Showing 1–10 of 10 results for author: Filandri, E

The ${}^9$Be photodisintegration cross section within Cluster Effective Field Theory

Authors: Ylenia Capitani, Elena Filandri, Chen Ji, Winfried Leidemann, Giuseppina Orlandini

Abstract: A low-energy calculation of ${}^9$Be photodisintegration cross section is presented within an $ααn$ cluster approach. The $αn$ and $αα$ contact interactions are derived from cluster effective field theory. The two-body potentials defined in momentum space are regularized by a Gaussian cutoff. The associated low-energy constants are found by comparing the calculated low-energy T-matrix with its eff… ▽ More A low-energy calculation of ${}^9$Be photodisintegration cross section is presented within an $ααn$ cluster approach. The $αn$ and $αα$ contact interactions are derived from cluster effective field theory. The two-body potentials defined in momentum space are regularized by a Gaussian cutoff. The associated low-energy constants are found by comparing the calculated low-energy T-matrix with its effective range expansion. A three-body state-dependent potential is also introduced in the model. First, the ${}^9$Be three-body binding energy is studied within the non-symmetrized hyperspherical harmonics method. Then, the low-energy cross section is calculated via the Lorentz integral transform method, focussing on the dominant electric dipole transitions. A twofold evaluation of the nuclear current matrix element is presented, employing both the electric dipole transition operator (Siegert theorem) and the one-body convection current operator. This approach is adopted to allow for a discussion of the effect of the many-body currents. △ Less

Submitted 5 June, 2025; originally announced June 2025.

Comments: 16 pages, 16 figures

The 3-$α$ and 4-$α$ particle systems within short-range Effective Field Theory

Authors: E. Filandri, M. Viviani, L. Girlanda, A. Kievsky, L. E. Marcucci

Abstract: ${}^{12}{\rm C}$ and ${}^{16}{\rm O}$ nuclei represent essential elements for life on Earth. The study of their formation plays a key role in understanding heavy element nucleosynthesis and stellar evolution. In this paper we present the study of ${}^{12}{\rm C}$ and ${}^{16}{\rm O}$ nuclei as systems composed of $α… ▽ More ${}^{12}{\rm C}$ and ${}^{16}{\rm O}$ nuclei represent essential elements for life on Earth. The study of their formation plays a key role in understanding heavy element nucleosynthesis and stellar evolution. In this paper we present the study of ${}^{12}{\rm C}$ and ${}^{16}{\rm O}$ nuclei as systems composed of $α$-particle clusters using the short-range effective field theory approach. The fundamental and excited states of the studied nuclei are calculated within an ab-initio approach, using the Hyperspherical Harmonics method. Thanks to the two-body potential and fine-tuning of the three-body force, we have found the ${}^{12}{\rm C}$ system nicely reproduced by theory. However, for the ${}^{16}{\rm O}$ case, it is necessary to include a 4-body force in order to achieve agreement with the experimental data. △ Less

Submitted 24 January, 2025; originally announced January 2025.

The X17 boson and the d(p,e+ e-)3He and d(n,e+ e-)3H processes: a theoretical analysis

Authors: M. Viviani, E. Filandri, L. Girlanda, C. Gustavino, A. Kievsky, L. E. Marcucci

Abstract: The present work deals with the e+ e- pair production in the d(p,e+e-)3He and d(n,e+ e-)3H processes, in order to evidentiate possible effects due to the exchange of a hypothetical low-mass boson, the so-called X17. These processes are studied for energies of the incident beams in the range 18-30 MeV, in order to have a sufficient energy to produce such a boson, whose mass is estimated to be aroun… ▽ More The present work deals with the e+ e- pair production in the d(p,e+e-)3He and d(n,e+ e-)3H processes, in order to evidentiate possible effects due to the exchange of a hypothetical low-mass boson, the so-called X17. These processes are studied for energies of the incident beams in the range 18-30 MeV, in order to have a sufficient energy to produce such a boson, whose mass is estimated to be around 17 MeV. We first analyze them as a purely electromagnetic processes, in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory chiEFT. Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross sections for such processes. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The main aim of the study is to exploit the specular structure of the 3He and 3H nuclei to investigate the isospin dependency of the X17-nucleon interaction, as the alleged "proto-phobicity". △ Less

Submitted 15 April, 2025; v1 submitted 29 August, 2024; originally announced August 2024.

Comments: 19 pages, 15 figures, new version with more details, added two appendices. arXiv admin note: text overlap with arXiv:2104.07808

Journal ref: Phys. Rev. C 111, 034002 (2025)

Momentum dependent nucleon-nucleon contact interactions and their effect on p-d scattering observables

Authors: E. Filandri, L. Girlanda, A. Kievsky, L. E. Marcucci, M. Viviani

Abstract: Starting from a complete set of relativistic nucleon-nucleon contact operators up to order $O(p^4)$ of the expansion in the soft (relative or nucleon) momentum $p$, we show that non-relativistic expansions of relativistic operators involve twenty-six independent combinations, two starting at $O(p^0)$, seven at order $O(p^2)$ and seventeen at order $O(p^4)$. This demonstrates the existence of two l… ▽ More Starting from a complete set of relativistic nucleon-nucleon contact operators up to order $O(p^4)$ of the expansion in the soft (relative or nucleon) momentum $p$, we show that non-relativistic expansions of relativistic operators involve twenty-six independent combinations, two starting at $O(p^0)$, seven at order $O(p^2)$ and seventeen at order $O(p^4)$. This demonstrates the existence of two low-energy free constants that parameterize interactions dependent on the total momentum of the pair of nucleons $P$. The latter, through the use of a unitary transformation, can be removed in the two-nucleon fourth-order contact interaction of the Chiral Effective Field Theory, generating a three-nucleon interaction at the same order. Within a hybrid approach in which this interaction is considered together with the phenomenological potential AV18, we show that the LECs involved can be used to fit very accurate data on the polarization observables of the low-energy $p-d$ scattering, in particular the $A_y$ asymmetry. △ Less

Submitted 17 April, 2024; originally announced April 2024.

Comments: arXiv admin note: text overlap with arXiv:2302.03468

Dark matter scattering off ${}^2$H and ${}^4$He nuclei within chiral effective field theory

Authors: E. Filandri, M. Viviani

Abstract: We study dark matter, assumed to be composed by weak interacting massive particles (WIMPs), scattering off ${}^2$H and ${}^4$He nuclei. In order to parameterize the WIMP-nucleon interaction the chiral effective field theory approach is used. Considering only interactions invariant under parity, charge conjugation and time reversal, we examine five interaction types: scalar, pseudoscalar, vector, a… ▽ More We study dark matter, assumed to be composed by weak interacting massive particles (WIMPs), scattering off ${}^2$H and ${}^4$He nuclei. In order to parameterize the WIMP-nucleon interaction the chiral effective field theory approach is used. Considering only interactions invariant under parity, charge conjugation and time reversal, we examine five interaction types: scalar, pseudoscalar, vector, axial and tensor. Scattering amplitudes between two nucleons and a WIMP are determined up to second order of chiral perturbation theory. We apply this program to calculate the interaction rate as function of the WIMP mass and of the magnitude of the WIMP-quark coupling constants. From our study, we conclude that the scalar nuclear response functions result much greater than the others due to theirs large combination of low energy constants. We verify that the leading order contributions are dominant in this low energy processes. We also provide an estimate for the background due to atmospheric neutrinos. △ Less

Submitted 25 September, 2024; v1 submitted 11 March, 2024; originally announced March 2024.

Comments: v2) List of main changes: -Revised title - Section III has been completely re-organized, moving old subsections IIIA-F to Appendix A. - The sentence before Eq.(4) has been modified; also Eq.(4) has been modified. - Throghout the paper, the notation C^X_{+-} has been adopted - Appendix A has been added - Old Appendix A has been now renamed Appendix B

Relativistic constraints on 3N contact interactions

Authors: Alessia Nasoni, Elena Filandri, Luca Girlanda

Abstract: In this paper we analyze the relativistic corrections to the leading order three-nucleon (3N) contact interactions. These boost corrections are derived first from the nonrelativistic reduction of covariant Lagrangians and later from the Poincaré algebra constraints on nonrelativistic theories. We show that in order to describe the 3N potential in reference frames other than the center-of-mass fram… ▽ More In this paper we analyze the relativistic corrections to the leading order three-nucleon (3N) contact interactions. These boost corrections are derived first from the nonrelativistic reduction of covariant Lagrangians and later from the Poincaré algebra constraints on nonrelativistic theories. We show that in order to describe the 3N potential in reference frames other than the center-of-mass frame, the inclusion of five additional terms with fixed coefficients is required. These terms will be relevant in systems with mass number A>3. How they will affect EFT calculations of binding energies and scattering observables in these systems should be investigated. △ Less

Submitted 25 August, 2023; originally announced August 2023.

Momentum dependent nucleon-nucleon contact interaction from a relativistic Lagrangian

Authors: E. Filandri, L. Girlanda

Abstract: A complete set of parity- and time-reversal conserving relativistic nucleon-nucleon contact operators is identified up to the order $O(p^4)$ of the expansion in soft momenta $p$. A basis is also provided for the corresponding non-relativistic operators contributing in the general reference frame. We show that the non-relativistic expansions of the relativistic operators involve twenty-six independ… ▽ More A complete set of parity- and time-reversal conserving relativistic nucleon-nucleon contact operators is identified up to the order $O(p^4)$ of the expansion in soft momenta $p$. A basis is also provided for the corresponding non-relativistic operators contributing in the general reference frame. We show that the non-relativistic expansions of the relativistic operators involve twenty-six independent combinations, two starting at $O(p^0)$, seven at order $O(p^2)$ and seventeen at order $O(p^4)$. This gives supporting evidence to the existence of two free low-energy constants which parametrize an interaction depending on the total nucleon pair momentum ${\bf P}$, and were recently found to be instrumental for the resolution of the long standing $A_y$ problem in low-energy $p-d$ scattering. Furthermore, all remaining ${\bf P}$-dependent interactions at the same order are uniquely determined as relativistic corrections. △ Less

Submitted 9 May, 2023; v1 submitted 17 March, 2023; originally announced March 2023.

Comments: Minor changes, added references, to appear in Physics Letters B

Journal ref: Physics Letters B 841 (2023) 137957

Effect of the N3LO three-nucleon contact interaction on p-d scattering observables

Authors: L. Girlanda, E. Filandri, A. Kievsky, L. E. Marcucci, M. Viviani

Abstract: A unitary transformation allows to remove redundant terms in the two-nucleon (2N) contact interaction at the fourth order (N3LO) in the low-energy expansion of Chiral Effective Field Theory. In so doing a three-nucleon (3N) interaction is generated. We express its short-range component in terms of five combinations of low-energy constants (LECs) parametrizing the N3LO 2N contact Lagrangian. Within… ▽ More A unitary transformation allows to remove redundant terms in the two-nucleon (2N) contact interaction at the fourth order (N3LO) in the low-energy expansion of Chiral Effective Field Theory. In so doing a three-nucleon (3N) interaction is generated. We express its short-range component in terms of five combinations of low-energy constants (LECs) parametrizing the N3LO 2N contact Lagrangian. Within a hybrid approach, in which this interaction is considered in conjunction with the phenomenological AV18 2N potential, we show that the involved LECs can be used to fit very accurate data on polarization observables of low-energy $p-d$ scattering, in particular the $A_y$ asymmetry. The resulting interaction is of the right order of magnitude for a N3LO contribution. △ Less

Submitted 7 February, 2023; originally announced February 2023.

Comments: 9 pages, 2 figures

The X17 boson and the $^3$H$(p,e^+ e^-)^4$He and $^3$He$(n,e^+ e^-)^4$He processes: a theoretical analysis

Authors: M. Viviani, E. Filandri, L. Girlanda, C. Gustavino, A. Kievsky, L. E. Marcucci, R. Schiavilla

Abstract: The present work deals with $e^+$-$e^-$ pair production in the four-nucleon system. We first analyze the process as a purely electromagnetic one in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory ($χ$EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact… ▽ More The present work deals with $e^+$-$e^-$ pair production in the four-nucleon system. We first analyze the process as a purely electromagnetic one in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory ($χ$EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross section for such a process. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The ab initio calculations use exact hyperspherical-harmonics methods to describe the bound state and low-energy spectrum of the $A\,$=$\,4$ continuum, and fully account for initial state interaction effects in the $3+1$ clusters. While electromagnetic interactions are treated to high orders in the chiral expansion, the interactions of the hypothetical boson with nucleons are modeled in leading-order $χ$EFT (albeit, in some instances, selected subleading contributions are also accounted for). We also provide an overview of possible future experiments probing pair production in the $A\,$=$\,4$ system at a number of candidate facilities.facilities. △ Less

Submitted 18 June, 2021; v1 submitted 15 April, 2021; originally announced April 2021.

Comments: 32 pages, 17 figures. Corrected version, having fixed a problem with a phase in the multipolar expansions. Only Figs. 4 and 10 change significantly, the rest only marginally. The conclusions are unchanged. We include also a number of improvements: 1) better wave functions, 2) the isoscalar pseudoscalar case, and 3) the comparison with the new ATOMKI data (see new Fig. 17)

Beryllium-9 in Cluster Effective Field Theory

Authors: Elena Filandri, Paolo Andreatta, Carlo A. Manzata, Chen Ji, W. Leidemann, G. Orlandini

Abstract: We study the 9 Be ground-state energy with non-local $α-$n and $α-α$ potentials derived from Cluster Effective Field Theory. The short-distance dependence of the interaction is regulated with a momentum cutoff. The potential parameters are fitted to reproduce the scattering length and effective range. We implement such potential models in a Non-Symmetrized Hyperspherical Harmonics (NSHH) code in m… ▽ More We study the 9 Be ground-state energy with non-local $α-$n and $α-α$ potentials derived from Cluster Effective Field Theory. The short-distance dependence of the interaction is regulated with a momentum cutoff. The potential parameters are fitted to reproduce the scattering length and effective range. We implement such potential models in a Non-Symmetrized Hyperspherical Harmonics (NSHH) code in momentum space. In addition we calculate ground state energies of various alpha nuclei. Work is in progress on a calculation of the photodisintegration of 9Be with the Lorentz Integral Transform (LIT) method. △ Less

Submitted 3 February, 2020; originally announced February 2020.