Nuclear Theory·nucl-th

Wednesday·September 30, 2020

14 papers—5 primary·9 cross-listed

06
[Submitted on 28 Sept 2020] (cross-list from hep-ph)
Modified MIT Bag Models -- part II: QCD phase diagram and hot quark stars
Luiz L. Lopes🇧🇷 · Carline Biesdorf🇧🇷 · K. D. Marquez🇧🇷 · Debora P. Menezes🇧🇷
In the present work we use the modified versions of the MIT bag model, on which both a vector field and a self-interacting term are introduced, to obtain hot quark matter and to investigate the QCD phase diagram. We first analyze two-flavored quark matter constrained to both the freeze-out and the liquid-gas phase transition at the hadronic phase. Later, three-flavored quark matter subject to $β$ equilibrium and charge neutrality is used to compute quark star macroscopic properties, which are confronted with recent observational massive and canonical star radius results. Finally, a comparison with QCD phase diagrams obtained from the Nambu-Jona-Lasinio model is performed.
Comments:
13 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2009.13552 [pdf]
Phys.Scripta(2021)·45 citations
07
[Submitted on 28 Sept 2020] (cross-list from hep-ph)
Studying explicit $U (1)_{A}$ symmetry breaking in hot and magnetised two flavour non-local NJL model constrained using lattice results
Mahammad Sabir Ali🇮🇳 · Chowdhury Aminul Islam🇨🇳 · Rishi Sharma🇮🇳
We study the two flavour non-local Nambu\textemdash Jona-Lasinio (NJL) model in the presence of a magnetic field and explore the chiral crossover in presence of a non-local form of the 't Hooft determinant term. Its coupling is governed by a dimensionless parameter $c$ . This term is responsible for the explicit breaking of $U (1)_{A}$ symmetry. We have attempted a systematic analysis of the model parameters by fitting to self-consistent lattice QCD calculations. Three parameters of the model are fixed by $e B = 0$ results from published lattice QCD on the chiral condensate, the pion decay constant ( $F_{π}$ ), and the pion mass ( $m_{π}$ ). The difference of the $u$ and $d$ quark condensates in the presence of a magnetic field ( $e B$ ) is quite sensitive to $c$ and we fix $c$ using published lattice QCD results for this observable. We see no evidence that $c$ depends on $e B$ . The crossover temperature decreases with increasing $e B$ only for condensate values at the lower end of the allowed values (as already seen in~\cite{Pagura:2016pwr}) and $F_{π}$ at the upper end of the allowed values. We further check our model predictions by calculating the topological susceptibility with the fitted $c$ values and comparing it with lattice results. Since the topological susceptibility is related to the extent of the $U (1)_{A}$ symmetry breaking, we find that it is sensitive to the value of $c$ .
Comments:
24 pages, 13 captioned figures, Results substantially improved: now we have a better prediction for the 't Hooft determinant strength
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.13563 [pdf]
PRD(2021)·16 citations
08
[Submitted on 28 Sept 2020] (cross-list from hep-ph)
On gauge invariance of transverse momentum dependent distributions at small-x
Renaud Boussarie🇺🇸 · Yacine Mehtar-Tani🇺🇸
Transverse momentum dependent (TMD) distributions at small x exhibit a rich infinite twist structure that encompasses the leading twist (partonic) distributions as well as the physics of gluon saturation. Progress to further the connection between the standard TMD framework at moderate x and small x has been recently made. In this context, we show that light cone Wilson line operators at small-x can be formulated in terms of transverse gauge links. This new formulation of small x operators allows a direct matching with the standard leading twist gluon TMD distributions and provides an efficient and general prescription for computing TMD distributions at small x beyond leading twist.
Comments:
5 pages, 10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes 2020)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.13594 [pdf]
PoS(2021)·0 citations
09
[Submitted on 28 Sept 2020] (cross-list from hep-ph)
Resolving the Bethe-Salpeter kernel
Si-Xue Qin🇨🇳 · Craig D. Roberts🇨🇳
A novel method for constructing a Bethe-Salpeter kernel for the meson bound-state problem is described. It produces a closed-form kernel that is symmetry-consistent (discrete and continuous) with the gap equation defined by any admissible gluon-quark vertex. Applicable even when the diagrammatic content of that vertex is unknown, the scheme can foster new synergies between continuum and lattice approaches to strong interactions. The framework is illustrated by demonstrating that the presence of a dressed-quark anomalous magnetic moment in the gluon-quark vertex, an emergent feature of strong interactions, can remedy many defects of widely used meson bound-state kernels, including the level ordering of pseudoscalar and vector meson radial excitations.
Comments:
9 pages, 3 figures. Accepted for publication as an "Express Letter" in Chinese Physics Letters
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.13637 [pdf]
Chin.Phys.Lett.(2021)·50 citations
10
[Submitted on 29 Sept 2020] (cross-list from hep-ph)
Magnetic corrections to the boson self-coupling and boson-fermion coupling in the linear sigma model with quarks
Alejandro Ayala🇲🇽 · José Luis Hernández🇲🇽 · L. A. Hernández🇲🇽 · Ricardo L. S. Farias🇧🇷 · R. Zamora🇨🇱
We compute the magnetic field-induced modifications to the boson self-coupling and the boson-fermion coupling, in the static limit, using an effective model of QCD, the linear sigma model with quarks. The former is computed for arbitrary field strengths as well as using the strong field approximation. The latter is obtained in the strong field limit. The arbitrary field result for the boson self-coupling depends on the ultraviolet renormalization scale and this dependence cannot be removed by a simple vacuum subtraction. Using the strong field result as a guide, we find the appropriate choice for this scale and discuss the physical implications. The boson-fermion coupling depends on the Schwinger's phase and we show how this phase can be treated consistently in such a way that the magnetic field induced vertex modification is both gauge invariant and can be written with an explicit factor corresponding to energy-momentum conservation for the external particles. Both couplings show a modest decrease with the field strength.
Comments:
14 pages, 6 figures, expanded discussion, conclusions unchanged, version to appear in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2009.13740 [pdf]
PRD(2020)·26 citations
11
[Submitted on 29 Sept 2020] (cross-list from hep-lat)
Cold Atom Quantum Simulator for String and Hadron Dynamics in Non-Abelian Lattice Gauge Theory
Raka Dasgupta🇮🇳 · Indrakshi Raychowdhury🇺🇸
We propose an analog quantum simulator for simulating real time dynamics of $(1 + 1)$ -d non-Abelian gauge theory well within the existing capacity of ultracold atom experiments. The scheme calls for the realization of a two-state ultracold fermionic system in a 1-dimensional bipartite lattice, and the observation of subsequent tunneling dynamics. Being based on novel loop string hadron formalism of SU(2) lattice gauge theory, this simulation technique is completely SU(2) invariant and simulates accurate dynamics of physical phenomena such as string breaking and/or pair production. The scheme is scalable, and particularly effective in simulating the theory in weak coupling regime, and also bulk limit of the theory in strong coupling regime up to certain approximations. This paper also presents a numerical benchmark comparison of exact spectrum and real time dynamics of lattice gauge theory to that of the atomic Hamiltonian with experimentally realizable range of parameters.
Comments:
21 pages, 6 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
arXiv:
2009.13969 [pdf]
PRA(2022)·56 citations
12
[Submitted on 29 Sept 2020] (cross-list from hep-ph)
Diffractive deeply inelastic scattering in future electron-ion colliders
D. Bendova🇨🇿 · J. Cepila🇨🇿 · J. G. Contreras🇨🇿 · V. P. Goncalves🇧🇷 · M. Matas🇨🇿
The impact of nonlinear effects in the diffractive observables that will be measured in future electron-ion collisions is investigated. We present, for the first time, the predictions for the diffractive structure function and reduced cross sections derived using the solution to the Balitsky--Kovchegov equation with the collinearly-improved kernel and including the impact-parameter dependence. We demonstrate that the contribution of the diffractive events is enhanced in nuclear collisions and that the study of the ratio between the nuclear and proton predictions will be useful to discriminate among different models of the dipole-target scattering amplitude and, consequently, will allow us to constrain the description of QCD dynamics in parton densities.
Comments:
12 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.14002 [pdf]
EPJC(2021)·22 citations
13
[Submitted on 29 Sept 2020] (cross-list from hep-lat)
Deconfinement critical point of lattice QCD with $N_{f} = 2$ Wilson fermions
Francesca Cuteri🇩🇪 · Owe Philipsen🇩🇪 · Alena Schön🇩🇪 · Alessandro Sciarra🇩🇪
The $SU (3)$ pure gauge theory exhibits a first-order thermal deconfinement transition due to spontaneous breaking of its global $Z_{3}$ center symmetry. When heavy dynamical quarks are added, this symmetry is broken explicitly and the transition weakens with decreasing quark mass until it disappears at a critical point. We compute the critical hopping parameter and the associated pion mass for lattice QCD with $N_{f} = 2$ degenerate standard Wilson fermions on $N_{τ} \in {6, 8, 10}$ lattices, corresponding to lattice spacings $a = 0.12 fm$ , $a = 0.09 fm$ , $a = 0.07 fm$ , respectively. Significant cut-off effects are observed, with the first-order region growing as the lattice gets finer. While current lattices are still too coarse for a continuum extrapolation, we estimate $m_{π}^{c} \approx 4 GeV$ with a remaining systematic error of $\sim 20%$ . Our results allow to assess the accuracy of the LO and NLO hopping expanded fermion determinant used in the literature for various purposes. We also provide a detailed investigation of the statistics required for this type of calculation, which is useful for similar investigations of the chiral transition.
Comments:
12 pages, 6 figures, minor changes to match the version published in PRD
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.14033 [pdf]
PRD(2021)·51 citations
14
[Submitted on 29 Sept 2020] (cross-list from hep-ph)
Cone-size dependent jet spectrum in heavy-ion collisions
Yacine Mehtar-Tani🇳🇴 · Daniel Pablos🇺🇸 · Konrad Tywoniuk🇳🇴
Jets in the vacuum correspond to multi-parton configurations that form via a branching process sensitive to the soft and collinear divergences of QCD. In heavy-ion collisions, energy loss processes that are stimulated via interactions with the medium, affect jet observables in a profound way. Jet fragmentation factorizes into a three-stage process, involving vacuum-like emissions above the medium scale, induced emissions enhanced by the medium length and, finally, long-distance vacuum-like fragmentation. This formalism leads to a novel, non-linear resummation of jet energy loss. In this talk we present new results on the combined effects of small- $R$ resummation and energy loss to compute the $R$ -dependent jet spectrum in heavy-ion collisions.
Comments:
submitted to the proceedings of Hard Probes 2020
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.14054 [pdf]
PoS(2021)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE