Nuclear Theory·nucl-th

Tuesday·January 19, 2021

13 papers—9 primary·4 cross-listed

10
[Submitted on 15 Jan 2021] (cross-list from hep-ph)
Hyper-order baryon number fluctuations at finite temperature and density
Wei-jie Fu🇨🇳 · Xiaofeng Luo🇨🇳 · Jan M. Pawlowski🇩🇪 · Fabian Rennecke🇺🇸 · Rui Wen🇨🇳 · Shi Yin🇨🇳
Fluctuations of conserved charges are sensitive to the QCD phase transition and a possible critical endpoint in the phase diagram at finite density. In this work, we compute the baryon number fluctuations up to tenth order at finite temperature and density. This is done in a QCD-assisted effective theory that accurately captures the quantum- and in-medium effects of QCD at low energies. A direct computation at finite density allows us to assess the applicability of expansions around vanishing density. By using different freeze-out scenarios in heavy-ion collisions, we translate these results into baryon number fluctuations as a function of collision energy. We show that a non-monotonic energy dependence of baryon number fluctuations can arise in the non-critical crossover region of the phase diagram. Our results compare well with recent experimental measurements of the kurtosis and the sixth-order cumulant of the net-proton distribution from the STAR collaboration. They indicate that the experimentally observed non-monotonic energy dependence of fourth-order net-proton fluctuations is highly non-trivial. It could be an experimental signature of an increasingly sharp chiral crossover and may indicate a QCD critical point. The physics implications and necessary upgrades of our analysis are discussed in detail.
Comments:
23 pages, 14 figures, 2 tables, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.06035 [pdf]
PRD(2021)·130 citations
11
[Submitted on 17 Jan 2021] (cross-list from hep-th)
Unruh effect and information entropy approach
M.V. Teslyk🇺🇦 · O.M. Teslyk🇺🇦 · L.V. Zadorozhna🇺🇦 · L. Bravina🇳🇴 · E. Zabrodin🇳🇴
Total entropy generated by the Unruh effect is calculated within the framework of information theory. In contrast to previous studies, here the calculations are done for the finite time of existence of the non-inertial reference frame. In this case only the finite number of particles is produced. Dependence on mass of the emitted particles is taken into account. Analytic expression for the entropy of radiated boson and fermion spectra is derived. We study also its asymptotics corresponding to limiting cases of low and high acceleration. The obtained results can be further generalized to other intrinsic degrees of freedom of the emitted particles, such as spin and electric charge.
Comments:
REVTEX, 8 pages, 5 figures
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2101.06668 [pdf]
Particles(2022)·6 citations
12
[Submitted on 17 Jan 2021] (cross-list from hep-ph)
Journey to the Bound States
Paul Hoyer🇫🇮
Guided by the observed properties of hadrons I formulate a perturbative bound state method for QED and QCD. The expansion starts with valence Fock states ( $e^{+} e^{-}, q q ˉ, q q q, g g$ ) bound by the instantaneous interaction of temporal gauge ( $A^{0} = 0$ ). The method is tested on Positronium atoms at rest and in motion, including hyperfine splitting at $O (α^{4})$ , electromagnetic form factors and deep inelastic scattering. Relativistic binding is studied for QED in $D = 1 + 1$ dimensions, demonstrating the frame independence of the DIS electron distribution and its sea for $x_{bj} \to 0$ . In QCD a homogeneous solution of Gauss' constraint in $D = 3 + 1$ implies $O (α_{s}^{0})$ confining potentials for $q q ˉ, q q ˉ g, q q q$ and $g g$ states, whereas $q q ˉ q q ˉ$ is unconfined. Meson states lie on linear Regge trajectories and have the required frame dependence. A scalar bound state with vanishing four-momentum causes spontaneous chiral symmetry breaking when mixed with the vacuum. These lecture notes assume knowledge of field theory methods, but not of bound states. Brief reviews of existing bound state methods and Dirac electron states are included. Solutions to the exercises are given in the Appendix.
Comments:
105 pages, 22 figures. Expanded version of lectures presented at the University of Pavia in January 2020. v2 added chapter: II. Features of hadrons. Version accepted for publication in SpringerBriefs in Physics
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.06721 [pdf]
SpringerBriefs in Physics (Springer, 2021)·12 citations
13
[Submitted on 18 Jan 2021] (cross-list from hep-ph)
Heavy-hadron molecular spectrum from light-meson exchange saturation
Fang-Zheng Peng🇨🇳 · Mario Sánchez Sánchez🇫🇷 · Mao-Jun Yan🇨🇳 · Manuel Pavon Valderrama🇨🇳
If known, the spectrum of heavy-hadron molecules will be a key tool to disentangle the nature of the exotic states that are being discovered in experiments. Here we argue that the general features of the molecular spectrum can be deduced from the idea that the short-range interaction between the heavy hadrons is effectively described by scalar and vector meson exchange, i.e. the $σ$ , $ω$ and $ρ$ mesons. By means of a contact-range theory where the couplings are saturated by the aforementioned light mesons we are indeed able to postdict the $X (3872)$ (as a $D^{*} D ˉ$ molecule) from the three $P_{c} (4312)$ , $P_{c} (4440)$ and $P_{c} (4457)$ pentaquarks (as $D ˉ Σ_{c}$ and $D ˉ^{*} Σ_{c}$ molecules). We predict a $J^{P C} = 1^{--}$ $D D ˉ_{1}$ molecule at $4240 - 4260 MeV$ which might support the hypothesis that the $Y (4260)$ is at least partly molecular. The extension of these ideas to the light baryons requires minor modifications, after which we recover approximate SU(4)-Wigner symmetry in the two-nucleon system and approximately reproduce the masses of the deuteron and the virtual state.
Comments:
13 pages, 1 table; corresponds to the published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2101.07213 [pdf]
PRD(2022)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hyper-order baryon number fluctuations at finite temperature and density

Unruh effect and information entropy approach

Journey to the Bound States

Heavy-hadron molecular spectrum from light-meson exchange saturation

Affiliations