets arising in models of axion-like particles (ALPs) with hadronic and charged lepton flavor violating (CLFV) interactions. Contributions to this process generally fall into two categories: spin-independent (SI) and spin-dependent (SD). While the SI contribution can be generated by a dipole operator through purely leptonic ALP interactions, t…
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We study the $μ\to e$ conversion process in nuclear targets arising in models of axion-like particles (ALPs) with hadronic and charged lepton flavor violating (CLFV) interactions. Contributions to this process generally fall into two categories: spin-independent (SI) and spin-dependent (SD). While the SI contribution can be generated by a dipole operator through purely leptonic ALP interactions, the SD contribution can also be present through ALP-quark interactions at tree-level. It is naively anticipated that the SI contribution would be dominant due to its coherent enhancement. In this $\textit{letter}$, we show that is not generically the case; in particular, for naturally-sized ALP couplings to quarks of order $\sim\!m_q/f_a$, the SD interaction induced by ALP-$π^0$ mixing turns out to be the leading contribution to $μ\to e$ conversion. Intuitively, this stems from the suppressed dipole contribution by the QED one-loop factor which counters the effect of SI coherent enhancement. Our study highlights the importance of $μ\to e$ conversion searches in exploring the parameter space of generic ALP models, and demonstrates the competitiveness of these searches in probing the CLFV ALP parameter space in the heavy mass range of $m_a\gtrsim m_μ$.
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Submitted 24 July, 2023;
originally announced July 2023.
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Effective field theory for radiative corrections to charged-current processes I: Vector coupling
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Emanuele Mereghetti,
Oleksandr Tomalak
Abstract:
We study radiative corrections to low-energy charged-current processes involving nucleons, such as neutron beta decay and (anti)neutrino-nucleon scattering within a top-down effective-field-theory approach. We first match the Standard Model to the low-energy effective theory valid below the weak scale and, using renormalization group equations with anomalous dimensions of…
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We study radiative corrections to low-energy charged-current processes involving nucleons, such as neutron beta decay and (anti)neutrino-nucleon scattering within a top-down effective-field-theory approach. We first match the Standard Model to the low-energy effective theory valid below the weak scale and, using renormalization group equations with anomalous dimensions of $\mathcal{O}(α, αα_s, α^2)$, evolve the resulting effective coupling down to the hadronic scale. Here, we first match to heavy-baryon chiral perturbation theory and subsequently, below the pion-mass scale, to a pionless effective theory, evolving the effective vector coupling with anomalous dimensions of $\mathcal{O}(α, α^2)$ all the way down to the scale of the electron mass, relevant for beta decays. We thus provide a new evaluation of the ``inner" radiative corrections to the vector coupling constant and to the neutron decay rate, discussing differences with the previous literature. Using our new result for the radiative corrections, we update the extraction of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ud}$ from the neutron decay.
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Submitted 6 September, 2023; v1 submitted 5 June, 2023;
originally announced June 2023.
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The case for an EIC Theory Alliance: Theoretical Challenges of the EIC
Authors:
Raktim Abir,
Igor Akushevich,
Tolga Altinoluk,
Daniele Paolo Anderle,
Fatma P. Aslan,
Alessandro Bacchetta,
Baha Balantekin,
Joao Barata,
Marco Battaglieri,
Carlos A. Bertulani,
Guillaume Beuf,
Chiara Bissolotti,
Daniël Boer,
M. Boglione,
Radja Boughezal,
Eric Braaten,
Nora Brambilla,
Vladimir Braun,
Duane Byer,
Francesco Giovanni Celiberto,
Yang-Ting Chien,
Ian C. Cloët,
Martha Constantinou,
Wim Cosyn,
Aurore Courtoy
, et al. (146 additional authors not shown)
Abstract:
We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize thi…
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We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize this ambitious and impactful physics program, including how to engage a diverse and inclusive workforce. In order to address these many-fold challenges, we propose a coordinated effort involving theory groups with differing expertise is needed. We discuss the scientific goals and scope of such an EIC Theory Alliance.
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Submitted 23 May, 2023;
originally announced May 2023.
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Neutrinoless double-beta decay in the neutrino-extended Standard Model
Authors:
Wouter Dekens,
Jordy de Vries,
Emanuele Mereghetti,
Javier Menéndez,
Pablo Soriano,
Guanghui Zhou
Abstract:
We investigate neutrinoless double-beta decay ($0νββ$) in the minimal extension of the standard model of particle physics, the $ν$SM, where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We focus on the associated sterile neutrinos and argue that the usual evaluation of their contributions to $0νββ$, based on mass-dependent nuclear matrix elements, is mis…
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We investigate neutrinoless double-beta decay ($0νββ$) in the minimal extension of the standard model of particle physics, the $ν$SM, where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We focus on the associated sterile neutrinos and argue that the usual evaluation of their contributions to $0νββ$, based on mass-dependent nuclear matrix elements, is missing important contributions from neutrinos with ultrasoft and hard momenta. We identify the hadronic and nuclear matrix elements that enter the new contributions, and calculate all relevant nuclear matrix elements for $^{136}$Xe using the nuclear shell model. Finally, we illustrate the impact on $0νββ$ rates in specific neutrino mass models and show that the new contributions significantly alter the $0νββ$ rate in most parts of the $ν$SM parameter space.
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Submitted 7 March, 2023;
originally announced March 2023.
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Nucleon form factors and the pion-nucleon sigma term
Authors:
Rajan Gupta,
Tanmoy Bhattacharya,
Vincenzo Cirigliano,
Martin Hoferichter,
Yong-Chull Jang,
Balint Joo,
Emanuele Mereghetti,
Santanu Mondal,
Sungwoo Park,
Frank Winter,
Boram Yoon
Abstract:
This talk summarizes the progress made since Lattice 2021 in understanding and controlling the contributions of towers of multihadron excited states with mass gaps starting lower than of radial excitations, and in increasing our confidence in the extraction of ground state nucleon matrix elements. The most clear evidence for multihadron excited state contributions (ESC) is in axial/pseudoscalar fo…
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This talk summarizes the progress made since Lattice 2021 in understanding and controlling the contributions of towers of multihadron excited states with mass gaps starting lower than of radial excitations, and in increasing our confidence in the extraction of ground state nucleon matrix elements. The most clear evidence for multihadron excited state contributions (ESC) is in axial/pseudoscalar form factors that are required to satisfy the PCAC relation between them. The talk examines the broader question--which and how many of the theoretically allowed positive parity states $N(\textbf p)π(-\textbf p)$, $N(\textbf 0)π(\textbf 0)π(\textbf 0)$, $N(\textbf p)π(\textbf 0)$, $N(\textbf 0)π(\textbf p),\ \ldots$ make significant contributions to a given nucleon matrix element? New data for the axial, electric and magnetic form factors are presented. They continue to show trends observed in Ref[1]. The N${}^2$LO $χ$PT analysis of the ESC to the pion-nucleon sigma term, $σ_{πN}$, has been extended to include the $Δ$ as an explicit degree of freedom [2]. The conclusion reached in Ref [3] that $N π$ and $N ππ$ states each contribute about 10 MeV to $σ_{πN}$, and the consistency between the lattice result with $N π$ state included and the phenomenological estimate is not changed by this improvement.
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Submitted 19 January, 2023;
originally announced January 2023.
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Theory Techniques for Precision Physics -- Snowmass 2021 TF06 Topical Group Report
Authors:
Radja Boughezal,
Zoltan Ligeti,
Wolfgang Altmannshofer,
Supratim Das Bakshi,
Fabrizio Caola,
Mikael Chala,
Alvaro Diaz-Carmona,
Wen Chen,
Neda Darvishi,
Brian Henning,
Sebastian Jaskiewicz,
Teppei Kitahara,
Hao-Lin Li,
Xiaohui Liu,
Adam Martin,
M. R. Masouminia,
Tom Melia,
Emanuele Mereghetti,
Bernhard Mistlberger,
Christopher Murphy,
Frank Petriello,
Davison Soper,
George Sterman,
Robert Szafron,
Leonardo Vernazza
, et al. (4 additional authors not shown)
Abstract:
The wealth of experimental data collected at laboratory experiments suggests that there is some scale separation between the Standard Model (SM) and phenomena beyond the SM (BSM). New phenomena can manifest itself as small corrections to SM predictions, or as signals in processes where the SM predictions vanish or are exceedingly small. This makes precise calculations of the SM expectations essent…
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The wealth of experimental data collected at laboratory experiments suggests that there is some scale separation between the Standard Model (SM) and phenomena beyond the SM (BSM). New phenomena can manifest itself as small corrections to SM predictions, or as signals in processes where the SM predictions vanish or are exceedingly small. This makes precise calculations of the SM expectations essential, in order to maximize the sensitivity of current and forthcoming experiments to BSM physics. This topical group report highlights some past and forthcoming theory developments critical for maximizing the sensitivity of the experimental program to understanding Nature at the shortest distances.
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Submitted 20 December, 2022; v1 submitted 21 September, 2022;
originally announced September 2022.
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Theory of Neutrino Physics -- Snowmass TF11 (aka NF08) Topical Group Report
Authors:
André de Gouvêa,
Irina Mocioiu,
Saori Pastore,
Louis E. Strigari,
L. Alvarez-Ruso,
A. M. Ankowski,
A. B. Balantekin,
V. Brdar,
M. Cadeddu,
S. Carey,
J. Carlson,
M. -C. Chen,
V. Cirigliano,
W. Dekens,
P. B. Denton,
R. Dharmapalan,
L. Everett,
H. Gallagher,
S. Gardiner,
J. Gehrlein,
L. Graf,
W. C. Haxton,
O. Hen,
H. Hergert,
S. Horiuchi
, et al. (22 additional authors not shown)
Abstract:
This is the report for the topical group Theory of Neutrino Physics (TF11/NF08) for Snowmass 2021. This report summarizes the progress in the field of theoretical neutrino physics in the past decade, the current status of the field, and the prospects for the upcoming decade.
This is the report for the topical group Theory of Neutrino Physics (TF11/NF08) for Snowmass 2021. This report summarizes the progress in the field of theoretical neutrino physics in the past decade, the current status of the field, and the prospects for the upcoming decade.
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Submitted 16 September, 2022;
originally announced September 2022.
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Ab initio calculation of the $β$ decay spectrum of $^6$He
Authors:
Garrett B. King,
Alessandro Baroni,
Vincenzo Cirigliano,
Stefano Gandolfi,
Leendert Hayen,
Emanuele Mereghetti,
Saori Pastore,
Maria Piarulli
Abstract:
We calculate the $β$ spectrum in the decay of $^6$He using Quantum Monte Carlo methods with nuclear interactions derived from chiral Effective Field Theory and consistent weak vector and axial currents. We work at second order in the multipole expansion, retaining terms suppressed by $\mathcal O(q^2/m_π^2)$, where $q$ denotes low-energy scales such as the reaction's $\mathcal Q$-value or the elect…
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We calculate the $β$ spectrum in the decay of $^6$He using Quantum Monte Carlo methods with nuclear interactions derived from chiral Effective Field Theory and consistent weak vector and axial currents. We work at second order in the multipole expansion, retaining terms suppressed by $\mathcal O(q^2/m_π^2)$, where $q$ denotes low-energy scales such as the reaction's $\mathcal Q$-value or the electron energy, and $m_π$ the pion mass. We go beyond the impulse approximation by including the effects of two-body vector and axial currents. We estimate the theoretical error on the spectrum by using four potential models in the Norfolk family of local two- and three-nucleon interactions, which have different cut-off, fit two-nucleon data up to different energies and use different observables to determine the couplings in the three-body force. We find the theoretical uncertainty on the $β$ spectrum, normalized by the total rate, to be well below the permille level, and to receive contributions of comparable size from first and second order corrections in the multipole expansion. We consider corrections to the $β$ decay spectrum induced by beyond-the-Standard Model charged-current interactions in the Standard Model Effective Field Theory, with and without sterile neutrinos, and discuss the sensitivity of the next generation of experiments to these interactions.
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Submitted 22 July, 2022;
originally announced July 2022.
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Towards Precise and Accurate Calculations of Neutrinoless Double-Beta Decay: Project Scoping Workshop Report
Authors:
V. Cirigliano,
Z. Davoudi,
J. Engel,
R. J. Furnstahl,
G. Hagen,
U. Heinz,
H. Hergert,
M. Horoi,
C. W. Johnson,
A. Lovato,
E. Mereghetti,
W. Nazarewicz,
A. Nicholson,
T. Papenbrock,
S. Pastore,
M. Plumlee,
D. R. Phillips,
P. E. Shanahan,
S. R. Stroberg,
F. Viens,
A. Walker-Loud,
K. A. Wendt,
S. M. Wild
Abstract:
We present the results of a National Science Foundation (NSF) Project Scoping Workshop, the purpose of which was to assess the current status of calculations for the nuclear matrix elements governing neutrinoless double-beta decay and determine if more work on them is required. After reviewing important recent progress in the application of effective field theory, lattice quantum chromodynamics, a…
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We present the results of a National Science Foundation (NSF) Project Scoping Workshop, the purpose of which was to assess the current status of calculations for the nuclear matrix elements governing neutrinoless double-beta decay and determine if more work on them is required. After reviewing important recent progress in the application of effective field theory, lattice quantum chromodynamics, and ab initio nuclear-structure theory to double-beta decay, we discuss the state of the art in nuclear-physics uncertainty quantification and then construct a road map for work in all these areas to fully complement the increasingly sensitive experiments in operation and under development. The road map contains specific projects in theoretical and computational physics as well as an uncertainty-quantification plan that employs Bayesian Model Mixing and an analysis of correlations between double-beta-decay rates and other observables. The goal of this program is a set of accurate and precise matrix elements, in all nuclei of interest to experimentalists, delivered together with carefully assessed uncertainties. Such calculations will allow crisp conclusions from the observation or non-observation of neutrinoless double-beta decay, no matter what new physics is at play.
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Submitted 3 July, 2022;
originally announced July 2022.
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Beta-decay implications for the W-boson mass anomaly
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Emanuele Mereghetti,
Tom Tong
Abstract:
We point out the necessity to consider $β$-decay observables in resolutions of the $W$-boson anomaly in the Standard Model Effective Field Theory that go beyond pure oblique corrections. We demonstrate that present global analyses that explain the $W$-boson mass anomaly predict a large, percent-level, violation of first-row CKM unitarity. We investigate what solutions to the $W$-boson mass anomaly…
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We point out the necessity to consider $β$-decay observables in resolutions of the $W$-boson anomaly in the Standard Model Effective Field Theory that go beyond pure oblique corrections. We demonstrate that present global analyses that explain the $W$-boson mass anomaly predict a large, percent-level, violation of first-row CKM unitarity. We investigate what solutions to the $W$-boson mass anomaly survive after including $β$-decay constraints.
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Submitted 18 April, 2022;
originally announced April 2022.
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Snowmass 2021 White Paper: Charged lepton flavor violation in the tau sector
Authors:
Swagato Banerjee,
Vincenzo Cirigliano,
Mogens Dam,
Abhay Deshpande,
Luca Fiorini,
Kaori Fuyuto,
Ciprian Gal,
Tomáš Husek,
Emanuele Mereghetti,
Kevin Monsálvez-Pozo,
Haiping Peng,
Francesco Polci,
Jorge Portolés,
Armine Rostomyan,
Michel Hernández Villanueva,
Bin Yan,
Jinlong Zhang,
Xiaorong Zhou
Abstract:
Charged lepton flavor violation has long been recognized as unambiguous signature of New Physics. Here we describe the physics capabilities and discovery potential of New Physics models with charged lepton flavor violation in the tau sector as its experimental signature. Current experimental status from the B-Factory experiments BaBar, Belle and Belle II, and future prospects at Super Tau Charm Fa…
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Charged lepton flavor violation has long been recognized as unambiguous signature of New Physics. Here we describe the physics capabilities and discovery potential of New Physics models with charged lepton flavor violation in the tau sector as its experimental signature. Current experimental status from the B-Factory experiments BaBar, Belle and Belle II, and future prospects at Super Tau Charm Factory, LHC, EIC and FCC-ee experiments to discover New Physics via charged lepton flavor violation in the tau sector are discussed in detail.
Submitted to the Proceedings of the US Community Study on the Future of Particle Physics (Snowmass 2021)
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Submitted 26 May, 2022; v1 submitted 28 March, 2022;
originally announced March 2022.
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The pion-nucleon sigma term from Lattice QCD
Authors:
Rajan Gupta,
Tanmoy Bhattacharya,
Martin Hoferichter,
Emanuele Mereghetti,
Sungwoo Park,
Boram Yoon
Abstract:
We summarize recent evidence, both from lattice QCD and chiral perturbation theory, that suggests that larger-than-expected excited-state contamination could be the reason for the tension between phenomenological determinations and previous direct lattice-QCD calculations of the pion--nucleon sigma term $σ_{πN}$. In addition, we extend the $χ$PT analysis by calculating the corrections due to inclu…
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We summarize recent evidence, both from lattice QCD and chiral perturbation theory, that suggests that larger-than-expected excited-state contamination could be the reason for the tension between phenomenological determinations and previous direct lattice-QCD calculations of the pion--nucleon sigma term $σ_{πN}$. In addition, we extend the $χ$PT analysis by calculating the corrections due to including the $Δ(1232)$ resonance as an explicit degree of freedom. This correction is found to be small, thereby corroborating the excited-state effects found in the $Δ$-less calculation and the result for $σ_{πN}$.
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Submitted 25 March, 2022;
originally announced March 2022.
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Neutrinoless Double-Beta Decay: A Roadmap for Matching Theory to Experiment
Authors:
Vincenzo Cirigliano,
Zohreh Davoudi,
Wouter Dekens,
Jordy de Vries,
Jonathan Engel,
Xu Feng,
Julia Gehrlein,
Michael L. Graesser,
Lukáš Gráf,
Heiko Hergert,
Luchang Jin,
Emanuele Mereghetti,
Amy Nicholson,
Saori Pastore,
Michael J. Ramsey-Musolf,
Richard Ruiz,
Martin Spinrath,
Ubirajara van Kolck,
André Walker-Loud
Abstract:
The observation of neutrino oscillations and hence non-zero neutrino masses provided a milestone in the search for physics beyond the Standard Model. But even though we now know that neutrinos are massive, the nature of neutrino masses, i.e., whether they are Dirac or Majorana, remains an open question. A smoking-gun signature of Majorana neutrinos is the observation of neutrinoless double-beta de…
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The observation of neutrino oscillations and hence non-zero neutrino masses provided a milestone in the search for physics beyond the Standard Model. But even though we now know that neutrinos are massive, the nature of neutrino masses, i.e., whether they are Dirac or Majorana, remains an open question. A smoking-gun signature of Majorana neutrinos is the observation of neutrinoless double-beta decay, a process that violates the lepton-number conservation of the Standard Model. This white paper focuses on the theoretical aspects of the neutrinoless double-beta decay program and lays out a roadmap for future developments. The roadmap is a multi-scale path starting from high-energy models of neutrinoless double-beta decay all the way to the low-energy nuclear many-body problem that needs to be solved to supplement measurements of the decay rate. The path goes through a systematic effective-field-theory description of the underlying processes at various scales and needs to be supplemented by lattice quantum chromodynamics input. The white paper also discusses the interplay between neutrinoless double-beta decay, experiments at the Large Hadron Collider and results from astrophysics and cosmology in probing simplified models of lepton-number violation at the TeV scale, and the generation of the matter-antimatter asymmetry via leptogenesis. This white paper is prepared for the topical groups TF11 (Theory of Neutrino Physics), TF05 (Lattice Gauge Theory), RF04 (Baryon and Lepton Number Violating Processes), NF03 (Beyond the Standard Model) and NF05 (Neutrino Properties) within the Theory Frontier, Rare Processes and Precision Frontier, and Neutrino Physics Frontier of the U.S. Community Study on the Future of Particle Physics (Snowmass 2021).
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Submitted 22 March, 2022;
originally announced March 2022.
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Electric dipole moments and the search for new physics
Authors:
Ricardo Alarcon,
Jim Alexander,
Vassilis Anastassopoulos,
Takatoshi Aoki,
Rick Baartman,
Stefan Baeßler,
Larry Bartoszek,
Douglas H. Beck,
Franco Bedeschi,
Robert Berger,
Martin Berz,
Hendrick L. Bethlem,
Tanmoy Bhattacharya,
Michael Blaskiewicz,
Thomas Blum,
Themis Bowcock,
Anastasia Borschevsky,
Kevin Brown,
Dmitry Budker,
Sergey Burdin,
Brendan C. Casey,
Gianluigi Casse,
Giovanni Cantatore,
Lan Cheng,
Timothy Chupp
, et al. (118 additional authors not shown)
Abstract:
Static electric dipole moments of nondegenerate systems probe mass scales for physics beyond the Standard Model well beyond those reached directly at high energy colliders. Discrimination between different physics models, however, requires complementary searches in atomic-molecular-and-optical, nuclear and particle physics. In this report, we discuss the current status and prospects in the near fu…
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Static electric dipole moments of nondegenerate systems probe mass scales for physics beyond the Standard Model well beyond those reached directly at high energy colliders. Discrimination between different physics models, however, requires complementary searches in atomic-molecular-and-optical, nuclear and particle physics. In this report, we discuss the current status and prospects in the near future for a compelling suite of such experiments, along with developments needed in the encompassing theoretical framework.
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Submitted 4 April, 2022; v1 submitted 15 March, 2022;
originally announced March 2022.
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Theoretical developments in the SMEFT at dimension-8 and beyond
Authors:
Simone Alioli,
Radja Boughezal,
Weiguang Cao,
Mikael Chala,
Álvaro Díaz-Carmona,
Supratim Das Bakshi,
Gauthier Durieux,
Lukáš Gráf,
Guilherme Guedes,
Brian Quinn Henning,
Teppei Kitahara,
Hao-Lin Li,
Xiaochuan Lu,
Camila S. Machado,
Adam Martin,
Tom Melia,
Emanuele Mereghetti,
Hitoshi Murayama,
Christopher W. Murphy,
Jasper Roosmale Nepveu,
Sridip Pal,
Frank Petriello,
Yael Shadmi,
Jing Shu,
Yaniv Weiss
, et al. (2 additional authors not shown)
Abstract:
In this contribution to the Snowmass 2021 process we review theoretical developments in the Standard Model Effective Field Theory (SMEFT) with a focus on effects at the dimension-8 level and beyond. We review the theoretical advances that led to the complete construction of the operator bases for the dimension-8 and dimension-9 SMEFT Lagrangians. We discuss the possibility of obtaining all-orders…
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In this contribution to the Snowmass 2021 process we review theoretical developments in the Standard Model Effective Field Theory (SMEFT) with a focus on effects at the dimension-8 level and beyond. We review the theoretical advances that led to the complete construction of the operator bases for the dimension-8 and dimension-9 SMEFT Lagrangians. We discuss the possibility of obtaining all-orders results in the $1/Λ$ expansion for certain SMEFT observables as well as the current status of renormalization group running and implications for positivity, and briefly present the on-shell approach to constructing SMEFT amplitudes. Finally we present several new phenomenological effects that first arise at dimension-8 and discuss the impact of these terms on experimental analyses.
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Submitted 2 April, 2022; v1 submitted 13 March, 2022;
originally announced March 2022.
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Pion-induced radiative corrections to neutron beta-decay
Authors:
Vincenzo Cirigliano,
Jordy de Vries,
Leendert Hayen,
Emanuele Mereghetti,
André Walker-Loud
Abstract:
We compute the electromagnetic corrections to neutron beta decay using a low-energy hadronic effective field theory. We identify and compute new radiative corrections arising from virtual pions that were missed in previous studies. The largest correction is a percent-level shift in the axial charge of the nucleon proportional to the electromagnetic part of the pion-mass splitting. Smaller correcti…
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We compute the electromagnetic corrections to neutron beta decay using a low-energy hadronic effective field theory. We identify and compute new radiative corrections arising from virtual pions that were missed in previous studies. The largest correction is a percent-level shift in the axial charge of the nucleon proportional to the electromagnetic part of the pion-mass splitting. Smaller corrections, comparable to anticipated experimental precision, impact the $β$-$ν$ angular correlations and the $β$-asymmetry. We comment on implications of our results for the comparison of the experimentally measured axial charge with first-principle computations using lattice QCD and on the potential of $β$-decay experiments to constrain beyond-the-Standard-Model interactions.
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Submitted 21 February, 2022;
originally announced February 2022.
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One-loop matching for quark dipole operators in a gradient-flow scheme
Authors:
Emanuele Mereghetti,
Christopher J. Monahan,
Matthew D. Rizik,
Andrea Shindler,
Peter Stoffer
Abstract:
The quark chromoelectric dipole (qCEDM) operator is a CP-violating operator describing, at hadronic energies, beyond-the-standard-model contributions to the electric dipole moment of particles with nonzero spin. In this paper we define renormalized dipole operators in a regularization-independent scheme using the gradient flow, and we perform the matching at one loop in perturbation theory to reno…
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The quark chromoelectric dipole (qCEDM) operator is a CP-violating operator describing, at hadronic energies, beyond-the-standard-model contributions to the electric dipole moment of particles with nonzero spin. In this paper we define renormalized dipole operators in a regularization-independent scheme using the gradient flow, and we perform the matching at one loop in perturbation theory to renormalized operators of the same and lower dimension in the more familiar MS scheme. We also determine the matching coefficients for the quark chromomagnetic dipole operator (qCMDM), which contributes, for example, to matrix elements relevant to CP-violating and CP-conserving kaon decays. The calculation provides a basis for future lattice QCD computations of hadronic matrix elements of the qCEDM and qCMDM operators.
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Submitted 13 April, 2022; v1 submitted 22 November, 2021;
originally announced November 2021.
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A low-energy perspective on the minimal left-right symmetric model
Authors:
Wouter Dekens,
Lorenzo Andreoli,
Jordy de Vries,
Emanuele Mereghetti,
Femke Oosterhof
Abstract:
We perform a global analysis of the low-energy phenomenology of the minimal left-right symmetric model (mLRSM) with parity symmetry. We match the mLRSM to the Standard Model Effective Field Theory Lagrangian at the left-right-symmetry breaking scale and perform a comprehensive fit to low-energy data including mesonic, neutron, and nuclear $β$-decay processes, $ΔF=1$ and $ΔF=2$ CP-even and -odd pro…
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We perform a global analysis of the low-energy phenomenology of the minimal left-right symmetric model (mLRSM) with parity symmetry. We match the mLRSM to the Standard Model Effective Field Theory Lagrangian at the left-right-symmetry breaking scale and perform a comprehensive fit to low-energy data including mesonic, neutron, and nuclear $β$-decay processes, $ΔF=1$ and $ΔF=2$ CP-even and -odd processes in the bottom and strange sectors, and electric dipole moments (EDMs) of nucleons, nuclei, and atoms. We fit the Cabibbo-Kobayashi-Maskawa and mLRSM parameters simultaneously and determine a lower bound on the mass of the right-handed $W_R$ boson. In models where a Peccei-Quinn mechanism provides a solution to the strong CP problem, we obtain $M_{W_R} \gtrsim 5.5$ TeV at $95\%$ C.L. which can be significantly improved with next-generation EDM experiments. In the $P$-symmetric mLRSM without a Peccei-Quinn mechanism we obtain a more stringent constraint $M_{W_R} \gtrsim 17$ TeV at $95\%$ C.L., which is difficult to improve with low-energy measurements alone. In all cases, the additional scalar fields of the mLRSM are required to be a few times heavier than the right-handed gauge bosons. We consider a recent discrepancy in tests of first-row unitarity of the CKM matrix. We find that, while TeV-scale $W_R$ bosons can alleviate some of the tension found in the $V_{ud,us}$ determinations, a solution to the discrepancy is disfavored when taking into account other low-energy observables within the mLRSM.
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Submitted 3 December, 2021; v1 submitted 22 July, 2021;
originally announced July 2021.
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Dilepton production in the SMEFT at $\mathcal O(1/Λ^4)$
Authors:
Radja Boughezal,
Emanuele Mereghetti,
Frank Petriello
Abstract:
We study the inclusion of $\mathcal O(1/Λ^4)$ effects in the Standard Model Effective Field Theory in fits to the current Drell-Yan data at the LHC. Our analysis includes the full set of dimension-6 and dimension-8 operators contributing to the dilepton process, and is performed to next-to-leading-order in the QCD coupling constant at both $\mathcal O(1/Λ^2)$ and $\mathcal O(1/Λ^4)$. We find that…
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We study the inclusion of $\mathcal O(1/Λ^4)$ effects in the Standard Model Effective Field Theory in fits to the current Drell-Yan data at the LHC. Our analysis includes the full set of dimension-6 and dimension-8 operators contributing to the dilepton process, and is performed to next-to-leading-order in the QCD coupling constant at both $\mathcal O(1/Λ^2)$ and $\mathcal O(1/Λ^4)$. We find that the inclusion of dimension-6 squared terms and certain dimension-8 operators has significant effects on fits to the current data. Neglecting them leads to bounds on dimension-6 operators off by large factors. We find that dimension-8 four-fermion operators can already be probed to the several-TeV level by LHC results, and that their inclusion significantly changes the limits found for dimension-6 operators. We discuss which dimension-8 operators should be included in fits to the LHC data. Only a manageable subset of two-derivative dimension-8 four-fermion operators need to be included at this stage given current LHC uncertainties.
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Submitted 9 May, 2022; v1 submitted 9 June, 2021;
originally announced June 2021.
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The pion-nucleon sigma term from lattice QCD
Authors:
Rajan Gupta,
Sungwoo Park,
Martin Hoferichter,
Emanuele Mereghetti,
Boram Yoon,
Tanmoy Bhattacharya
Abstract:
We present an analysis of the pion-nucleon $σ$-term, $σ_{πN}$, using six ensembles with 2+1+1-flavor highly improved staggered quark action generated by the MILC collaboration. The most serious systematic effect in lattice calculations of nucleon correlation functions is the contribution of excited states. We estimate these using chiral perturbation theory ($χ$PT), and show that the leading contri…
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We present an analysis of the pion-nucleon $σ$-term, $σ_{πN}$, using six ensembles with 2+1+1-flavor highly improved staggered quark action generated by the MILC collaboration. The most serious systematic effect in lattice calculations of nucleon correlation functions is the contribution of excited states. We estimate these using chiral perturbation theory ($χ$PT), and show that the leading contribution to the isoscalar scalar charge comes from N$π$ and N$ππ$ states. Therefore, we carry out two analyses of lattice data to remove excited-state contamination, the standard one and a new one including N$π$ and N$ππ$ states. We find that the standard analysis gives $σ_{πN} = 41.9(4.9)$ MeV, consistent with previous lattice calculations, while our preferred $χ$PT-motivated analysis gives $σ_{πN} = 59.6(7.4)$ MeV, which is consistent with phenomenological values obtained using $π$N scattering data. Our data on one physical pion mass ensemble was crucial for exposing this difference, therefore, calculations on additional physical mass ensembles are needed to confirm our result and resolve the tension between lattice QCD and phenomenology.
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Submitted 16 December, 2021; v1 submitted 25 May, 2021;
originally announced May 2021.
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Leptonic anomalous magnetic moments in $ν$SMEFT
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Kaori Fuyuto,
Emanuele Mereghetti,
Richard Ruiz
Abstract:
We investigate contributions to the anomalous magnetic moments of charged leptons in the neutrino-extended Standard Model Effective Field Theory ($ν$SMEFT). We discuss how $ν$SMEFT operators can contribute to a lepton's magnetic moment at one- and two-loop order. We show that only one operator can account for existing electronic and muonic discrepancies, assuming new physics appears above $1$ TeV.…
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We investigate contributions to the anomalous magnetic moments of charged leptons in the neutrino-extended Standard Model Effective Field Theory ($ν$SMEFT). We discuss how $ν$SMEFT operators can contribute to a lepton's magnetic moment at one- and two-loop order. We show that only one operator can account for existing electronic and muonic discrepancies, assuming new physics appears above $1$ TeV. In particular, we find that a right-handed charged current in combination with minimal sterile-active mixing can explain the discrepancy for sterile neutrino masses of $\mathcal O(100)$ GeV while avoiding direct and indirect constraints. We discuss how searches for sterile neutrino production at the (HL-)LHC, measurements of $h\rightarrow μ^+ μ^-$ and searches for $h\rightarrow e^+ e^-$, neutrinoless double beta decay experiments, and improved unitarity tests of the CKM matrix can further probe the relevant parameter space.
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Submitted 23 September, 2021; v1 submitted 24 May, 2021;
originally announced May 2021.
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Charged Lepton Flavor Violation at the EIC
Authors:
Vincenzo Cirigliano,
Kaori Fuyuto,
Christopher Lee,
Emanuele Mereghetti,
Bin Yan
Abstract:
We present a comprehensive analysis of the potential sensitivity of the Electron-Ion Collider (EIC) to charged lepton flavor violation (CLFV) in the channel $ep\to τX$, within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). We compute the relevant cross sections to leading order in QCD and electroweak corrections and perform simulations of signal and SM backgr…
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We present a comprehensive analysis of the potential sensitivity of the Electron-Ion Collider (EIC) to charged lepton flavor violation (CLFV) in the channel $ep\to τX$, within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). We compute the relevant cross sections to leading order in QCD and electroweak corrections and perform simulations of signal and SM background events in various $τ$ decay channels, suggesting simple cuts to enhance the associated estimated efficiencies. To assess the discovery potential of the EIC in $τ$-$e$ transitions, we study the sensitivity of other probes of this physics across a broad range of energy scales, from $pp \to e τX$ at the Large Hadron Collider to decays of $B$ mesons and $τ$ leptons, such as $τ\to e γ$, $τ\to e \ell^+ \ell^-$, and crucially the hadronic modes $τ\to e Y$ with $Y \in \{ π, K, ππ, K π, ...\}$. We find that electroweak dipole and four-fermion semi-leptonic operators involving light quarks are already strongly constrained by $τ$ decays, while operators involving the $c$ and $b$ quarks present more promising discovery potential for the EIC. An analysis of three models of leptoquarks confirms the expectations based on the SMEFT results. We also identify future directions needed to maximize the reach of the EIC in CLFV searches: these include an optimization of the $τ$ tagger in hadronic channels, an exploration of background suppression through tagging $b$ and $c$ jets in the final state, and a global fit by turning on all SMEFT couplings, which will likely reveal new discovery windows for the EIC.
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Submitted 27 July, 2021; v1 submitted 11 February, 2021;
originally announced February 2021.
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Determining the leading-order contact term in neutrinoless double $\boldsymbolβ$ decay
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Martin Hoferichter,
Emanuele Mereghetti
Abstract:
We present a method to determine the leading-order (LO) contact term contributing to the $nn \to pp e^-e^-$ amplitude through the exchange of light Majorana neutrinos. Our approach is based on the representation of the amplitude as the momentum integral of a known kernel (proportional to the neutrino propagator) times the generalized forward Compton scattering amplitude…
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We present a method to determine the leading-order (LO) contact term contributing to the $nn \to pp e^-e^-$ amplitude through the exchange of light Majorana neutrinos. Our approach is based on the representation of the amplitude as the momentum integral of a known kernel (proportional to the neutrino propagator) times the generalized forward Compton scattering amplitude $n(p_1) n(p_2) W^+ (k) \to p(p_1^\prime) p(p_2^\prime) W^- (k)$, in analogy to the Cottingham formula for the electromagnetic contribution to hadron masses. We construct model-independent representations of the integrand in the low- and high-momentum regions, through chiral EFT and the operator product expansion, respectively. We then construct a model for the full amplitude by interpolating between these two regions, using appropriate nucleon factors for the weak currents and information on nucleon-nucleon ($N\! N$) scattering in the $^1S_0$ channel away from threshold. By matching the amplitude obtained in this way to the LO chiral EFT amplitude we obtain the relevant LO contact term and discuss various sources of uncertainty. We validate the approach by computing the analog $I = 2$ $N\! N$ contact term and by reproducing, within uncertainties, the charge-independence-breaking contribution to the $^1S_0$ $N\! N$ scattering lengths. While our analysis is performed in the $\overline{\rm MS}$ scheme, we express our final result in terms of the scheme-independent renormalized amplitude ${\cal A}_ν(|{\bf p}|,|{\bf p}^\prime|)$ at a set of kinematic points near threshold. We illustrate for two cutoff schemes how, using our synthetic data for ${\cal A}_ν$, one can determine the contact-term contribution in any regularization scheme, in particular the ones employed in nuclear-structure calculations for isotopes of experimental interest.
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Submitted 8 June, 2021; v1 submitted 5 February, 2021;
originally announced February 2021.
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Contribution of the QCD $Θ$-term to nucleon electric dipole moment
Authors:
Tanmoy Bhattacharya,
Vincenzo Cirigliano,
Rajan Gupta,
Emanuele Mereghetti,
Boram Yoon
Abstract:
We present a calculation of the contribution of the $Θ$-term to the neutron and proton electric dipole moments using seven 2+1+1-flavor HISQ ensembles. We also estimate the topological susceptibility for the 2+1+1 theory to be $χ_Q = (66(9)(4) \rm MeV)^4$ in the continuum limit at $M_π= 135$ MeV. The calculation of the nucleon three-point function is done using Wilson-clover valence quarks. The CP…
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We present a calculation of the contribution of the $Θ$-term to the neutron and proton electric dipole moments using seven 2+1+1-flavor HISQ ensembles. We also estimate the topological susceptibility for the 2+1+1 theory to be $χ_Q = (66(9)(4) \rm MeV)^4$ in the continuum limit at $M_π= 135$ MeV. The calculation of the nucleon three-point function is done using Wilson-clover valence quarks. The CP-violating form factor $F_3$ is calculated by expanding in small $Θ$. We show that lattice artifacts introduce a term proportional to $a$ that does not vanish in the chiral limit, and we include this in our chiral-continuum fits. A chiral perturbation theory analysis shows that the $N(0) π(0)$ state should provide the leading excited state contribution, and we study the effect of such a state. Detailed analysis of the contributions to the neutron and proton electric dipole moment using two strategies for removing excited state contamination are presented. Using the excited state spectrum from fits to the two-point function, we find $d_n^Θ$ is small, $|d_n^Θ| \lesssim 0.01 \overline Θe$ fm, whereas for the proton we get $|d_p^Θ| \sim 0.02 \overline Θe$ fm. On the other hand, if the dominant excited-state contribution is from the $N π$ state, then $|d_n^Θ|$ could be as large as $0.05 \overline Θe$ fm and $|d_p^Θ| \sim 0.07 \overline Θe$ fm. Our overall conclusion is that present lattice QCD calculations do not provide a reliable estimate of the contribution of the $Θ$-term to the nucleon electric dipole moments, and a factor of ten higher statistics data are needed to get better control over the systematics and possibly a $3σ$ result.
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Submitted 18 January, 2021;
originally announced January 2021.
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Towards complete leading-order predictions for neutrinoless double $β$ decay
Authors:
Vincenzo Cirigliano,
Wouter Dekens,
Jordy de Vries,
Martin Hoferichter,
Emanuele Mereghetti
Abstract:
The amplitude for the neutrinoless double $β$ ($0νββ$) decay of the two-neutron system, $nn\to ppe^-e^-$, constitutes a key building block for nuclear-structure calculations of heavy nuclei employed in large-scale $0νββ$ searches. Assuming that the $0νββ$ process is mediated by a light-Majorana-neutrino exchange, a systematic analysis in chiral effective field theory shows that already at leading…
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The amplitude for the neutrinoless double $β$ ($0νββ$) decay of the two-neutron system, $nn\to ppe^-e^-$, constitutes a key building block for nuclear-structure calculations of heavy nuclei employed in large-scale $0νββ$ searches. Assuming that the $0νββ$ process is mediated by a light-Majorana-neutrino exchange, a systematic analysis in chiral effective field theory shows that already at leading order a contact operator is required to ensure renormalizability. In this work, we develop a method to estimate the numerical value of its coefficient in analogy to the Cottingham formula and validate the result by reproducing the charge-independence-breaking contribution to the nucleon-nucleon scattering lengths. Our central result, while derived in the $\overline{\text{MS}}$ scheme, is given in terms of the renormalized amplitude $\mathcal{A}_ν(|\mathbf{p}|,|\mathbf{p}^\prime|)$, matching to which will allow one to determine the contact-term contribution in regularization schemes employed in nuclear-structure calculations. Our results thus greatly reduce a crucial uncertainty in the interpretation of searches for $0νββ$ decay.
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Submitted 30 April, 2021; v1 submitted 21 December, 2020;
originally announced December 2020.
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Electric dipole moments of three-nucleon systems in the pionless effective field theory
Authors:
Zichao Yang,
Emanuele Mereghetti,
Lucas Platter,
Matthias R. Schindler,
Jared Vanasse
Abstract:
We calculate the electric dipole moments (EDMs) of three-nucleon systems at leading order in pionless effective field theory. The one-body contributions that arise from permanent proton and neutron EDMs and the two-body contributions that arise from CP-odd nucleon-nucleon interactions are taken into account. Neglecting the Coulomb interaction, we consider the triton and ${}^3$He, and also investig…
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We calculate the electric dipole moments (EDMs) of three-nucleon systems at leading order in pionless effective field theory. The one-body contributions that arise from permanent proton and neutron EDMs and the two-body contributions that arise from CP-odd nucleon-nucleon interactions are taken into account. Neglecting the Coulomb interaction, we consider the triton and ${}^3$He, and also investigate them in the Wigner-SU(4) symmetric limit. We also calculate the electric dipole form factor and find numerically that the momentum dependence of the electric dipole form factor in the Wigner limit is, up to an overall constant (and numerical accuracy), the same as the momentum dependence of the charge form factor.
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Submitted 3 November, 2020;
originally announced November 2020.
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Non-perturbative renormalization scheme for the CP-odd three-gluon operator
Authors:
Vincenzo Cirigliano,
Emanuele Mereghetti,
Peter Stoffer
Abstract:
We define a regularization-independent momentum-subtraction scheme for the $CP$-odd three-gluon operator at dimension six. This operator appears in effective field theories for heavy physics beyond the Standard Model, describing the indirect effect of new sources of $CP$-violation at low energies. In a hadronic context, it induces permanent electric dipole moments. The hadronic matrix elements of…
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We define a regularization-independent momentum-subtraction scheme for the $CP$-odd three-gluon operator at dimension six. This operator appears in effective field theories for heavy physics beyond the Standard Model, describing the indirect effect of new sources of $CP$-violation at low energies. In a hadronic context, it induces permanent electric dipole moments. The hadronic matrix elements of the three-gluon operator are non-perturbative objects that should ideally be evaluated with lattice QCD. We define a non-perturbative renormalization scheme that can be implemented on the lattice and we compute the scheme transformation to $\overline{\text{MS}}$ at one loop. Our calculation can be used as an interface to future lattice-QCD calculations of the matrix elements of the three-gluon operator, in order to obtain theoretically robust constraints on physics beyond the Standard Model from measurements of the neutron electric dipole moment.
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Submitted 14 September, 2020; v1 submitted 7 April, 2020;
originally announced April 2020.
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Novel angular dependence in Drell-Yan lepton production via dimension-8 operators
Authors:
Simone Alioli,
Radja Boughezal,
Emanuele Mereghetti,
Frank Petriello
Abstract:
We study the effects of dimension-8 operators on Drell-Yan production of lepton pairs at the Large Hadron Collider (LHC). We identify a class of operators that leads to novel angular dependence not accounted for in current analyses. The observation of such effects would be a smoking-gun signature of new physics appearing at the dimension-8 level. We propose an extension of the currently used angul…
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We study the effects of dimension-8 operators on Drell-Yan production of lepton pairs at the Large Hadron Collider (LHC). We identify a class of operators that leads to novel angular dependence not accounted for in current analyses. The observation of such effects would be a smoking-gun signature of new physics appearing at the dimension-8 level. We propose an extension of the currently used angular basis and show that these effects should be observable in future LHC analyses for realistic values of the associated dimension-8 Wilson coefficients.
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Submitted 25 March, 2020;
originally announced March 2020.
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Sterile neutrinos and neutrinoless double beta decay in effective field theory
Authors:
Wouter Dekens,
Jordy de Vries,
Kaori Fuyuto,
Emanuele Mereghetti,
Guanghui Zhou
Abstract:
We investigate neutrinoless double beta decay ($0νββ$) in the presence of sterile neutrinos with Majorana mass terms. These gauge-singlet fields are allowed to interact with Standard-Model (SM) fields via renormalizable Yukawa couplings as well as higher-dimensional gauge-invariant operators up to dimension seven in the Standard Model Effective Field Theory extended with sterile neutrinos. At the…
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We investigate neutrinoless double beta decay ($0νββ$) in the presence of sterile neutrinos with Majorana mass terms. These gauge-singlet fields are allowed to interact with Standard-Model (SM) fields via renormalizable Yukawa couplings as well as higher-dimensional gauge-invariant operators up to dimension seven in the Standard Model Effective Field Theory extended with sterile neutrinos. At the GeV scale, we use Chiral effective field theory involving sterile neutrinos to connect the operators at the level of quarks and gluons to hadronic interactions involving pions and nucleons. This allows us to derive an expression for $0νββ$ rates for various isotopes in terms of phase-space factors, hadronic low-energy constants, nuclear matrix elements, the neutrino masses, and the Wilson coefficients of higher-dimensional operators. The needed hadronic low-energy constants and nuclear matrix elements depend on the neutrino masses, for which we obtain interpolation formulae grounded in QCD and chiral perturbation theory that improve existing formulae that are only valid in a small regime of neutrino masses. The resulting framework can be used directly to assess the impact of $0νββ$ experiments on scenarios with light sterile neutrinos and should prove useful in global analyses of sterile-neutrino searches. We perform several phenomenological studies of $0νββ$ in the presence of sterile neutrinos with and without higher-dimensional operators. We find that non-standard interactions involving sterile neutrinos have a dramatic impact on $0νββ$ phenomenology, and next-generation experiments can probe such interactions up to scales of $\mathcal O(100)$ TeV.
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Submitted 13 June, 2020; v1 submitted 17 February, 2020;
originally announced February 2020.
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Parity- and time-reversal-violating nuclear forces
Authors:
J. de Vries,
E. Epelbaum,
L. Girlanda,
A. Gnech,
E. Mereghetti,
M. Viviani
Abstract:
Parity-violating and time-reversal conserving (PVTC) and parity-violating and time-reversal-violating (PVTV) forces in nuclei form only a tiny component of the total interaction between nucleons. The study of these tiny forces can nevertheless be of extreme interest because they allow to obtain information on fundamental symmetries using nuclear systems. The PVTC interaction derives from the weak…
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Parity-violating and time-reversal conserving (PVTC) and parity-violating and time-reversal-violating (PVTV) forces in nuclei form only a tiny component of the total interaction between nucleons. The study of these tiny forces can nevertheless be of extreme interest because they allow to obtain information on fundamental symmetries using nuclear systems. The PVTC interaction derives from the weak interaction between the quarks inside nucleons and nuclei and the study of PVTC effects opens a window on the quark-quark weak interaction. The PVTV interaction is sensitive to more exotic interactions at the fundamental level, in particular to strong CP violation in the Standard Model Lagrangian, or even to exotic phenomena predicted in various beyond-the-Standard-Model scenarios. The presence of these interactions can be revealed either by studying various asymmetries in polarized scattering of nuclear systems, or by measuring the presence of non-vanishing permanent electric dipole moments of nucleons, nuclei and diamagnetic atoms and molecules. In this contribution, we review the derivation of the nuclear PVTC and PVTV interactions within various frameworks. We focus in particular on the application of chiral effective field theory, which allows for a more strict connection with the fundamental interactions at the quark level. We investigate PVTC and PVTV effects induced by these potential on several few-nucleon observables, such as the longitudinal asymmetry in proton-proton scattering and radiative neutron-proton capture, and the electric dipole momentsof the deuteron and the trinucleon system.
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Submitted 24 January, 2020;
originally announced January 2020.
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Towards grounding nuclear physics in QCD
Authors:
Christian Drischler,
Wick Haxton,
Kenneth McElvain,
Emanuele Mereghetti,
Amy Nicholson,
Pavlos Vranas,
André Walker-Loud
Abstract:
Exascale computing could soon enable a predictive theory of nuclear structure and reactions rooted in the Standard Model, with quantifiable and systematically improvable uncertainties. Such a predictive theory will help exploit experiments that use nucleons and nuclei as laboratories for testing the Standard Model and its limitations. Examples include direct dark matter detection, neutrinoless dou…
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Exascale computing could soon enable a predictive theory of nuclear structure and reactions rooted in the Standard Model, with quantifiable and systematically improvable uncertainties. Such a predictive theory will help exploit experiments that use nucleons and nuclei as laboratories for testing the Standard Model and its limitations. Examples include direct dark matter detection, neutrinoless double beta decay, and searches for permanent electric dipole moments of the neutron and atoms. It will also help connect QCD to the properties of cold neutron stars and hot supernova cores. We discuss how a quantitative bridge between QCD and the properties of nuclei and nuclear matter will require a synthesis of lattice QCD (especially as applied to two- and three-nucleon interactions), effective field theory, and ab initio methods for solving the nuclear many-body problem. While there are significant challenges that must be addressed in developing this triad of theoretical tools, the rapid advance of computing is accelerating progress. In particular, we focus this review on the anticipated advances from lattice QCD and how these advances will impact few-body effective theories of nuclear physics by providing critical input, such as constraints on unknown low-energy constants of the effective (field) theories. We also review particular challenges that must be overcome for the successful application of lattice QCD for low-energy nuclear physics. We describe progress in developing few-body effective (field) theories of nuclear physics, with an emphasis on HOBET, a non-relativistic effective theory of nuclear physics, which is less common in the literature. We use the examples of neutrinoless double beta decay and the nuclear-matter equation of state to illustrate how the coupling of lattice QCD to effective theory might impact our understanding of symmetries and exotic astrophysical environments.
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Submitted 19 August, 2021; v1 submitted 17 October, 2019;
originally announced October 2019.
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A renormalized approach to neutrinoless double-beta decay
Authors:
V. Cirigliano,
W. Dekens,
J. de Vries,
M. L. Graesser,
E. Mereghetti,
S. Pastore,
M. Piarulli,
U. van Kolck,
R. B. Wiringa
Abstract:
The process at the heart of neutrinoless double-beta decay, $nn \rightarrow p p\, e^- e^-$ induced by a light Majorana neutrino, is investigated in pionless and chiral effective field theory. We show in various regularization schemes the need to introduce a short-range lepton-number-violating operator at leading order, confirming earlier findings. We demonstrate that such a short-range operator is…
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The process at the heart of neutrinoless double-beta decay, $nn \rightarrow p p\, e^- e^-$ induced by a light Majorana neutrino, is investigated in pionless and chiral effective field theory. We show in various regularization schemes the need to introduce a short-range lepton-number-violating operator at leading order, confirming earlier findings. We demonstrate that such a short-range operator is only needed in spin-singlet $S$-wave transitions, while leading-order transitions involving higher partial waves depend solely on long-range currents. Calculations are extended to include next-to-leading corrections in perturbation theory, where to this order no additional undetermined parameters appear. We establish a connection based on chiral symmetry between neutrinoless double-beta decay and nuclear charge-independence breaking induced by electromagnetism. Data on the latter confirm the need for a leading-order short-range operator, but do not allow for a full determination of the corresponding lepton-number-violating coupling. Using a crude estimate of this coupling, we perform ab initio calculations of the matrix elements for neutrinoless double-beta decay for $^6$He and $^{12}$Be. We speculate on the phenomenological impact of the leading short-range operator on the basis of these results.
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Submitted 25 July, 2019;
originally announced July 2019.
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Proposal for the validation of Monte Carlo implementations of the standard model effective field theory
Authors:
Gauthier Durieux,
Ilaria Brivio,
Fabio Maltoni,
Michael Trott,
Simone Alioli,
Andy Buckley,
Mauro Chiesa,
Jorge de Blas,
Athanasios Dedes,
Céline Degrande,
Ansgar Denner,
Christoph Englert,
James Ferrando,
Benjamin Fuks,
Peter Galler,
Admir Greljo,
Valentin Hirschi,
Gino Isidori,
Wolfgang Kilian,
Frank Krauss,
Jean-Nicolas Lang,
Jonas Lindert,
Michelangelo Mangano,
David Marzocca,
Olivier Mattelaer
, et al. (16 additional authors not shown)
Abstract:
We propose a procedure to cross-validate Monte Carlo implementations of the standard model effective field theory. It is based on the numerical comparison of squared amplitudes computed at specific phase-space and parameter points in pairs of implementations. Interactions are fully linearised in the effective field theory expansion. The squares of linear effective field theory amplitudes and their…
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We propose a procedure to cross-validate Monte Carlo implementations of the standard model effective field theory. It is based on the numerical comparison of squared amplitudes computed at specific phase-space and parameter points in pairs of implementations. Interactions are fully linearised in the effective field theory expansion. The squares of linear effective field theory amplitudes and their interference with standard-model contributions are compared separately. Such pairwise comparisons are primarily performed at tree level and a possible extension to the one-loop level is also briefly considered. We list the current standard model effective field theory implementations and the comparisons performed to date.
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Submitted 28 June, 2019;
originally announced June 2019.
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$\boldsymbol{C\!P}\!$ violation in Higgs-gauge interactions: from tabletop experiments to the LHC
Authors:
Vincenzo Cirigliano,
Andreas Crivellin,
Wouter Dekens,
Jordy de Vries,
Martin Hoferichter,
Emanuele Mereghetti
Abstract:
We investigate the interplay between the high- and low-energy phenomenology of $C\!P$-violating interactions of the Higgs boson with gauge bosons. For this purpose we use an effective field theory approach and consider all dimension-6 operators arising in so-called universal theories. We compute their loop-induced contributions to electric dipole moments and the $C\!P$ asymmetry in $B\to X_sγ$, an…
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We investigate the interplay between the high- and low-energy phenomenology of $C\!P$-violating interactions of the Higgs boson with gauge bosons. For this purpose we use an effective field theory approach and consider all dimension-6 operators arising in so-called universal theories. We compute their loop-induced contributions to electric dipole moments and the $C\!P$ asymmetry in $B\to X_sγ$, and compare the resulting current and prospective constraints to the projected sensitivity of the LHC. Low-energy measurements are shown to generally have a far stronger constraining power, which results in highly correlated allowed regions in coupling space, a distinctive pattern that could be probed at the high-luminosity LHC.
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Submitted 29 July, 2019; v1 submitted 8 March, 2019;
originally announced March 2019.
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Lattice QCD and nuclear physics for searches of physics beyond the Standard Model
Authors:
Emanuele Mereghetti
Abstract:
Low-energy tests of fundamental symmetries are extremely sensitive probes of physics beyond the Standard Model, reaching scales that are comparable, if not higher, than directly accessible at the energy frontier. The interpretation of low-energy precision experiments and their connection with models of physics beyond the Standard Model relies on controlling the theoretical uncertainties induced by…
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Low-energy tests of fundamental symmetries are extremely sensitive probes of physics beyond the Standard Model, reaching scales that are comparable, if not higher, than directly accessible at the energy frontier. The interpretation of low-energy precision experiments and their connection with models of physics beyond the Standard Model relies on controlling the theoretical uncertainties induced by the nonperturbative nature of QCD at low energy and of the nuclear interactions. In these proceedings, I will discuss how the interplay of Lattice QCD and nuclear Effective Field Theories can lead to improved predictions for low-energy experiments, with controlled uncertainties. I will describe the framework of chiral Effective Field Theory, and then discuss a few examples, including non-standard $β$ decays, neutrinoless double beta decay and searches for electric dipole moments, to highlight the progress achieved in recent years, and the role that Lattice QCD will play in addressing the remaining open problems.
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Submitted 28 December, 2018;
originally announced December 2018.
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Electric dipole moments: a theory overview
Authors:
Emanuele Mereghetti
Abstract:
Electric dipole moments are extremely sensitive probes of physics beyond the Standard Model. A vibrant experimental program is in place, with the goal of improving existing bounds on the electron and neutron electric dipole moments by one or two orders of magnitude, while testing new ideas for the measurement of electric dipole moments of light ions, such as the proton and the deuteron, at a compa…
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Electric dipole moments are extremely sensitive probes of physics beyond the Standard Model. A vibrant experimental program is in place, with the goal of improving existing bounds on the electron and neutron electric dipole moments by one or two orders of magnitude, while testing new ideas for the measurement of electric dipole moments of light ions, such as the proton and the deuteron, at a comparable level. The success of this program, and its implications for physics beyond the Standard Model, relies on the precise calculation of the electric dipole moments in terms of the couplings of CP-violating operators induced by beyond-the-Standard-Model physics. In light of the nonperturbative nature of both QCD at low energy and of the nuclear interactions, these calculations have proven difficult, and are affected by large theoretical uncertainties. In this talk I will review the progress that has been achieved on different aspects of the calculation of hadronic and nuclear EDMs, the challenges that remain to be faced, and the implications for our understanding of physics beyond the Standard Model.
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Submitted 2 October, 2018;
originally announced October 2018.