Nuclear Theory·nucl-th

Thursday·December 2, 2021

12 papers—2 primary·10 cross-listed

03
[Submitted on 30 Nov 2021] (cross-list from hep-ph)
Fermion and gluon spectral functions far from equilibrium
Kirill Boguslavski🇦🇹 · Tuomas Lappi🇫🇮 · Sören Schlichting🇩🇪
Motivated by the quark-gluon plasma, we develop a simulation method to obtain the spectral function of (Wilson) fermions non-perturbatively in a non-Abelian gauge theory with large gluon occupation numbers [arXiv:2106.11319]. We apply our method to a non-Abelian plasma close to its non-thermal fixed point, i.e., in a far-from-equilibrium self-similar regime, and find mostly very good agreement with perturbative hard loop (HTL) calculations. For the first time, we extract the full momentum dependence of the damping rate of fermionic collective excitations and compare our results to recent non-perturbative extractions of gluonic spectral functions in two and three spatial dimensions [arXiv:2101.02715, arXiv:1804.01966].
Comments:
8 pages, 5 figures; Talk given at the Virtual Tribute to Quark Confinement and the Hadron Spectrum (vConf21), Stavanger, Norway, August 2nd - 6th, 2021
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2112.00030 [pdf]
EPJ Web Conf.(2022)·1 citation
04
[Submitted on 30 Nov 2021] (cross-list from hep-th)
Noether's theorems and the energy-momentum tensor in quantum gauge theories
Adam Freese🇺🇸
Noether's first and second theorems both imply conserved currents that can be identified as an energy-momentum tensor (EMT). The first theorem identifies the EMT as the conserved current associated with global spacetime translations, while the second theorem identifies it as a conserved current associated with local spacetime translations. This work obtains an EMT for quantum electrodynamics and quantum chromodynamics through the second theorem, which is automatically symmetric in its indices and invariant under the expected symmetries (e.g., BRST invariance) without the need for introducing an ad hoc improvement procedure.
Comments:
12 pages, 1 figure, amended with erratum
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2112.00047 [pdf]
PRD(2022)·38 citations
05
[Submitted on 30 Nov 2021] (cross-list from nucl-ex)
Physics with CEBAF at 12 GeV and Future Opportunities
J. Arrington🇺🇸 · M. Battaglieri🇺🇸 · A. Boehnlein🇺🇸 · S.A. Bogacz🇺🇸 · W.K. Brooks🇨🇱 · E. Chudakov🇺🇸 · I. Cloet🇺🇸 · R. Ent🇺🇸 · H. Gao🇺🇸 · J. Grames🇺🇸 · L. Harwood🇺🇸 · X.Ji🇺🇸 and 12 other authors
We summarize the ongoing scientific program of the 12 GeV Continuous Electron Beam Accelerator Facility (CEBAF) and give an outlook into future scientific opportunities. The program addresses important topics in nuclear, hadronic, and electroweak physics including nuclear femtography, meson and baryon spectroscopy, quarks and gluons in nuclei, precision tests of the standard model, and dark sector searches. Potential upgrades of CEBAF are considered, such as higher luminosity, polarized and unpolarized positron beams, and doubling the beam energy.
Comments:
To be published by Progress in Particle and Nuclear Physics in 2022
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2112.00060 [pdf]
PPNP(2022)·132 citations
06
[Submitted on 30 Nov 2021] (cross-list from hep-lat)
Equation of state of QCD at finite chemical potential from an alternative expansion scheme
Paolo Parotto🇺🇸 · Szabolcs Borsanyi🇩🇪 · Zoltan Fodor🇩🇪 · Jana N. Guenther🇩🇪 · Ruben Kara🇩🇪 · Sandor D. Katz🇭🇺 · Attila Pasztor🇭🇺 · Claudia Ratti🇺🇸 · Kalman K. Szabo🇩🇪
The equation of state of Quantum Chromodynamics (QCD) at finite density is currently known only in a limited range in the baryon chemical potential $μ_{B}$ . This is due to fundamental shortcomings of traditional methods such as Taylor expansion around $μ_{B} = 0$ . In this contribution, we present an alternative scheme that displays substantially improved convergence over the Taylor expansion method. We calculate the alternative expansion coefficients in the continuum, and show our results for the thermodynamic observables up to $μ_{B} / T \leq 3.5$ .
Comments:
8 pages, presentation at the 38th International Symposium on Lattice Field Theory, 26th-30th July 2021, Massachusetts Institute of Technology, USA
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2112.00083 [pdf]
PoS(2022)·1 citation
07
[Submitted on 1 Dec 2021] (cross-list from hep-ph)
Role of the effective range in the weak-binding relation
Tomona Kinugawa🇯🇵 · Tetsuo Hyodo🇯🇵
We study the range correction in the weak-binding relation, which relates the internal structure of hadrons with the scattering length and the binding energy. Utilizing the effective field theories, we show that the effective range originates from the derivative coupling interaction as well as from the channel coupling to the bare state, and that the different contributions are not distinguishable. By examining the compositeness in the effective field theories, it is demonstrated that the effective range induces the finite range correction for the weak-binding relation in addition to the previously known contributions. We thus propose to include the range correction in the uncertainty terms of the weak-binding relation.
Comments:
7 pages, Proceedings of the EXA 2021 online conference, 13-17 September 2021
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2112.00249 [pdf]
EPJ Web Conf.(2022)·16 citations
08
[Submitted on 1 Dec 2021] (cross-list from hep-ph)
Charmonium Triangular Flow in High Energy Nuclear Collisions
Jiaxing Zhao🇨🇳 · Baoyi Chen🇨🇳 · Pengfei Zhuang🇨🇳
We calculate, for the first time, $J / ψ$ triangular flow in high energy nuclear collisions. The charmonium motion in medium is controlled by a transport equation with loss and gain terms, and the evolution of the hot medium is governed by a single-shot hydrodynamic equation with a triangularly deformed initial condition. In comparison with the elliptic flow $v_{2}$ , the triangular flow $v_{3}$ comes almost completely from the charmonium regeneration in the quark gluon plasma and therefore is more sensitive to the medium properties.
Comments:
7 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2112.00293 [pdf]
PRC(2022)·17 citations
09
[Submitted on 1 Dec 2021] (cross-list from hep-lat)
Correlated Dirac eigenvalues around the transition temperature on $N_{τ} = 8$ lattices
Heng-Tong Ding🇨🇳 · Wei-Ping Huang🇨🇳 · Min Lin🇨🇳 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Yu Zhang🇯🇵
We investigate the criticality of chiral phase transition manifested in the first and second order derivatives of Dirac eigenvalue spectrum with respect to light quark mass in (2+1)-flavor lattice QCD. Simulations are performed at temperatures from about 137 MeV to 176 MeV on $N_{τ} = 8$ lattices using the highly improved staggered quarks and the tree-level improved Symanzik gauge action. The strange quark mass is fixed to its physical value $m_{s}^{phy}$ and the light quark mass is set to $m_{s}^{phy} /40$ which corresponds to a Goldstone pion mass $m_{π} = 110$ MeV. We find that in contrast to the case at $T ≃ 205$ MeV $m_{l}^{- 1} \partial ρ (λ, m_{l}) / \partial m_{l}$ is no longer equal to $\partial^{2} ρ (λ, m_{l}) / \partial m_{l}^{2}$ and $\partial^{2} ρ (λ, m_{l}) / \partial m_{l}^{2}$ even becomes negative at certain low temperatures. This means that as temperature getting closer to $T_{c}$ $ρ (λ, m_{l})$ is no longer proportional to $m_{l}^{2}$ and thus dilute instanton gas approximation is not valid for these temperatures. We demonstrate the temperature dependence can be factored out in $\partial ρ (λ, m_{l}) / \partial m_{l}$ and $\partial^{2} ρ (λ, m_{l}) / \partial m_{l}^{2}$ at $T \in [137, 153]$ MeV, and then we propose a feasible method to estimate the power $c$ given $ρ \propto m_{l}^{c}$ .
Comments:
Talk presented at the 38th International Symposium on Lattice Field Theory - LATTICE2021, 26th-30th, July, 2021, Zoom/Gather@Massachusetts Institute of Technology
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2112.00318 [pdf]
PoS(2022)·6 citations
10
[Submitted on 1 Dec 2021] (cross-list from hep-lat)
Machine learning Hadron Spectral Functions in Lattice QCD
Shi-Yang Chen🇨🇳 · Heng-Tong Ding🇨🇳 · Fei-Yi Liu🇨🇳 · Gabor Papp🇭🇺 · Chun-Bin Yang🇨🇳
Hadron spectral functions carry all the information of hadrons and are encoded in the Euclidean two-point correlation functions. The extraction of hadron spectral functions from the correlator is a typical ill-posed inverse problem and infinite number of solutions to this problem exists. We propose a novel neural network (sVAE) based on the Variation Auto-Encoder (VAE) and Bayesian theorem. Inspired by the maximum entropy method (MEM) we construct the loss function of the neural work such that it includes a Shannon-Jaynes entropy term and a likelihood term. The sVAE is then trained to provide the most probable spectral functions. For the training samples of spectral function we used general spectral functions produced from the Gaussian Mixture Model. After the training is done we performed the mock data tests with input spectral functions consisting 1) only a free continuum, 2) only a resonance peak, 3) a resonance peak plus a free continuum and 4) a NRQCD motivated spectral function. From the mock data test we find that the sVAE in most cases is comparable to the maximum entropy method in the quality of reconstructing spectral functions and even outperforms the MEM in the case where the spectral function has sharp peaks with insufficient number of data points in the correlator. By applying to temporal correlation functions of charmonium in the pseudoscalar channel obtained in the quenched lattice QCD at 0.75 $T_{c}$ on $12 8^{3} \times 96$ lattices and $1.5$ $T_{c}$ on $12 8^{3} \times 48$ lattices, we find that the resonance peak of $η_{c}$ extracted from both the sVAE and MEM has a substantial dependence on the number of points in the temporal direction ( $N_{τ}$ ) adopted in the lattice simulation and $N_{τ}$ larger than 48 is needed to resolve the fate of $η_{c}$ at 1.5 $T_{c}$ .
Comments:
9 pages, 7 figures. Talk presented at the 38th International Symposium on Lattice Field Theory (Lattice 2021), 26-30 July, 2021, Zoom/Gather@Massachusetts Institute of Technology
Subjects:
High Energy Physics — Lattice (hep-lat); Machine Learning (cs.LG); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2112.00460 [pdf]
PoS(2022)·4 citations
11
[Submitted on 1 Dec 2021] (cross-list from hep-lat)
Correlated Dirac Eigenvalues and Axial Anomaly in Chiral Symmetric QCD
Heng-Tong Ding🇨🇳 · Sheng-Tai Li🇨🇳 · Swagato Mukherjee🇨🇳 · Akio Tomiya🇯🇵 · Xiao-Dan Wang🇺🇸 · Yu Zhang🇺🇸
We investigate the Dirac eigenvalue spectrum ( $ρ (λ, m_{l})$ ) to study the microscopic origin of axial anomaly in high temperature phase of QCD. We propose novel relations between the derivatives ( $\partial^{n} ρ (λ, m_{l}) / \partial m_{l}^{n}$ ) of the Dirac eigenvalue spectrum with respect to the quark mass ( $m_{l}$ ) and the $(n + 1)$ -point correlations among the eigenvalues ( $λ$ ) of the massless Dirac operator. Based on these relations, we present lattice QCD results for $\partial^{n} ρ (λ, m_{l}) / \partial m_{l}^{n}$ ( $n = 1, 2, 3$ ) with $m_{l}$ corresponding to pion masses $m_{π} = 160 - 55$ MeV, and at a temperature of about 1.6 times the chiral phase transition temperature. Calculations were carried out using (2+1)-flavors of highly improved staggered quarks and the tree-level Symanzik gauge action with the physical strange quark mass, three lattice spacings $a = 0.12, 0.08, 0.06$ fm, and lattices having aspect ratios $4 - 9$ . We find that $ρ (λ \to 0, m_{l})$ develops a peaked structure. This peaked structure, which arises due to non-Poisson correlations within the infrared part of the Dirac eigenvalue spectrum, becomes sharper as $a \to 0$ , and its amplitude is proportional to $m_{l}^{2}$ . After continuum and chiral extrapolations, we find that the axial anomaly remains manifested in two-point correlation functions of scalar and pseudo-scalar mesons in the chiral limit. We demonstrate that the behavior of $ρ (λ \to 0, m_{l})$ is responsible for it.
Comments:
9 pages, 4 figures, Contribution to the 38th International Symposium on Lattice Field Theory, LATTICE2021 26th-30th July, 2021 Zoom/Gather@Massachusetts Institute of Technology
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2112.00465 [pdf]
PoS(2022)·4 citations
12
[Submitted on 1 Dec 2021] (cross-list from hep-ph)
Classification of quark and gluon jets in hot QCD medium with deep learning
Yi-Lun Du🇳🇴 · Daniel Pablos🇮🇹 · Konrad Tywoniuk🇳🇴
Deep learning techniques have shown the capability to identify the degree of energy loss of high-energy jets traversing hot QCD medium on a jet-by-jet basis. The average amount of quenching of quark and gluon jets in hot QCD medium actually have different characteristics, such as their dependence on the in-medium traversed length and the early-developed jet substructures in the evolution. These observations motivate us to consider these two types of jets separately and classify them from jet images with deep learning techniques. We find that the classification performance gradually decreases with increasing degree of jet modification. In addition, we discuss the predictive power of different jet observables, such as the jet shape, jet fragmentation function, jet substructures as well as their combinations, in order to address the interpretability of the classification task.
Comments:
5 pages, 4 figures, 1 table, 22nd Particles and Nuclei International Conference (PANIC 2021)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2112.00681 [pdf]
PoS(2022)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE