Showing 1–50 of 218 results for author: Strickland, M

Bottomonium suppression in pNRQCD and open quantum system approach

Authors: Ajaharul Islam, Nora Brambilla, Miguel Ángel Escobedo, Michael Strickland, Antonio Vairo, Peter Vander Griend

Abstract: By employing the potential non-relativistic quantum chromodynamics (pNRQCD) effective field theory within an open quantum system framework, we derive a Lindblad equation governing the evolution of the heavy-quarkonium reduced density matrix, accurate to next-to-leading order (NLO) in the ratio of the state's binding energy to the medium's temperature [1]. The derived NLO Lindblad equation provides… ▽ More By employing the potential non-relativistic quantum chromodynamics (pNRQCD) effective field theory within an open quantum system framework, we derive a Lindblad equation governing the evolution of the heavy-quarkonium reduced density matrix, accurate to next-to-leading order (NLO) in the ratio of the state's binding energy to the medium's temperature [1]. The derived NLO Lindblad equation provides a more reliable description of heavy-quarkonium evolution in the quark-gluon plasma at low temperatures compared to the leading-order truncation. For phenomenological applications, we numerically solve this equation using the quantum trajectories algorithm. By averaging over Monte Carlo-sampled quantum jumps, we obtain solutions without truncation in the angular momentum quantum number of the considered states. Our analysis highlights the importance of quantum jumps in the nonequilibrium evolution of bottomonium states within the quark-gluon plasma [2]. Additionally, we demonstrate that the quantum regeneration of singlet states from octet configurations is essential to explain experimental observations of bottomonium suppression. The heavy-quarkonium transport coefficients used in our study align with recent lattice QCD determinations. △ Less

Submitted 28 March, 2025; originally announced March 2025.

Comments: 12 Pages, 5 figures, Contribution to the proceedings of the "Confinement XVI"

Efficient simulation of quarkonium master equation beyond the dipole approximation

Authors: Jorge M. Mtz-Vera, Andrea Beraudo, Miguel Ángel Escobedo, Paolo Parotto, Michael Strickland

Abstract: QTRAJ is a computer code that simulates the propagation of quarkonium in the quark-gluon plasma (QGP) based on the quantum-trajectory algorithm. This algorithm solves a master equation in which the quarkonium is treated as an open quantum system (OQS). A major advantage of this approach is that it turns a 3D spatial evolution for a density matrix into a 1D Schrödinger equation for a wavefunction w… ▽ More QTRAJ is a computer code that simulates the propagation of quarkonium in the quark-gluon plasma (QGP) based on the quantum-trajectory algorithm. This algorithm solves a master equation in which the quarkonium is treated as an open quantum system (OQS). A major advantage of this approach is that it turns a 3D spatial evolution for a density matrix into a 1D Schrödinger equation for a wavefunction with a non-hermitian Hamiltonian, drastically reducing the computational cost. So far, the interaction implemented in the master equation was obtained within the framework of potential non-relativistic QCD (pNRQCD), and restricted to the regime $rT \ll 1$, where $r$ is the size of the color dipole and $T$ is the temperature. In the environment produced in heavy-ion collisions (HIC's) this limit is accurate for $Υ(1S)$, but the applicability to other quarkonium states is dubious. In the present study we generalize the above approach, extending it to the regime $rT\!\sim\! 1$ in the one-gluon exchange approximation, with proper Hard Thermal Loop (HTL) resummation of medium effects. This is done by implementing new jump operators connecting different color states of the $Q\bar Q$ pair and expanding them in plane waves, giving rise to a variation of the algorithm present in QTRAJ 1.0. Here we provide an overview of this approach comparing the $rT \ll 1$ and $rT\sim 1$ cases, and we discuss prospects for phenomenological application to excited states of bottomonium. △ Less

Submitted 24 October, 2024; originally announced October 2024.

Comments: Proceedings of the Conference QNP 2024

Far-from-equilibrium attractors in kinetic theory with two different relaxation times

Authors: Ferdinando Frascà, Andrea Beraudo, Michael Strickland

Abstract: We solve a Boltzmann equation for massless quark and gluon fluids in a transversally homogeneous, longitudinally boost-invariant expansion. Quarks can be out of chemical equilibrium and the relaxation times of the two species are assumed to be connected by Casimir scaling. We numerically calculate moments of the distribution functions, identifying their early- and late-time attractors and reconstr… ▽ More We solve a Boltzmann equation for massless quark and gluon fluids in a transversally homogeneous, longitudinally boost-invariant expansion. Quarks can be out of chemical equilibrium and the relaxation times of the two species are assumed to be connected by Casimir scaling. We numerically calculate moments of the distribution functions, identifying their early- and late-time attractors and reconstructing also the full distributions. These attractors appear when the system is still far from local thermalization, before hydrodynamics traditionally would be expected to apply. We also analyze the evolution of entropy production for different initial momentum anisotropies and quark abundances. △ Less

Submitted 19 December, 2024; v1 submitted 24 October, 2024; originally announced October 2024.

Comments: Proceeedings of the 10th International Conference on Quarks and Nuclear Physics (QNP2024)

Far-from-equilibrium attractors in kinetic theory for a mixture of quark and gluon fluids

Authors: Ferdinando Frascà, Andrea Beraudo, Michael Strickland

Abstract: We exactly solve an RTA-Boltzmann equation that describes the dynamics of coupled massless quark and gluon fluids undergoing transversally homogeneous longitudinal boost-invariant expansion. We include a fugacity parameter that allows quarks to be out of chemical equilibrium and we account for the different collision rates of quarks and gluons, which are related by Casimir scaling. Based on these… ▽ More We exactly solve an RTA-Boltzmann equation that describes the dynamics of coupled massless quark and gluon fluids undergoing transversally homogeneous longitudinal boost-invariant expansion. We include a fugacity parameter that allows quarks to be out of chemical equilibrium and we account for the different collision rates of quarks and gluons, which are related by Casimir scaling. Based on these assumptions, we numerically determine the evolution of a large set of moments of the quark and gluon distribution functions and reconstruct their entire distribution functions. We find that both late and early-time attractors exist for all moments of the distribution functions containing more than one power of the squared longitudinal momentum. These attractors emerge long before the system reaches the regime where hydrodynamic approximations apply. In addition, we discuss how the shear viscous corrections and entropy density of the fluid mixture evolve and consider the properties of their respective attractors. Finally, the entropy production is also investigated for different initial values of momentum anisotropy and quark abundance. △ Less

Submitted 20 December, 2024; v1 submitted 24 July, 2024; originally announced July 2024.

Bottomonium suppression from the three-loop QCD potential

Authors: Nora Brambilla, Tom Magorsch, Michael Strickland, Antonio Vairo, Peter Vander Griend

Abstract: We compute the suppression of bottomonium in the quark-gluon plasma using the three-loop QCD static potential. The potential describes the spin-averaged bottomonium spectrum below threshold with a less than 1% error. Within potential nonrelativistic quantum chromodynamics and an open quantum systems framework, we compute the evolution of the bottomonium density matrix. The values of the quarkonium… ▽ More We compute the suppression of bottomonium in the quark-gluon plasma using the three-loop QCD static potential. The potential describes the spin-averaged bottomonium spectrum below threshold with a less than 1% error. Within potential nonrelativistic quantum chromodynamics and an open quantum systems framework, we compute the evolution of the bottomonium density matrix. The values of the quarkonium transport coefficients are obtained from lattice QCD measurements of the bottomonium in-medium width and thermal mass shift; we additionally include for the first time a vacuum contribution to the dispersive coefficient $γ$. Using the three-loop potential and the values of the heavy quarkonium transport coefficients, we find that the resulting bottomonium nuclear modification factor is consistent with experimental observations, while at the same time reproducing the lattice measurements of the in-medium width. △ Less

Submitted 22 March, 2024; originally announced March 2024.

Comments: 15 pages, 3 figures, 1 table

Report number: TUM-EFT 186/23; FERMILAB-PUB-24-0029-V

Energy loss of a heavy fermion in a collisional QED plasma

Authors: Yun Guo, Luhua Qiu, Ruizhe Zhao, Michael Strickland

Abstract: We compute the energy loss of heavy fermions moving in a plasma, taking into account the modification of the photon collective modes induced by collisions using a Bhatnagar-Gross-Krook collisional kernel. We include contributions from both hard and soft scatterings of the heavy fermion using a collisionally modified hard-thermal-loop resummed propagator. Using this method, one does not need to int… ▽ More We compute the energy loss of heavy fermions moving in a plasma, taking into account the modification of the photon collective modes induced by collisions using a Bhatnagar-Gross-Krook collisional kernel. We include contributions from both hard and soft scatterings of the heavy fermion using a collisionally modified hard-thermal-loop resummed propagator. Using this method, one does not need to introduce a separation scale between hard- and soft-momentum exchanges. To place our calculation in context, we review other theoretical approaches to computing the collisional energy loss of fermions and discuss the systematics and results obtained in each approach compared to using a resummed propagator for both hard and soft momentum exchanges. Our final results indicate that self-consistently including the effect of collisions in the self-energies of the resummed propagator results in an increased energy loss compared to using collisionless hard-thermal-loop propagators. The effect becomes larger as the magnitude of the coupling constant and the velocity of the fermion increase. △ Less

Submitted 15 June, 2024; v1 submitted 11 March, 2024; originally announced March 2024.

Comments: 25 pages, 7 figures, final version published in PRD

Journal ref: Phys. Rev. D 109, 114025 (2024)

Hydrodynamization and resummed viscous hydrodynamics

Authors: Michael Strickland

Abstract: In this contributed chapter, I review our current understanding of the applicability of hydrodynamics to modeling the quark-gluon plasma (QGP), focusing on the question of hydrodynamization/thermalization of the QGP and the anisotropic hydrodynamics (aHydro) far-from-equilibrium hydrodynamic framework. I discuss the existence of far-from-equilibrium hydrodynamic attractors and methods for determin… ▽ More In this contributed chapter, I review our current understanding of the applicability of hydrodynamics to modeling the quark-gluon plasma (QGP), focusing on the question of hydrodynamization/thermalization of the QGP and the anisotropic hydrodynamics (aHydro) far-from-equilibrium hydrodynamic framework. I discuss the existence of far-from-equilibrium hydrodynamic attractors and methods for determining attractors within different hydrodynamical frameworks. I also discuss the determination of attractors from exact solutions to the Boltzmann equation in relaxation time approximation and effective kinetic field theory applied to quantum chromodynamics. I then present comparisons of the kinetic attractors with the attractors obtained in standard second-viscous hydrodynamics frameworks and anisotropic hydrodynamics. I demonstrate that, due to the resummation of terms to all orders in the inverse Reynolds number, the anisotropic hydrodynamics framework can describe both the weak- and strong-interaction limits. I then review the phenomenological application of anisotropic hydrodynamics to relativistic heavy-ion collisions using both quasiparticle aHydro and second-order viscous aHydro. The phenomenological results indicate that aHydro provides a controlled extension of dissipative relativistic hydrodynamics to the early-time far-from-equilibrium stage of heavy-ion collisions. This allows one to better describe the data and to extract the temperature dependence of transport coefficients at much higher temperatures than linearized second-order viscous hydrodynamics. △ Less

Submitted 14 February, 2024; originally announced February 2024.

Comments: 68 pages, 25 figures; Contributed chapter to Quark-Gluon Plasma 6 book

Comparative Study of Quarkonium Transport in Hot QCD Matter

Authors: A. Andronic, P. B. Gossiaux, P. Petreczky, R. Rapp, M. Strickland, J. P. Blaizot, N. Brambilla, P. Braun-Munzinger, B. Chen, S. Delorme, X. Du, M. A. Escobedo, E. G. Ferreiro, A. Jaiswal, A. Rothkopf, T. Song, J. Stachel, P. Vander Griend, R. Vogt, B. Wu, J. Zhao, X. Yao

Abstract: This document summarizes the efforts of the EMMI Rapid Reaction Task Force on "Suppression and (re)generation of quarkonium in heavy-ion collisions at the LHC", centered around their 2019 and 2022 meetings. It provides a review of existing experimental results and theoretical approaches, including lattice QCD calculations and semiclassical and quantum approaches for the dynamical evolution of quar… ▽ More This document summarizes the efforts of the EMMI Rapid Reaction Task Force on "Suppression and (re)generation of quarkonium in heavy-ion collisions at the LHC", centered around their 2019 and 2022 meetings. It provides a review of existing experimental results and theoretical approaches, including lattice QCD calculations and semiclassical and quantum approaches for the dynamical evolution of quarkonia in the quark-gluon plasma as probed in high-energy heavy-ion collisions. The key ingredients of the transport models are itemized to facilitate comparisons of calculated quantities such as reaction rates, binding energies, and nuclear modification factors. A diagnostic assessment of the various results is attempted and coupled with an outlook for the future. △ Less

Submitted 6 February, 2024; originally announced February 2024.

Comments: 54 pages, 19 figures

Photon-triggered jets as probes of multi-stage jet modification

Authors: C. Sirimanna, Y. Tachibana, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, M. Kordell II, A. Kumar, R. Kunnawalkam-Elayavalli, J. Latessa, S. Lee , et al. (28 additional authors not shown)

Abstract: Prompt photons are created in the early stages of heavy ion collisions and traverse the QGP medium without any interaction. Therefore, photon-triggered jets can be used to study the jet quenching in the QGP medium. In this work, photon-triggered jets are studied through different jet and jet substructure observables for different collision systems and energies using the JETSCAPE framework. Since t… ▽ More Prompt photons are created in the early stages of heavy ion collisions and traverse the QGP medium without any interaction. Therefore, photon-triggered jets can be used to study the jet quenching in the QGP medium. In this work, photon-triggered jets are studied through different jet and jet substructure observables for different collision systems and energies using the JETSCAPE framework. Since the multistage evolution used in the JETSCAPE framework is adequate to describe a wide range of experimental observables simultaneously using the same parameter tune, we use the same parameters tuned for jet and leading hadron studies. The same isolation criteria used in the experimental analysis are used to identify prompt photons for better comparison. For the first time, high-accuracy JETSCAPE results are compared with multi-energy LHC and RHIC measurements to better understand the deviations observed in prior studies. This study highlights the importance of multistage evolution for the simultaneous description of experimental observables through different collision systems and energies using a single parameter tune. △ Less

Submitted 30 January, 2024; originally announced January 2024.

Comments: 4 pages, 5 figures. Proceedings of Quark Matter 2023 - XXXth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions, Houston, TX, 3-9 September 2023

Bottomonium suppression in 5.02 and 8.16 TeV p-Pb collisions

Authors: Michael Strickland, Sabin Thapa, Ramona Vogt

Abstract: We compute the suppression of Upsilon(1S), Upsilon(2S), and Upsilon(3S) states in p-Pb collisions relative to pp collisions, including nuclear parton distribution function (nPDF) effects, coherent energy loss, momentum broadening, and final-state interactions in the quark-gluon plasma. We employ the EPPS21 nPDFs and calculate the uncertainty resulting from variation over the associated error sets.… ▽ More We compute the suppression of Upsilon(1S), Upsilon(2S), and Upsilon(3S) states in p-Pb collisions relative to pp collisions, including nuclear parton distribution function (nPDF) effects, coherent energy loss, momentum broadening, and final-state interactions in the quark-gluon plasma. We employ the EPPS21 nPDFs and calculate the uncertainty resulting from variation over the associated error sets. To compute coherent energy loss and momentum broadening, we follow the approach of Arleo, Peigne, and collaborators. The 3+1D viscous hydrodynamical background evolution of the quark-gluon plasma is generated by anisotropic hydrodynamics. The in-medium suppression of bottomonium in the quark-gluon plasma is computed using a next-to-leading-order open quantum system framework formulated within potential nonrelativistic quantum chromodynamics. We find that inclusion of all these effects provides a reasonable description of experimental data from the ALICE, ATLAS, CMS, and LHCb collaborations for the suppression of Upsilon(1S), Upsilon(2S), and Upsilon(3S) as a function of both transverse momentum and rapidity. △ Less

Submitted 29 January, 2024; originally announced January 2024.

Comments: 20 pages, 12 figures; Ancillary files contain data corresponding to figures 6-12

Measuring jet quenching with a Bayesian inference analysis of hadron and jet data by JETSCAPE

Authors: R. Ehlers, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, L. Du, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, M. Kordell II, A. Kumar, R. Kunnawalkam-Elayavalli, J. Latessa, S. Lee, Y. -J. Lee, D. Liyanage , et al. (28 additional authors not shown)

Abstract: The JETSCAPE Collaboration reports the first multi-messenger study of the QGP jet transport parameter $\hat{q}$ using Bayesian inference, incorporating all available hadron and jet inclusive yield and jet substructure data from RHIC and the LHC. The theoretical model utilizes virtuality-dependent in-medium partonic energy loss coupled to a detailed dynamical model of QGP evolution. Tension is obse… ▽ More The JETSCAPE Collaboration reports the first multi-messenger study of the QGP jet transport parameter $\hat{q}$ using Bayesian inference, incorporating all available hadron and jet inclusive yield and jet substructure data from RHIC and the LHC. The theoretical model utilizes virtuality-dependent in-medium partonic energy loss coupled to a detailed dynamical model of QGP evolution. Tension is observed when constraining $\hat{q}$ for different kinematic cuts of the inclusive hadron data. The addition of substructure data is shown to improve the constraint on $\hat{q}$, without inducing tension with the constraint due to inclusive observables. These studies provide new insight into the mechanisms of jet interactions in matter, and point to next steps in the field for comprehensive understanding of jet quenching as a probe of the QGP. △ Less

Submitted 8 January, 2024; originally announced January 2024.

Comments: 4 pages, 2 figures. Proceedings of Quark Matter 2023 - XXXth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions, Houston, TX, 3-9 September 2023

3D Multi-system Bayesian Calibration with Energy Conservation to Study Rapidity-dependent Dynamics of Nuclear Collisions

Authors: Andi Mankolli, Aaron Angerami, Ritu Arora, Steffen Bass, Shanshan Cao, Yi Chen, Lipei Du, Raymond Ehlers, Hannah Elfner, Wenkai Fan, Rainer J. Fries, Charles Gale, Yayun He, Ulrich Heinz, Barbara Jacak, Peter Jacobs, Sangyong Jeon, Yi Ji, Lauren Kasper, Michael Kordell II, Amit Kumar, R. Kunnawalkam-Elayavalli, Joseph Latessa, Sook H. Lee, Yen-Jie Lee , et al. (26 additional authors not shown)

Abstract: Considerable information about the early-stage dynamics of heavy-ion collisions is encoded in the rapidity dependence of measurements. To leverage the large amount of experimental data, we perform a systematic analysis using three-dimensional hydrodynamic simulations of multiple collision systems -- large and small, symmetric and asymmetric. Specifically, we perform fully 3D multi-stage hydrodynam… ▽ More Considerable information about the early-stage dynamics of heavy-ion collisions is encoded in the rapidity dependence of measurements. To leverage the large amount of experimental data, we perform a systematic analysis using three-dimensional hydrodynamic simulations of multiple collision systems -- large and small, symmetric and asymmetric. Specifically, we perform fully 3D multi-stage hydrodynamic simulations initialized by a parameterized model for rapidity-dependent energy deposition, which we calibrate on the hadron multiplicity and anisotropic flow coefficients. We utilize Bayesian inference to constrain properties of the early- and late- time dynamics of the system, and highlight the impact of enforcing global energy conservation in our 3D model. △ Less

Submitted 31 December, 2023; originally announced January 2024.

Far-from-equilibrium attractors for massive kinetic theory in the relaxation time approximation

Authors: Huda Alalawi, Michael Strickland

Abstract: In this proceedings contribution, we summarize recent findings concerning the presence of early- and late-time attractors in non-conformal kinetic theory. We study the effects of varying both the initial momentum-space anisotropy and initialization times using an exact solution of the 0+1D boost-invariant Boltzmann equation with a mass- and temperature-dependent relaxation time. Our findings suppo… ▽ More In this proceedings contribution, we summarize recent findings concerning the presence of early- and late-time attractors in non-conformal kinetic theory. We study the effects of varying both the initial momentum-space anisotropy and initialization times using an exact solution of the 0+1D boost-invariant Boltzmann equation with a mass- and temperature-dependent relaxation time. Our findings support the existence of a longitudinal pressure attractor, but they do not support the existence of distinct attractors for the bulk viscous and shear pressures. Considering a large set of integral moments, we show that for moments with greater than one power of longitudinal momentum squared, both early- and late-time attractors are present. △ Less

Submitted 4 December, 2023; originally announced December 2023.

Comments: 4 pages, 2figures; Proceedings contribution to Quark Matter 2023, September 3-9 2023, Houston, Texas, USA

Hybrid Hadronization of Jet Showers from $e^++e^-$ to $A+A$ with JETSCAPE

Authors: Cameron Parker, Aaron Angerami, Ritu Arora, Steffen Bass, Shanshan Cao, Yi Chen, Raymond Ehlers, Hannah Elfner, Wenkai Fan, Rainer J. Fries, Charles Gale, Yayun He, Ulrich Heinz, Barbara Jacak, Peter Jacobs, Sangyong Jeon, Yi Ji, Lauren Kasper, Michael Kordell II, Amit Kumar, Joseph Latessa, Yen-Jie Lee, Roy Lemmon, Dananjaya Liyanage, Arthur Lopez , et al. (26 additional authors not shown)

Abstract: In this talk we review jet production in a large variety of collision systems using the JETSCAPE event generator and Hybrid Hadronization. Hybrid Hadronization combines quark recombination, applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems. It can therefore smoothly describe the transition from very dilute parton syst… ▽ More In this talk we review jet production in a large variety of collision systems using the JETSCAPE event generator and Hybrid Hadronization. Hybrid Hadronization combines quark recombination, applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems. It can therefore smoothly describe the transition from very dilute parton systems like $e^++e^-$ to full $A+A$ collisions. We test this picture by using JETSCAPE to generate jets in various systems. Comparison to experimental data in $e^++e^-$ and $p+p$ collisions allows for a precise tuning of vacuum baseline parameters in JETSCAPE and Hybrid Hadronization. Proceeding to systems with jets embedded in a medium, we study in-medium hadronization for jet showers. We quantify the effects of an ambient medium, focusing in particular on the dependence on the collective flow and size of the medium. Our results clarify the effects we expect from in-medium hadronization of jets on observables like fragmentation functions, hadron chemistry and jet shape. △ Less

Submitted 7 November, 2023; v1 submitted 31 October, 2023; originally announced October 2023.

Comments: 6 pages, 4 figures, Hard Probes 2023 conference, accepted for publication in Proceedings of Science: version 2, references added, typos fixed

A multistage framework for studying the evolution of jets and high-$p_T$ probes in small collision systems

Authors: Abhijit Majumder, Aaron Angerami, Ritu Arora, Steffen Bass, Shanshan Cao, Yi Chen, Raymond Ehlers, Hannah Elfner, Wenkai Fan, Rainer J. Fries, Charles Gale, Yayun He, Ulrich Heinz, Barbara Jacak, Peter Jacobs, Sangyong Jeon, Yi Ji, Lauren Kasper, Michael Kordell II, Amit Kumar, Joseph Latessa, Yen-Jie Lee, Roy Lemmon, Dananjaya Liyanage, Arthur Lopez , et al. (26 additional authors not shown)

Abstract: Understanding the modification of jets and high-$p_T$ probes in small systems requires the integration of soft and hard physics. We present recent developments in extending the JETSCAPE framework to build an event generator, which includes correlations between soft and hard partons, to study jet observables in small systems. The multi-scale physics of the collision is separated into different stag… ▽ More Understanding the modification of jets and high-$p_T$ probes in small systems requires the integration of soft and hard physics. We present recent developments in extending the JETSCAPE framework to build an event generator, which includes correlations between soft and hard partons, to study jet observables in small systems. The multi-scale physics of the collision is separated into different stages. Hard scatterings are first sampled at binary collision positions provided by the Glauber geometry. They are then propagated backward in space-time following an initial-state shower to obtain the initiating partons' energies and momenta before the collision. These energies and momenta are then subtracted from the incoming colliding nucleons for soft-particle production, modeled by the 3D-Glauber + hydrodynamics + hadronic transport framework. This new hybrid approach (X-SCAPE) includes non-trivial correlations between jet and soft particle productions in small systems. We calibrate this framework with the final state hadrons' $p_T$-spectra from low to high $p_T$ in $p$-$p$, and and then compare with the spectra in $p$-$Pb$ collisions from the LHC. We also present results for additional observables such as the distributions of event activity as a function of the hardest jet $p_T$ in forward and mid-rapidity for both $p$-$p$ and $p$-$Pb$ collisions. △ Less

Submitted 1 November, 2023; v1 submitted 4 August, 2023; originally announced August 2023.

Comments: 6 pages, 6 figures, Proceedings of Hard Probes 2023, 26-31 March 2023 Aschaffenburg, Germany

Journal ref: Proceedings of Science (Hard Probes 2023) 2023

A new metric improving Bayesian calibration of a multistage approach studying hadron and inclusive jet suppression

Authors: W. Fan, G. Vujanovic, S. A. Bass, A. Angerami, R. Arora, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, M. Kordell II, A. Kumar, J. Latessa, Y. -J. Lee , et al. (30 additional authors not shown)

Abstract: We study parton energy-momentum exchange with the quark gluon plasma (QGP) within a multistage approach composed of in-medium DGLAP evolution at high virtuality, and (linearized) Boltzmann Transport formalism at lower virtuality. This multistage simulation is then calibrated in comparison with high $p_T$ charged hadrons, D-mesons, and the inclusive jet nuclear modification factors, using Bayesian… ▽ More We study parton energy-momentum exchange with the quark gluon plasma (QGP) within a multistage approach composed of in-medium DGLAP evolution at high virtuality, and (linearized) Boltzmann Transport formalism at lower virtuality. This multistage simulation is then calibrated in comparison with high $p_T$ charged hadrons, D-mesons, and the inclusive jet nuclear modification factors, using Bayesian model-to-data comparison, to extract the virtuality-dependent transverse momentum broadening transport coefficient $\hat{q}$. To facilitate this undertaking, we develop a quantitative metric for validating the Bayesian workflow, which is used to analyze the sensitivity of various model parameters to individual observables. The usefulness of this new metric in improving Bayesian model emulation is shown to be highly beneficial for future such analyses. △ Less

Submitted 27 October, 2023; v1 submitted 18 July, 2023; originally announced July 2023.

Comments: 24 pages, 16 figures

Multiscale evolution of heavy flavor in the QGP

Authors: G. Vujanovic, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, M. Kordell II, A. Kumar, J. Latessa, Y. -J. Lee , et al. (30 additional authors not shown)

Abstract: Shower development dynamics for a jet traveling through the quark-gluon plasma (QGP) is a multiscale process, where the heavy flavor mass is an important scale. During the high virtuality portion of the jet evolution in the QGP, emission of gluons from a heavy flavor is modified owing to heavy quark mass. Medium-induced radiation of heavy flavor is sensitive to microscopic processes (e.g. diffusio… ▽ More Shower development dynamics for a jet traveling through the quark-gluon plasma (QGP) is a multiscale process, where the heavy flavor mass is an important scale. During the high virtuality portion of the jet evolution in the QGP, emission of gluons from a heavy flavor is modified owing to heavy quark mass. Medium-induced radiation of heavy flavor is sensitive to microscopic processes (e.g. diffusion), whose virtuality dependence is phenomenologically explored in this study. In the lower virtuality part of shower evolution, i.e. when the mass is comparable to the virtuality of the parton, scattering and radiation processes of heavy quarks differ from light quarks. The effects of these mechanisms on shower development in heavy flavor tagged showers in the QGP is explored here. Furthermore, this multiscale study examines dynamical pair production of heavy flavor (via virtual gluon splittings) and their subsequent evolution in the QGP, which is not possible otherwise. A realistic event-by-event simulation is performed using the JETSCAPE framework. Energy-momentum exchange with the medium proceeds using a weak coupling recoil approach. Using leading hadron and open heavy flavor observables, differences in heavy versus light quark energy-loss mechanisms are explored, while the importance of heavy flavor pair production is highlighted along with future directions to study. △ Less

Submitted 27 October, 2023; v1 submitted 18 July, 2023; originally announced July 2023.

Comments: 6 pages, 3 figures, contribution to the Hard Probes 2023 proceedings

Effects of multi-scale jet-medium interactions on jet substructures

Authors: JETSCAPE Collaboration, Y. Tachibana, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, K. Kauder, L. Kasper, W. Ke, M. Kelsey , et al. (35 additional authors not shown)

Abstract: We utilize event-by-event Monte Carlo simulations within the JETSCAPE framework to examine scale-dependent jet-medium interactions in heavy-ion collisions. The reduction in jet-medium interaction during the early high-virtuality stage, where the medium is resolved at a short distance scale, is emphasized as a key element in explaining multiple jet observables, particularly substructures, simultane… ▽ More We utilize event-by-event Monte Carlo simulations within the JETSCAPE framework to examine scale-dependent jet-medium interactions in heavy-ion collisions. The reduction in jet-medium interaction during the early high-virtuality stage, where the medium is resolved at a short distance scale, is emphasized as a key element in explaining multiple jet observables, particularly substructures, simultaneously. By employing the MATTER+LBT setup, which incorporates this explicit reduction of medium effects at high virtuality, we investigate jet substructure observables, such as Soft Drop groomed observables. When contrasted with existing data, our findings spotlight the significant influence of the reduction at the early high-virtuality stages. Furthermore, we study the substructure of gamma-tagged jets, providing predictive insights for future experimental analyses. This broadens our understanding of the various contributing factors involved in modifying jet substructures. △ Less

Submitted 16 July, 2023; originally announced July 2023.

Comments: 6 pages, 4 figures, contribution to the Hard Probes 2023 proceedings

Transverse momentum dependent feed-down fractions for bottomonium production

Authors: Jacob Boyd, Sabin Thapa, Michael Strickland

Abstract: We extract transverse momentum dependent feed-down fractions for bottomonium production using a data-driven approach. We use data published by the ATLAS, CMS, and LHCb Collaborations for sqrt(s) = 7 TeV proton-proton collisions. Based on this collected data, we produce fits to the differential cross sections for the production of both S- and P-wave bottomonium states. Combining these fits with bra… ▽ More We extract transverse momentum dependent feed-down fractions for bottomonium production using a data-driven approach. We use data published by the ATLAS, CMS, and LHCb Collaborations for sqrt(s) = 7 TeV proton-proton collisions. Based on this collected data, we produce fits to the differential cross sections for the production of both S- and P-wave bottomonium states. Combining these fits with branching ratios for excited state decays from the Particle Data Group, we compute the feed-down fractions for both the Upsilon(1S) and Upsilon(2S) as a function of transverse momentum. Our results indicate a strong dependence on transverse momentum, which is consistent with prior extractions of the feed-down fractions. When evaluated at the average momentum of the states, we find that approximately 75% of Upsilon(1S) and Upsilon(2S) states are produced directly. Our results for the transverse momentum dependent feed-down fractions are provided in tabulated form so that they can be used by other research groups. △ Less

Submitted 18 November, 2023; v1 submitted 7 July, 2023; originally announced July 2023.

Comments: 10 pages, 6 figures, 5 tables, and associated data files; v2 - published version

Journal ref: Phys. Rev. D 108, 094024 (2023)

Collective modes of a collisional anisotropic quark-gluon plasma

Authors: Ruizhe Zhao, Luhua Qiu, Yun Guo, Michael Strickland

Abstract: In this paper we consider the collective modes of a momentum-space anisotropic quark-gluon plasma taking into account the effect of collisions between the plasma constituents. Our analysis is carried out using a collisional kernel of Bhatnagar-Gross-Krook form and extends prior analyses in the literature by considering all possible angles of propagation of the gluonic modes relative to the momentu… ▽ More In this paper we consider the collective modes of a momentum-space anisotropic quark-gluon plasma taking into account the effect of collisions between the plasma constituents. Our analysis is carried out using a collisional kernel of Bhatnagar-Gross-Krook form and extends prior analyses in the literature by considering all possible angles of propagation of the gluonic modes relative to the momentum-anisotropy axis. We extract both the stable and unstable modes as a function of the collision rate and confirm prior findings that gluonic unstable modes can be eliminated from the spectrum if the collision rate is sufficiently large. In addition, we discuss the conditions necessary for the existence of unstable modes and present evidence that unstable mode growth rates are maximal for modes with momentum along the anisotropy direction. Finally, we demonstrate that when there is a finite collisional rate, gluonic unstable modes are absent from the spectrum at both small and large momentum anisotropy. These results pave the way for understanding the impact of collisions on a variety of non-equilibrium quark-gluon plasma observables. △ Less

Submitted 3 September, 2023; v1 submitted 22 June, 2023; originally announced June 2023.

Comments: 19 pages and 15 figures, minor changes to match the published version

Journal ref: Phys.Rev.D 108 (2023) 3, 034023

Bottomonium suppression at RHIC and LHC in an open quantum system approach

Authors: Michael Strickland, Sabin Thapa

Abstract: We present potential non-relativistic quantum chromodynamics (pNRQCD) predictions for bottomonium suppression in sqrt(sNN) = 200 GeV, 2.76 TeV, and 5.02 TeV heavy-ion collisions using an open quantum systems (OQS) description of the reduced heavy-quark anti-quark density matrix. Compared to prior OQS+pNRQCD studies we include the rapidity dependence of bottomonium production and evolution, allowin… ▽ More We present potential non-relativistic quantum chromodynamics (pNRQCD) predictions for bottomonium suppression in sqrt(sNN) = 200 GeV, 2.76 TeV, and 5.02 TeV heavy-ion collisions using an open quantum systems (OQS) description of the reduced heavy-quark anti-quark density matrix. Compared to prior OQS+pNRQCD studies we include the rapidity dependence of bottomonium production and evolution, allowing for a fully 3-dimensional description of bottomonium trajectories in the quark-gluon plasma. The underlying formalism used to compute the ground and excited state survival probabilities is based on a Lindblad equation that is accurate to next-to-leading order (NLO) in the binding energy over temperature. For the background evolution, we make use of a 3+1D viscous hydrodynamics code which reproduces soft hadron observables at all three collision energies. We find good agreement between NLO OQS+pNRQCD predictions and data taken at LHC energies, however, at RHIC energies, there is tension with recent bottomonium suppression measurements by the STAR collaboration. △ Less

Submitted 28 May, 2023; originally announced May 2023.

Comments: 9 pages, 13 figures

Journal ref: Phys. Rev. D 108, 014031 (2023)

Hot QCD White Paper

Authors: M. Arslandok, S. A. Bass, A. A. Baty, I. Bautista, C. Beattie, F. Becattini, R. Bellwied, Y. Berdnikov, A. Berdnikov, J. Bielcik, J. T. Blair, F. Bock, B. Boimska, H. Bossi, H. Caines, Y. Chen, Y. -T. Chien, M. Chiu, M. E. Connors, M. Csanád, C. L. da Silva, A. P. Dash, G. David, K. Dehmelt, V. Dexheimer , et al. (149 additional authors not shown)

Abstract: Hot QCD physics studies the nuclear strong force under extreme temperature and densities. Experimentally these conditions are achieved via high-energy collisions of heavy ions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). In the past decade, a unique and substantial suite of data was collected at RHIC and the LHC, probing hydrodynamics at the nucleon scale, the… ▽ More Hot QCD physics studies the nuclear strong force under extreme temperature and densities. Experimentally these conditions are achieved via high-energy collisions of heavy ions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). In the past decade, a unique and substantial suite of data was collected at RHIC and the LHC, probing hydrodynamics at the nucleon scale, the temperature dependence of the transport properties of quark-gluon plasma, the phase diagram of nuclear matter, the interaction of quarks and gluons at different scales and much more. This document, as part of the 2023 nuclear science long range planning process, was written to review the progress in hot QCD since the 2015 Long Range Plan for Nuclear Science, as well as highlight the realization of previous recommendations, and present opportunities for the next decade, building on the accomplishments and investments made in theoretical developments and the construction of new detectors. Furthermore, this document provides additional context to support the recommendations voted on at the Joint Hot and Cold QCD Town Hall Meeting, which are reported in a separate document. △ Less

Submitted 30 March, 2023; originally announced March 2023.

Comments: 190 pages, 69 figures

Theoretical and Experimental Constraints for the Equation of State of Dense and Hot Matter

Authors: Rajesh Kumar, Veronica Dexheimer, Johannes Jahan, Jorge Noronha, Jacquelyn Noronha-Hostler, Claudia Ratti, Nico Yunes, Angel Rodrigo Nava Acuna, Mark Alford, Mahmudul Hasan Anik, Debarati Chatterjee, Katerina Chatziioannou, Hsin-Yu Chen, Alexander Clevinger, Carlos Conde, Nikolas Cruz-Camacho, Travis Dore, Christian Drischler, Hannah Elfner, Reed Essick, David Friedenberg, Suprovo Ghosh, Joaquin Grefa, Roland Haas, Alexander Haber , et al. (35 additional authors not shown)

Abstract: This review aims at providing an extensive discussion of modern constraints relevant for dense and hot strongly interacting matter. It includes theoretical first-principle results from lattice and perturbative QCD, as well as chiral effective field theory results. From the experimental side, it includes heavy-ion collision and low-energy nuclear physics results, as well as observations from neutro… ▽ More This review aims at providing an extensive discussion of modern constraints relevant for dense and hot strongly interacting matter. It includes theoretical first-principle results from lattice and perturbative QCD, as well as chiral effective field theory results. From the experimental side, it includes heavy-ion collision and low-energy nuclear physics results, as well as observations from neutron stars and their mergers. The validity of different constraints, concerning specific conditions and ranges of applicability, is also provided. △ Less

Submitted 12 June, 2024; v1 submitted 29 March, 2023; originally announced March 2023.

Journal ref: Living Reviews in Relativity (2024) 27:3

The Present and Future of QCD

Authors: P. Achenbach, D. Adhikari, A. Afanasev, F. Afzal, C. A. Aidala, A. Al-bataineh, D. K. Almaalol, M. Amaryan, D. Androić, W. R. Armstrong, M. Arratia, J. Arrington, A. Asaturyan, E. C. Aschenauer, H. Atac, H. Avakian, T. Averett, C. Ayerbe Gayoso, X. Bai, K. N. Barish, N. Barnea, G. Basar, M. Battaglieri, A. A. Baty, I. Bautista , et al. (378 additional authors not shown)

Abstract: This White Paper presents the community inputs and scientific conclusions from the Hot and Cold QCD Town Meeting that took place September 23-25, 2022 at MIT, as part of the Nuclear Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of 424 physicists registered for the meeting. The meeting highlighted progress in Quantum Chromodynamics (QCD) nuclear physics since the 2015… ▽ More This White Paper presents the community inputs and scientific conclusions from the Hot and Cold QCD Town Meeting that took place September 23-25, 2022 at MIT, as part of the Nuclear Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of 424 physicists registered for the meeting. The meeting highlighted progress in Quantum Chromodynamics (QCD) nuclear physics since the 2015 LRP (LRP15) and identified key questions and plausible paths to obtaining answers to those questions, defining priorities for our research over the coming decade. In defining the priority of outstanding physics opportunities for the future, both prospects for the short (~ 5 years) and longer term (5-10 years and beyond) are identified together with the facilities, personnel and other resources needed to maximize the discovery potential and maintain United States leadership in QCD physics worldwide. This White Paper is organized as follows: In the Executive Summary, we detail the Recommendations and Initiatives that were presented and discussed at the Town Meeting, and their supporting rationales. Section 2 highlights major progress and accomplishments of the past seven years. It is followed, in Section 3, by an overview of the physics opportunities for the immediate future, and in relation with the next QCD frontier: the EIC. Section 4 provides an overview of the physics motivations and goals associated with the EIC. Section 5 is devoted to the workforce development and support of diversity, equity and inclusion. This is followed by a dedicated section on computing in Section 6. Section 7 describes the national need for nuclear data science and the relevance to QCD research. △ Less

Submitted 4 March, 2023; originally announced March 2023.

Comments: QCD Town Meeting White Paper, as submitted to 2023 NSAC LRP committee on Feb. 28, 2023

Journal ref: Nucl.Phys.A 1047 (2024) 122874

Regeneration of bottomonia in an open quantum systems approach

Authors: Nora Brambilla, Miguel Ángel Escobedo, Ajaharul Islam, Michael Strickland, Anurag Tiwari, Antonio Vairo, Peter Vander Griend

Abstract: We demonstrate the importance of quantum jumps in the nonequilibrium evolution of bottomonium states in the quark-gluon plasma. Based on nonrelativistic effective field theory and the open quantum system framework, we evolve the density matrix of color singlet and octet pairs. We show that quantum regeneration of singlet states from octet configurations is necessary to understand experimental resu… ▽ More We demonstrate the importance of quantum jumps in the nonequilibrium evolution of bottomonium states in the quark-gluon plasma. Based on nonrelativistic effective field theory and the open quantum system framework, we evolve the density matrix of color singlet and octet pairs. We show that quantum regeneration of singlet states from octet configurations is necessary to understand experimental results for the suppression of both bottomonium ground and excited states. The values of the heavy-quarkonium transport coefficients used are consistent with recent lattice QCD determinations. △ Less

Submitted 8 August, 2023; v1 submitted 23 February, 2023; originally announced February 2023.

Comments: 5 pages, 7 figures, 1 page supplement; v2 - minor changes, updated references, published version

Report number: TUM-EFT 178/23; FERMILAB-PUB-23-060-V

Journal ref: Phys. Rev. D 108, L011502 (2023)

Hard jet substructure in a multistage approach

Authors: Y. Tachibana, A. Kumar, A. Majumder, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, K. Kauder, L. Kasper, W. Ke , et al. (34 additional authors not shown)

Abstract: We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the JETSCAPE framework. The details of the multistage model and the various parameter choices are described in [A. Kumar et al., arXiv:2204.01163]. A novel feature of this model is the presence of two stages of jet modification: a high virtuality phase [modeled using the… ▽ More We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the JETSCAPE framework. The details of the multistage model and the various parameter choices are described in [A. Kumar et al., arXiv:2204.01163]. A novel feature of this model is the presence of two stages of jet modification: a high virtuality phase [modeled using the modular all twist transverse-scattering elastic-drag and radiation model (MATTER)], where modified coherence effects diminish medium-induced radiation, and a lower virtuality phase [modeled using the linear Boltzmann transport model (LBT)], where parton splits are fully resolved by the medium as they endure multiple scattering induced energy loss. Energy-loss calculations are carried out on event-by-event viscous fluid dynamic backgrounds constrained by experimental data. The uniform and consistent descriptions of multiple experimental observables demonstrate the essential role of modified coherence effects and the multistage modeling of jet evolution. Using the best choice of parameters from [A. Kumar et al., arXiv:2204.01163], and with no further tuning, we present calculations for the medium modified jet fragmentation function, the groomed jet momentum fraction $z_g$ and angular separation $r_g$ distributions, as well as the nuclear modification factor of groomed jets. These calculations provide accurate descriptions of published data from experiments at the Large Hadron Collider. Furthermore, we provide predictions from the multistage model for future measurements at the BNL Relativistic Heavy Ion Collider. △ Less

Submitted 16 October, 2024; v1 submitted 6 January, 2023; originally announced January 2023.

Comments: 20 pages, 12 figures

Journal ref: Phys. Rev. C 110, 044907 (2024)

Bottomonium suppression in the quark-gluon plasma -- From effective field theories to non-unitary quantum evolution

Authors: Michael Strickland

Abstract: In this proceedings contribution I review recent work which computes the suppression of bottomonium production in heavy-ion collisions using open quantum systems methods applied within the potential non-relativistic quantum chromodynamics (pNRQCD) effective field theory. I discuss how the computation of bottomonium suppression can be reduced to solving a Gorini-Kossakowski-Sudarshan-Lindblad (GKSL… ▽ More In this proceedings contribution I review recent work which computes the suppression of bottomonium production in heavy-ion collisions using open quantum systems methods applied within the potential non-relativistic quantum chromodynamics (pNRQCD) effective field theory. I discuss how the computation of bottomonium suppression can be reduced to solving a Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) quantum master equation for the evolution of the b-bbar reduced density matrix. The open quantum systems approach used allows one to take into account the non-equilibrium dynamics and decoherence of bottomonium in the quark-gluon plasma. Finally, I present comparisons of phenomenological predictions obtained using a recently obtained next-to-leading-order GKSL equation with ALICE, ATLAS, and CMS experimental data for bottomonium suppression and elliptic flow. △ Less

Submitted 3 January, 2023; originally announced January 2023.

Comments: 6 pages, 3 figures; Proceedings contribution to Excited QCD 2022, October 23-29 2022, Sicily, Italy

Comprehensive Study of Multi-scale Jet-medium Interaction

Authors: Y. Tachibana, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, W. Ke, M. Kelsey, M. Kordell II, A. Kumar , et al. (33 additional authors not shown)

Abstract: We explore jet-medium interactions at various scales in high-energy heavy-ion collisions using the JETSCAPE framework. The physics of the multi-stage modeling and the coherence effect at high virtuality is discussed through the results of multiple jet and high-$p_{\mathrm{T}}$ particle observables, compared with experimental data. Furthermore, we investigate the jet-medium interaction involved in… ▽ More We explore jet-medium interactions at various scales in high-energy heavy-ion collisions using the JETSCAPE framework. The physics of the multi-stage modeling and the coherence effect at high virtuality is discussed through the results of multiple jet and high-$p_{\mathrm{T}}$ particle observables, compared with experimental data. Furthermore, we investigate the jet-medium interaction involved in the hadronization process. △ Less

Submitted 23 December, 2022; originally announced December 2022.

Comments: 6 pages, 5 figures, contribution to the Quark Matter 2022 proceedings

Journal ref: Acta Phys. Pol. B Proc. Suppl. 16, 1-A50 (2023)

50 Years of Quantum Chromodynamics

Authors: Franz Gross, Eberhard Klempt, Stanley J. Brodsky, Andrzej J. Buras, Volker D. Burkert, Gudrun Heinrich, Karl Jakobs, Curtis A. Meyer, Kostas Orginos, Michael Strickland, Johanna Stachel, Giulia Zanderighi, Nora Brambilla, Peter Braun-Munzinger, Daniel Britzger, Simon Capstick, Tom Cohen, Volker Crede, Martha Constantinou, Christine Davies, Luigi Del Debbio, Achim Denig, Carleton DeTar, Alexandre Deur, Yuri Dokshitzer , et al. (70 additional authors not shown)

Abstract: This paper presents a comprehensive review of both the theory and experimental successes of Quantum Chromodynamics, starting with its emergence as a well defined theory in 1972-73 and following developments and results up to the present day. Topics include a review of the earliest theoretical and experimental foundations; the fundamental constants of QCD; an introductory discussion of lattice QCD,… ▽ More This paper presents a comprehensive review of both the theory and experimental successes of Quantum Chromodynamics, starting with its emergence as a well defined theory in 1972-73 and following developments and results up to the present day. Topics include a review of the earliest theoretical and experimental foundations; the fundamental constants of QCD; an introductory discussion of lattice QCD, the only known method for obtaining exact predictions from QCD; methods for approximating QCD, with special focus on effective field theories; QCD under extreme conditions; measurements and predictions of meson and baryon states; a special discussion of the structure of the nucleon; techniques for study of QCD at high energy, including treatment of jets and showers; measurements at colliders; weak decays and quark mixing; and a section on the future, which discusses new experimental facilities or upgrades currently funded. The paper is intended to provide a broad background for Ph.D. students and postdocs starting their career. Some contributions include personal accounts of how the ideas or experiments were developed. △ Less

Submitted 26 December, 2022; v1 submitted 21 December, 2022; originally announced December 2022.

Comments: Invited volume for the EJPC; 567 pages if text/figures and 4783 references occupying about 160 additional pages. arXiv abstract abridged, for the complete abstract please see the full text

Journal ref: The European Physical Journal C 83 (12), 1125 (2023)

QuantumFDTD -- A computational framework for the relativistic Schrödinger equation

Authors: Rafael L. Delgado, Sebastian Steinbeißer, Michael Strickland, Johannes H. Weber

Abstract: We extend the publicly available quantumfdtd code. It was originally intended for solving the time-independent three-dimensional Schrödinger equation via the finite-difference time-domain (FDTD) method and for extracting the ground, first, and second excited states. We (a) include the case of the relativistic Schrödinger equation and (b) add two optimized FFT-based kinetic energy terms for the non… ▽ More We extend the publicly available quantumfdtd code. It was originally intended for solving the time-independent three-dimensional Schrödinger equation via the finite-difference time-domain (FDTD) method and for extracting the ground, first, and second excited states. We (a) include the case of the relativistic Schrödinger equation and (b) add two optimized FFT-based kinetic energy terms for the non-relativistic case. All the three new kinetic terms are computed using Fast Fourier Transform (FFT). We release the resulting code as version 3 of quantumfdtd. Finally, the code now supports arbitrary external file-based potentials and the option to project out distinct parity eigenstates from the solutions. Our goal is quark models used for phenomenological descriptions of QCD bound states, described by the three-dimensional Schrödinger equation. However, we target any field where solving either the non-relativistic or the relativistic three-dimensional Schrödinger equation is required. △ Less

Submitted 18 November, 2022; originally announced November 2022.

Comments: 7 pages, 2 figures, Contribution to the proceedings of the XVth Quark Confinement and the Hadron Spectrum (CONF15). Aug. 1 - 6, 2022. Stavanger, Norway

Journal ref: EPJ Web Conf. 274 (2022) 04004

Non-equilibrium evolution of quarkonium in medium in the open quantum system approach

Authors: Michael Strickland

Abstract: In this proceedings contribution, I review recent work that aims to provide a more comprehensive and systematic understanding of bottomonium dynamics in the quark-gluon plasma using an open quantum system (OQS) approach that is applied in the framework of the potential non-relativistic QCD (pNRQCD) effective field theory and coupled to realistic hydrodynamical backgrounds that have been tuned to s… ▽ More In this proceedings contribution, I review recent work that aims to provide a more comprehensive and systematic understanding of bottomonium dynamics in the quark-gluon plasma using an open quantum system (OQS) approach that is applied in the framework of the potential non-relativistic QCD (pNRQCD) effective field theory and coupled to realistic hydrodynamical backgrounds that have been tuned to soft hadron observables. I review how the computation of bottomonium suppression can be reduced to solving a Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) equation for the evolution of the b-bbar reduced density matrix, which includes both singlet and octet states plus medium-induced transitions between them at next-to-leading order (NLO) in the binding energy over temperature. Finally, I present comparisons of phenomenological predictions of the NLO OQS+pNRQCD approach and experimental data for bottomonium suppression and elliptic flow in LHC 5.02 TeV Pb-Pb collisions obtained using both smooth and fluctuating hydrodynamic initial conditions. △ Less

Submitted 17 November, 2022; originally announced November 2022.

Comments: 12 pages, 4 figures; Proceedings contribution for the XVth Quark Confinement and the Hadron Spectrum conference, Stavanger, Norway, August 2022. arXiv admin note: text overlap with arXiv:2211.06363

The impact of fluctuating initial conditions on bottomonium suppression in 5.02 TeV heavy-ion collisions

Authors: Huda Alalawi, Jacob Boyd, Chun Shen, Michael Strickland

Abstract: We compute bottomonium suppression and elliptic flow within the pNRQCD effective field theory using an open quantum systems approach. For the hydrodynamical background, we use 2+1D MUSIC second-order viscous hydrodynamics with IP-Glasma initial conditions and evolve bottom/antibottom quantum wave packets in real time in these backgrounds. We find that the impact of fluctuating initial conditions i… ▽ More We compute bottomonium suppression and elliptic flow within the pNRQCD effective field theory using an open quantum systems approach. For the hydrodynamical background, we use 2+1D MUSIC second-order viscous hydrodynamics with IP-Glasma initial conditions and evolve bottom/antibottom quantum wave packets in real time in these backgrounds. We find that the impact of fluctuating initial conditions is small when compared to results obtained using smooth initial conditions. Including the effect of fluctuating initial conditions, we find that the Upsilon(1S) integrated elliptic flow is v_2[1S] = 0.005 +/- 0.002 +/- 0.001, with the first and second variations corresponding to statistical and systematic theoretical uncertainties, respectively. △ Less

Submitted 11 November, 2022; originally announced November 2022.

Comments: 7 pages, 3 figures; 2 page supplement with 3 figures

Journal ref: Phys. Rev. C 107, L031901 (2023)

Long Range Plan: Dense matter theory for heavy-ion collisions and neutron stars

Authors: Alessandro Lovato, Travis Dore, Robert D. Pisarski, Bjoern Schenke, Katerina Chatziioannou, Jocelyn S. Read, Philippe Landry, Pawel Danielewicz, Dean Lee, Scott Pratt, Fabian Rennecke, Hannah Elfner, Veronica Dexheimer, Rajesh Kumar, Michael Strickland, Johannes Jahan, Claudia Ratti, Volodymyr Vovchenko, Mikhail Stephanov, Dekrayat Almaalol, Gordon Baym, Mauricio Hippert, Jacquelyn Noronha-Hostler, Jorge Noronha, Enrico Speranza , et al. (39 additional authors not shown)

Abstract: Since the release of the 2015 Long Range Plan in Nuclear Physics, major events have occurred that reshaped our understanding of quantum chromodynamics (QCD) and nuclear matter at large densities, in and out of equilibrium. The US nuclear community has an opportunity to capitalize on advances in astrophysical observations and nuclear experiments and engage in an interdisciplinary effort in the theo… ▽ More Since the release of the 2015 Long Range Plan in Nuclear Physics, major events have occurred that reshaped our understanding of quantum chromodynamics (QCD) and nuclear matter at large densities, in and out of equilibrium. The US nuclear community has an opportunity to capitalize on advances in astrophysical observations and nuclear experiments and engage in an interdisciplinary effort in the theory of dense baryonic matter that connects low- and high-energy nuclear physics, astrophysics, gravitational waves physics, and data science △ Less

Submitted 7 November, 2022; v1 submitted 3 November, 2022; originally announced November 2022.

Comments: 70 pages, 3 figures, White Paper for the Long Range Plan for Nuclear Science

Report number: LA-UR-22-31648

The effective complex heavy-quark potential in an anisotropic quark-gluon plasma

Authors: Ajaharul Islam, Lihua Dong, Yun Guo, Alexander Rothkopf, Michael Strickland

Abstract: We introduce a method for reducing anisotropic heavy-quark potentials to isotropic potentials by using an effective screening mass that depends on the quantum numbers $l$ and $m$ of a given state. We demonstrate that, using the resulting 1D effective potential model, one can solve a 1D Schrödinger equation and reproduce the full 3D results for the energies and binding energies of low-lying heavy-q… ▽ More We introduce a method for reducing anisotropic heavy-quark potentials to isotropic potentials by using an effective screening mass that depends on the quantum numbers $l$ and $m$ of a given state. We demonstrate that, using the resulting 1D effective potential model, one can solve a 1D Schrödinger equation and reproduce the full 3D results for the energies and binding energies of low-lying heavy-quarkonium bound states to relatively high accuracy. This includes the splitting of different p-wave polarizations. The resulting 1D effective model provides a way to include momentum anisotropy effects in open quantum system simulations of heavy-quarkonium dynamics in the quark-gluon plasma. △ Less

Submitted 21 October, 2022; originally announced October 2022.

Comments: 8 pages, 2 figures, 2 tables. Contribution to the proceedings of the "15th Quark Confinement and the Hadron Spectrum Conference (ConfinementXV)"

Far-from-equilibrium attractors for massive kinetic theory in the relaxation time approximation

Authors: Huda Alalawi, Michael Strickland

Abstract: We investigate whether early and late time attractors for non-conformal kinetic theories exist by computing the time-evolution of a large set of moments of the one-particle distribution function. For this purpose we make use of a previously obtained exact solution of the 0+1D boost-invariant massive Boltzmann equation in relaxation time approximation. We extend prior attractor studies of non-confo… ▽ More We investigate whether early and late time attractors for non-conformal kinetic theories exist by computing the time-evolution of a large set of moments of the one-particle distribution function. For this purpose we make use of a previously obtained exact solution of the 0+1D boost-invariant massive Boltzmann equation in relaxation time approximation. We extend prior attractor studies of non-conformal systems by using a realistic mass- and temperature-dependent relaxation time and explicitly computing the effect of varying both the initial momentum-space anisotropy and initialization time on the time evolution of a large set of integral moments. Our findings are consistent with prior studies, which found that there is an attractor for the scaled longitudinal pressure, but not for the shear and bulk viscous corrections separately. We further present evidence that both late- and early-time attractors exist for all moments of the one-particle distribution function that contain greater than one power of the longitudinal momentum squared. △ Less

Submitted 13 July, 2023; v1 submitted 2 October, 2022; originally announced October 2022.

Comments: 25 pages, 12 figures; v3: fix expression for the non-conformal Navier-Stokes shear-viscous correction; small changes in figures; no changes in the exact solution or conclusions

Journal ref: J. High Energ. Phys. 2022, 143 (2022)

Kaonic Hanbury-Brown-Twiss radii at 200 GeV and 5.02 TeV

Authors: Mubarak Alqahtani, Michael Strickland

Abstract: We use 3+1D quasiparticle anisotropic hydrodynamics (aHydroQP) to make predictions for kaon Hanbury-Brown-Twiss (HBT) radii in 200 GeV and 5.02 TeV heavy-ion collisions. Using previously determined aHydroQP parameters, we compute kaonic HBT radii and their ratios as a function of the mean transverse momentum of the pair $k_T$. We first consider Au-Au collisions at 200 GeV, finding good agreement b… ▽ More We use 3+1D quasiparticle anisotropic hydrodynamics (aHydroQP) to make predictions for kaon Hanbury-Brown-Twiss (HBT) radii in 200 GeV and 5.02 TeV heavy-ion collisions. Using previously determined aHydroQP parameters, we compute kaonic HBT radii and their ratios as a function of the mean transverse momentum of the pair $k_T$. We first consider Au-Au collisions at 200 GeV, finding good agreement between aHydroQP predictions and experimental data up to $k_T \sim 0.8$ GeV. We then present predictions for kaonic HBT radii and their ratios in 5.02 TeV Pb-Pb collisions. Our aHydroQP predictions do not exhibit a clear $k_T$ scaling of the pion and kaon source radii, however, an approximate transverse mass $m_T$ scaling is observed, particularly at 200 GeV. △ Less

Submitted 28 April, 2023; v1 submitted 22 September, 2022; originally announced September 2022.

Comments: 10 pages, 7 figures; v2 - major revision, published version

Bayesian analysis of QGP jet transport using multi-scale modeling applied to inclusive hadron and reconstructed jet data

Authors: R. Ehlers, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, L. Du, T. Dai, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, W. Ke, M. Kelsey, M. Kordell II, A. Kumar, J. Latessa , et al. (33 additional authors not shown)

Abstract: The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response; and Bayesian inference for quantitati… ▽ More The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response; and Bayesian inference for quantitative comparison of model calculations and data. The multi-stage framework incorporates multiple models to cover a broad range in scale of the in-medium parton shower evolution, with dynamical choice of model that depends on the current virtuality or energy of the parton. We will discuss the physics of the multi-stage modeling, and then present a new Bayesian analysis incorporating it. This analysis extends the recently published JETSCAPE determination of the jet transport parameter $\hat{q}$ that was based solely on inclusive hadron suppression data, by incorporating reconstructed jet measurements of quenching. We explore the functional dependence of jet transport coefficients on QGP temperature and jet energy and virtuality, and report the consistency and tensions found for current jet quenching modeling with hadron and reconstructed jet data over a wide range in kinematics and $\sqrt{s_{\text{NN}}}$. This analysis represents the next step in the program of comprehensive analysis of jet quenching phenomenology and its constraint of properties of the QGP. △ Less

Submitted 16 August, 2022; originally announced August 2022.

Comments: 6 pages, 2 figures, contribution to the Quark Matter 2022 proceedings

Multi-scale evolution of charmed particles in a nuclear medium

Authors: JETSCAPE collaboration, W. Fan, G. Vujanovic, S. A. Bass, A. Majumder, A. Angerami, R. Arora, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, K. Kauder, L. Kasper, W. Ke , et al. (35 additional authors not shown)

Abstract: Parton energy-momentum exchange with the quark gluon plasma (QGP) is a multi-scale problem. In this work, we calculate the interaction of charm quarks with the QGP within the higher twist formalism at high virtuality and high energy using the MATTER model, while the low virtuality and high energy portion is treated via a (linearized) Boltzmann Transport (LBT) formalism. Coherence effect that reduc… ▽ More Parton energy-momentum exchange with the quark gluon plasma (QGP) is a multi-scale problem. In this work, we calculate the interaction of charm quarks with the QGP within the higher twist formalism at high virtuality and high energy using the MATTER model, while the low virtuality and high energy portion is treated via a (linearized) Boltzmann Transport (LBT) formalism. Coherence effect that reduces the medium-induced emission rate in the MATTER model is also taken into account. The interplay between these two formalisms is studied in detail and used to produce a good description of the D-meson and charged hadron nuclear modification factor RAA across multiple centralities. All calculations were carried out utilizing the JETSCAPE framework. △ Less

Submitted 13 May, 2023; v1 submitted 1 August, 2022; originally announced August 2022.

Journal ref: 107(5), 2023, 054901

Non-equilibrium attractor in high-temperature QCD plasmas

Authors: Dekrayat Almaalol, Kirill Boguslavski, Aleksi Kurkela, Michael Strickland

Abstract: We establish the existence of a far-from-equilibrium attractor in weakly-coupled gauge theory undergoing 0+1d Bjorken expansion which goes beyond the energy-momentum tensor to the detailed form of the one-particle distribution function. We then demonstrate that the dynamics can be re-scaled at intermediate times and represented by universal exponents. Finally, we assess different procedures for re… ▽ More We establish the existence of a far-from-equilibrium attractor in weakly-coupled gauge theory undergoing 0+1d Bjorken expansion which goes beyond the energy-momentum tensor to the detailed form of the one-particle distribution function. We then demonstrate that the dynamics can be re-scaled at intermediate times and represented by universal exponents. Finally, we assess different procedures for reconstructing the full one-particle distribution function from the energy-momentum tensor along the attractor and discuss implications for the freeze-out procedure used in the phenomenological analysis of ultra-relativistic nuclear collisions △ Less

Submitted 31 July, 2022; originally announced August 2022.

Comments: arXiv admin note: substantial text overlap with arXiv:2004.05195

The complex heavy-quark potential in an anisotropic quark-gluon plasma -- Statics and dynamics

Authors: Lihua Dong, Yun Guo, Ajaharul Islam, Alexander Rothkopf, Michael Strickland

Abstract: We generalize a complex heavy-quark potential model from an isotropic QCD plasma to an anisotropic one by replacing the Debye mass $m_D$ with an anisotropic screening mass depending on the quark pair alignment with respect to the direction of anisotropy. Such an angle-dependent mass is determined by matching the perturbative contributions in the potential model to the exact result obtained in the… ▽ More We generalize a complex heavy-quark potential model from an isotropic QCD plasma to an anisotropic one by replacing the Debye mass $m_D$ with an anisotropic screening mass depending on the quark pair alignment with respect to the direction of anisotropy. Such an angle-dependent mass is determined by matching the perturbative contributions in the potential model to the exact result obtained in the Hard-Thermal-Loop resummed perturbation theory. An advantage of the resulting potential model is that its angular dependence can be effectively described by using a set of angle-averaged screening masses as proposed in our previous work. Consequently, one could solve a one-dimensional Schrödinger equation with a potential model built by changing the anisotropic screening masses into the corresponding angle-averaged ones, and reproduce the full three-dimensional results for the binding energies and decay widths of low-lying quarkonium bound states to very high accuracy. Finally, turning to dynamics, we demonstrate that the one-dimensional effective potential can accurately describe the time evolution of the vacuum overlaps obtained using the full three-dimensional anisotropic potential. This includes the splitting of different p-wave polarizations. △ Less

Submitted 25 September, 2022; v1 submitted 20 May, 2022; originally announced May 2022.

Comments: final version published in JHEP

Journal ref: JHEP 09 (2022) 200

Heavy quarkonium dynamics at next-to-leading order in the binding energy over temperature

Authors: Nora Brambilla, Miguel Ángel Escobedo, Ajaharul Islam, Michael Strickland, Anurag Tiwari, Antonio Vairo, Peter Vander Griend

Abstract: Using the potential non-relativistic quantum chromodynamics (pNRQCD) effective field theory, we derive a Lindblad equation for the evolution of the heavy-quarkonium reduced density matrix that is accurate to next-to-leading order (NLO) in the ratio of the binding energy of the state to the temperature of the medium. The resulting NLO Lindblad equation can be used to more reliably describe heavy-qu… ▽ More Using the potential non-relativistic quantum chromodynamics (pNRQCD) effective field theory, we derive a Lindblad equation for the evolution of the heavy-quarkonium reduced density matrix that is accurate to next-to-leading order (NLO) in the ratio of the binding energy of the state to the temperature of the medium. The resulting NLO Lindblad equation can be used to more reliably describe heavy-quarkonium evolution in the quark-gluon plasma at low temperatures compared to the leading-order truncation. For phenomenological application, we numerically solve the resulting NLO Lindblad equation using the quantum trajectories algorithm. To achieve this, we map the solution of the three-dimensional Lindblad equation to the solution of an ensemble of one-dimensional Schrödinger evolutions with Monte-Carlo sampled quantum jumps. Averaging over the Monte-Carlo sampled quantum jumps, we obtain the solution to the NLO Lindblad equation without truncation in the angular momentum quantum number of the states considered. We also consider the evolution of the system using only the complex effective Hamiltonian without stochastic jumps and find that this provides a reliable approximation for the ground state survival probability at LO and NLO. Finally, we make comparisons with our prior leading-order pNRQCD results and experimental data available from the ATLAS, ALICE, and CMS collaborations. △ Less

Submitted 20 May, 2022; originally announced May 2022.

Comments: 40 pages, 8 figures

Report number: TUM-EFT 169/22

Effective field theory treatment of ${\cal N}=4$ supersymmetric Yang-Mills thermodynamics

Authors: Ubaid Tantary, Jens O. Andersen, Qianqian Du, Michael Strickland

Abstract: At finite temperature the free energy density of ${\cal N}=4$ supersymmetric Yang-Mills can be calculated using resummed perturbation theory through the order $λ^{5/2}$. Effective field theory methods provide a useful alternative approach to streamline these calculations. In this proceedings contribution, I review recent work with my collaborators where we used effective field theory methods to ca… ▽ More At finite temperature the free energy density of ${\cal N}=4$ supersymmetric Yang-Mills can be calculated using resummed perturbation theory through the order $λ^{5/2}$. Effective field theory methods provide a useful alternative approach to streamline these calculations. In this proceedings contribution, I review recent work with my collaborators where we used effective field theory methods to calculate the free energy density of ${\cal N}=4$ supersymmetric Yang-Mills in four spacetime dimensions through second order in the 't Hooft coupling $λ$. At this order the contributions to the free energy density come from the hard scale $T$ and the soft scale $\sqrtλT$. The contribution from the scale $T$ enters through the coefficients in the effective Lagrangian obtained by dimensional reduction and the effects of the scale $gT$ can be calculated using perturbative methods in the effective theory. △ Less

Submitted 18 May, 2022; originally announced May 2022.

Comments: 4 pages, 3 figures; Contribution to the 2022 QCD session of the 56th Rencontres de Moriond

Inclusive jet and hadron suppression in a multistage approach

Authors: A. Kumar, Y. Tachibana, C. Sirimanna, G. Vujanovic, S. Cao, A. Majumder, Y. Chen, L. Du, R. Ehlers, D. Everett, W. Fan, Y. He, J. Mulligan, C. Park, A. Angerami, R. Arora, S. A. Bass, T. Dai, H. Elfner, R. J. Fries, C. Gale, F. Garza, M. Heffernan, U. Heinz, B. V. Jacak , et al. (35 additional authors not shown)

Abstract: We present a new study of jet interactions in the quark-gluon plasma created in high-energy heavy-ion collisions, using a multistage event generator within the JETSCAPE framework. We focus on medium-induced modifications in the rate of inclusive jets and high transverse momentum (high-$p_{\mathrm{T}}$) hadrons. Scattering-induced jet energy loss is calculated in two stages: A high virtuality stage… ▽ More We present a new study of jet interactions in the quark-gluon plasma created in high-energy heavy-ion collisions, using a multistage event generator within the JETSCAPE framework. We focus on medium-induced modifications in the rate of inclusive jets and high transverse momentum (high-$p_{\mathrm{T}}$) hadrons. Scattering-induced jet energy loss is calculated in two stages: A high virtuality stage based on the MATTER model, in which scattering of highly virtual partons modifies the vacuum radiation pattern, and a second stage at lower jet virtuality based on the LBT model, in which leading partons gain and lose virtuality by scattering and radiation. Coherence effects that reduce the medium-induced emission rate in the MATTER phase are also included. The TRENTo model is used for initial conditions, and the (2+1)dimensional VISHNU model is used for viscous hydrodynamic evolution. Jet interactions with the medium are modeled via 2-to-2 scattering with Debye screened potentials, in which the recoiling partons are tracked, hadronized, and included in the jet clustering. Holes left in the medium are also tracked and subtracted to conserve transverse momentum. Calculations of the nuclear modification factor ($R_{\mathrm{AA}}$) for inclusive jets and high-$p_{\mathrm{T}}$ hadrons are compared to experimental measurements at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). Within this framework, we find that with one extra parameter which codifies the transition between stages of jet modification -- along with the typical parameters such as the coupling in the medium, the start and stop criteria etc. -- we can describe these data at all energies for central and semicentral collisions without a rescaling of the jet transport coefficient $\hat{q}$. △ Less

Submitted 16 April, 2023; v1 submitted 3 April, 2022; originally announced April 2022.

Comments: 34 pages, 23 figures

Journal ref: Phys. Rev. C 107, no.3, 034911 (2023)

Nonextensive hydrodynamics of boost-invariant plasmas

Authors: Mubarak Alqahtani, Nasser Demir, Michael Strickland

Abstract: We use quasiparticle anisotropic hydrodynamics to study the non-conformal and non-extensive dynamics of a system undergoing boost-invariant Bjorken expansion. To introduce nonextensivity, we use an underlying Tsallis distribution with a time-dependent nonextensivity parameter $q$. By taking moments of the quasiparticle Boltzmann equation in the relaxation-time approximation, we obtain dynamical eq… ▽ More We use quasiparticle anisotropic hydrodynamics to study the non-conformal and non-extensive dynamics of a system undergoing boost-invariant Bjorken expansion. To introduce nonextensivity, we use an underlying Tsallis distribution with a time-dependent nonextensivity parameter $q$. By taking moments of the quasiparticle Boltzmann equation in the relaxation-time approximation, we obtain dynamical equations which allow us to determine the time evolution of all microscopic parameters including $q$. We compare numerical solutions for bulk observables obtained using the nonextensive evolution with results obtained using quasiparticle anisotropic hydrodynamics with a Boltzmann distribution function ($q \rightarrow 1$). We show that the evolution of the temperature, pressure ratio, and scaled energy density, are quite insensitive to which distribution function is assumed. However, we find significant differences in the early-time evolution of the bulk pressure which are observed for even small deviations from the Boltzmann distribution function. Finally, we discuss the existence of non-conformal hydrodynamic attractors for the longitudinal and transverse pressures, the bulk and shear viscous corrections, and the nonextensivity parameter $q$. △ Less

Submitted 28 March, 2022; originally announced March 2022.

Comments: 24 pages, 5 multipanel figures

Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions

Authors: D. Everett, D. Oliinychenko, M. Luzum, J. -F. Paquet, G. Vujanovic, S. A. Bass, L. Du, C. Gale, M. Heffernan, U. Heinz, L. Kasper, W. Ke, D. Liyanage, A. Majumder, A. Mankolli, C. Shen, D. Soeder, J. Velkovska, A. Angerami, R. Arora, S. Cao, Y. Chen, T. Dai, R. Ehlers, H. Elfner , et al. (31 additional authors not shown)

Abstract: We use a Bayesian-calibrated multistage viscous hydrodynamic model to explore deuteron yield, mean transverse momentum and flow observables in LHC Pb-Pb collisions. We explore theoretical uncertainty in the production of deuterons, including (i) the contribution of thermal deuterons, (ii) models for the subsequent formation of deuterons (hadronic transport vs coalescence) and (iii) the overall sen… ▽ More We use a Bayesian-calibrated multistage viscous hydrodynamic model to explore deuteron yield, mean transverse momentum and flow observables in LHC Pb-Pb collisions. We explore theoretical uncertainty in the production of deuterons, including (i) the contribution of thermal deuterons, (ii) models for the subsequent formation of deuterons (hadronic transport vs coalescence) and (iii) the overall sensitivity of the results to the hydrodynamic model -- in particular to bulk viscosity, which is often neglected in studies of deuteron production. Using physical parameters set by a comparison to only light hadron observables, we find good agreement with measurements of the mean transverse momentum $\langle p_T \rangle$ and elliptic flow $v_2$ of deuterons; however, tension is observed with experimental data for the deuteron multiplicity in central collisions. The results are found to be sensitive to each of the mentioned theoretical uncertainties, with a particular sensitivity to bulk viscosity, indicating that the latter is an important ingredient for an accurate treatment of deuteron production. △ Less

Submitted 15 March, 2022; originally announced March 2022.

Comments: 11 pages, 8 figures

Some recent advances in the understanding of ${\cal N}=4$ supersymmetric Yang-Mills thermodynamics

Authors: Ubaid Tantary, Qianqian Du, Michael Strickland

Abstract: The interest in the thermodynamics of supersymmetric Yang-Mills started after Maldacena proposed the duality between string theory on AdS backgrounds and the large-N limit of SYM theories. One of the motivations to study the thermal properties of ${\cal N}=4$ supersymmetric Yang-Mills in four dimensions (SYM$_{4,4}$) is that at high temperatures, the weak-coupling limit of this theory has many sim… ▽ More The interest in the thermodynamics of supersymmetric Yang-Mills started after Maldacena proposed the duality between string theory on AdS backgrounds and the large-N limit of SYM theories. One of the motivations to study the thermal properties of ${\cal N}=4$ supersymmetric Yang-Mills in four dimensions (SYM$_{4,4}$) is that at high temperatures, the weak-coupling limit of this theory has many similarities with high temperature quantum chromodynamics (QCD). In this proceedings contribution, we review recent calculations of the resummed perturbative free energy of ${\cal N}=4$ supersymmetric Yang-Mills in four spacetime dimensions through second order in the 't Hooft coupling $λ$ at finite temperature and zero chemical potential. We compare our final result with prior results obtained in the weak and strong-coupling limits and construct a generalized Padé approximant that interpolates between the weak-coupling result and the large-$N_c$ strong-coupling result. △ Less

Submitted 4 March, 2022; originally announced March 2022.

Comments: 5 pages, 2 figures; PANIC 2021 proceedings contribution

Long and short distance behavior of the imaginary part of the heavy-quark potential

Authors: Kirill Boguslavski, Babak Kasmaei, Michael Strickland

Abstract: The imaginary part of the effective heavy-quark potential is related to the total in-medium decay width of heavy quark-antiquark bound states. We extract the static limit of this quantity using classical-statistical simulations of real-time Yang-Mills dynamics by measuring the temporal decay of Wilson loops. By performing the simulations on finer and larger lattices, we are able to show that the n… ▽ More The imaginary part of the effective heavy-quark potential is related to the total in-medium decay width of heavy quark-antiquark bound states. We extract the static limit of this quantity using classical-statistical simulations of real-time Yang-Mills dynamics by measuring the temporal decay of Wilson loops. By performing the simulations on finer and larger lattices, we are able to show that the nonperturbative results follow the same form as the perturbative ones. For large quark-antiquark separations, we quantify the magnitude of the non-perturbative long-range corrections to the imaginary part of the heavy-quark potential. We present our results for a wide range of temperatures, lattice spacings, and lattice volumes. We also extract approximations for the short-distance behavior of the classical potential. △ Less

Submitted 23 January, 2022; originally announced January 2022.

Comments: Talk given at the Virtual Tribute to Quark Confinement and the Hadron Spectrum (vConf21), Stavanger, Norway, August 2nd - 6th, 2021

Journal ref: EPJ Web of Conferences 258, 04008 (2022)

Scheme dependence of two-loop HTLpt-resummed $\text{SYM}_{4,4}$ thermodynamics

Authors: Qianqian Du, Ubaid Tantary, Michael Strickland

Abstract: The resummed thermodynamics of ${\cal N}=4$ supersymmetric Yang-Mills theory in four space-time dimensions ($\text{SYM}_{4,4}$) has been calculated previously to two loop order within hard thermal loop perturbation theory (HTLpt) using the canonical dimensional regularization (DRG) scheme. Herein, we revisit this calculation using the regularization by dimensional reduction (RDR) scheme. Since the… ▽ More The resummed thermodynamics of ${\cal N}=4$ supersymmetric Yang-Mills theory in four space-time dimensions ($\text{SYM}_{4,4}$) has been calculated previously to two loop order within hard thermal loop perturbation theory (HTLpt) using the canonical dimensional regularization (DRG) scheme. Herein, we revisit this calculation using the regularization by dimensional reduction (RDR) scheme. Since the RDR scheme manifestly preserves supersymmetry it is the preferred scheme, however, it is important to assess if and by how much the resummed perturbative results depend on the regularization scheme used. Comparing predictions for the scaled entropy obtained using the DRG and RDR schemes we find that for $λ\lesssim 6$ they are numerically very similar. We then compare the results obtained in both schemes with the strict perturbative result, which is accurate up to order $λ^2$, and a generalized Padé approximant constructed from the known large-$N_c$ weak- and strong-coupling expansions. Comparing the strict perturbative expansion of the two-loop HTLpt result with the perturbative expansion to order $λ^2$, we find that both the DRG and RDR HTLpt calculations result in the same scheme-independent predictions for the coefficients at order $λ$, $λ^{3/2}$, and $λ^2 \logλ$, however, at order $λ^2$ there is a residual regularization scheme dependence. △ Less

Submitted 17 April, 2022; v1 submitted 10 January, 2022; originally announced January 2022.

Comments: 16 pages, 3 figures; v2: background on scheme dependence in general QFTs added to introduction, published version

Journal ref: Phys. Rev. D 105, 074004 (2022)

Bottomonium suppression and elliptic flow in heavy-ion collisions

Authors: Michael Strickland

Abstract: In this proceedings contribution I review recent progress concerning the suppression of bottomonium production in the quark-gluon plasma. Making use of open quantum system methods applied to potential non-relativistic quantum chromodynamics one can show that the dynamics of heavy-quarkonium bound states satisfying the scale hierarchy 1/a_0 >> pi T ~ m_D >> E obey a Lindblad equation whose solution… ▽ More In this proceedings contribution I review recent progress concerning the suppression of bottomonium production in the quark-gluon plasma. Making use of open quantum system methods applied to potential non-relativistic quantum chromodynamics one can show that the dynamics of heavy-quarkonium bound states satisfying the scale hierarchy 1/a_0 >> pi T ~ m_D >> E obey a Lindblad equation whose solution provides the quantum evolution of the heavy-quarkonium reduced density matrix. To solve the resulting Lindblad equation we use a quantum trajectories algorithm which allows one to include all possible angular momentum states of the quark-antiquark probe in a scalable manner. We solve the Lindblad equation using a tuned 3+1D dissipative hydrodynamics code for the background temperature evolution. We then consider a large number of Monte-Carlo sampled bottomonium trajectories embedded in this background. This allows us to extract the centrality- and p_T-dependence of the nuclear suppression factor R_AA[Upsilon] and elliptic flow v_2[Upsilon]. We find good agreement between our model predictions and available sqrt(s_NN) = 5.02 TeV Pb-Pb collision experimental data from the ALICE, ATLAS, and CMS collaborations. △ Less

Submitted 29 December, 2021; v1 submitted 21 December, 2021; originally announced December 2021.

Comments: 6 pages, 4 figures; Proceedings contribution for 19th International Conference on Hadron Spectroscopy and Structure, Mexico City, July 26-31, 2021; v2 - update references

${\cal N}=4$ supersymmetric Yang-Mills thermodynamics from effective field theory

Authors: Jens O. Andersen, Qianqian Du, Michael Strickland, Ubaid Tantary

Abstract: The free energy density of ${\cal N}=4$ supersymmetric Yang-Mills theory in four space-time dimensions is derived through second order in the 't Hooft coupling $λ$ at finite temperature using effective-field theory methods. The contributions to the free energy density at this order come from the hard scale $T$ and the soft scale $\sqrtλ T$. The effects of the scale $T$ are encoded in the coefficie… ▽ More The free energy density of ${\cal N}=4$ supersymmetric Yang-Mills theory in four space-time dimensions is derived through second order in the 't Hooft coupling $λ$ at finite temperature using effective-field theory methods. The contributions to the free energy density at this order come from the hard scale $T$ and the soft scale $\sqrtλ T$. The effects of the scale $T$ are encoded in the coefficients of an effective three-dimensional field theory that is obtained by dimensional reduction at finite temperature. The effects of the electric scale $\sqrtλ T$ are taken into account by perturbative calculations in the effective theory. △ Less

Submitted 6 January, 2022; v1 submitted 23 November, 2021; originally announced November 2021.

Comments: 12 pages, 9 figures; v2 - minor typos fixes; published version

Journal ref: Phys. Rev. D 105, 015006 (2022)