Nuclear Theory·nucl-th

Friday·February 14, 2020

8 papers—5 primary·3 cross-listed

01
[Submitted on 12 Feb 2020]
Early thermalization and shear viscosity to entropy ratio in heavy-ion collisions at energies of BES, FAIR and NICA
E. Zabrodin🇳🇴 · L. Bravina🇳🇴 · M. Teslyk🇳🇴 · O. Vitiuk🇳🇴
Equilibration of highly excited baryon-rich matter is studied within the microscopic model calculations in A+A collisions at energies of BES, FAIR and NICA. It is shown that the system evolution from the very beginning of the collision can be approximated by relativistic hydrodynamics, although the hot and dense nuclear matter is not in local equilibrium yet. During the evolution of the fireball the extracted values of energy density, net baryon and net strangeness densities are used as an input to Statistical Model (SM) in order to calculate temperature $T$ , chemical potentials $μ_{B}$ and $μ_{S}$ , and entropy density $s$ of the system. Also, they are used as an input for the box with periodic boundary conditions to investigate the momentum correlators in the infinite nuclear matter. Shear viscosity $η$ is calculated according to the Green-Kubo formalism. At all energies, shear viscosity to entropy density ratio shows minimum at time corresponding to maximum baryon density. The ratio dependence on $T, μ_{B}, μ_{S}$ is investigated for both in- and out of equilibrium cases.
Comments:
Proceedings of Quark Matter 2019 - the XXVIIIth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2002.05181 [pdf]
NPA(2021)·5 citations
02
[Submitted on 12 Feb 2020]
Importance of non-flow background on the chiral magnetic wave search
Hao-jie Xu · Jie Zhao · Yicheng Feng · Fuqiang Wang
An observable sensitive to the chiral magnetic wave (CMW) is the charge asymmetry dependence of the $π^{-}$ and $π^{+}$ anisotropic flow difference, $Δ v_{n} (A_{ch})$ . We show that, due to non-flow correlations, the flow measurements by the Q-cumulant method using all charged particles as reference introduce a trivial linear term to $Δ v_{n} (A_{ch})$ . The trivial slope contribution to the triangle flow difference $Δ v_{3} (A_{ch})$ can be negative if the non-flow is dominated by back-to-back pairs. This can explain the observed negative $Δ v_{3} (A_{ch})$ slope in the preliminary STAR data. We further find that the non-flow correlations give rise to additional backgrounds to the slope of $Δ v_{2} (A_{ch})$ from the competition among different pion sources and from the larger multiplicity dilution to $π^{+}$ ( $π^{-}$ ) at positive (negative) $A_{ch}$ .
Comments:
4 pages, 2 figures, contribution to the proceedings of the 28th international conference on ultrarelativistic nucleus-nucleus collisions (Quark Matter 2019)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2002.05220 [pdf]
NPA(2021)·9 citations
03
[Submitted on 13 Feb 2020]
Revisiting Bayesian constraints on the transport coefficients of QCD
J.-F. Paquet🇺🇸 · A. Angerami · S. A. Bass · S. Cao · Y. Chen · J. Coleman · L. Cunqueiro · T. Dai · L. Du · R. Ehlers · H. Elfner · D. Everett and 38 other authors
Multistage models based on relativistic viscous hydrodynamics have proven successful in describing hadron measurements from relativistic nuclear collisions. These measurements are sensitive to the shear and the bulk viscosities of QCD and provide a unique opportunity to constrain these transport coefficients. Bayesian analyses can be used to obtain systematic constraints on the viscosities of QCD, through methodical model-to-data comparisons. In this manuscript, we discuss recent developments in Bayesian analyses of heavy ion collision data. We highlight the essential role of closure tests in validating a Bayesian analysis before comparison with measurements. We discuss the role of the emulator that is used as proxy for the multistage theoretical model. We use an ongoing Bayesian analysis of soft hadron measurements by the JETSCAPE Collaboration as context for the discussion.
Comments:
4 pages, 1 figure, contribution to the Quark Matter 2019 proceedings
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2002.05337 [pdf]
NPA(2021)·26 citations
04
[Submitted on 13 Feb 2020]
Rotation Effects on Mesonic Condensations in Isospin Matter
Hui Zhang🇨🇳 · Defu Hou🇨🇳 · Jin-feng Liao🇺🇸
We investigate the rotation effects on the mesonic condensation in isospin matter . Using the two-flavor NJL effective model with a global rotation, we demonstrate two important effects of the rotation on its phase structure: a rotational suppression of the scalar-channel condensates, in particular the pion condensation region; and a rotational enhancement of the rho condensation region with vector-channel condensate. A new phase diagram for isospin matter under rotation is mapped out on the $ω - μ_{I}$ plane where three distinctive phases, corresponding to $σ$ , $π$ , $ρ$ dominated regions respectively, are separated by a second-order line at low isospin chemical potential and a first-order line at high rotation which are further connected at a tri-critical point.
Comments:
4 pages, proceedings for Quark Matter 2019
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2002.05395 [pdf]
NPA(2021)·3 citations
05
[Submitted on 13 Feb 2020]
Coexistence phase of $^{1} S_{0}$ and $^{3} P_{2}$ superfluids in neutron stars
Shigehiro Yasui🇯🇵 · Daisuke Inotani🇯🇵 · Muneto Nitta🇯🇵
In neutron star matter, there exist $^{1} S_{0}$ superfluids in lower density in the crust while $^{3} P_{2}$ superfluids are believed to exist at higher density deep inside the core. In the latter, depending on the temperature and magnetic field, either the uniaxial nematic phase, the D $_{2}$ -biaxial nematic phase, or the D $_{4}$ -biaxial nematic phase appears. In this paper, we discuss a mixture of the $^{1} S_{0}$ and $^{3} P_{2}$ superfluids and find their coexistence. Adopting the loop expansion and the weak-coupling approximation for the interaction between two neutrons, we obtain the Ginzburg-Landau (GL) free energy in which both of the $^{1} S_{0}$ and $^{3} P_{2}$ condensates are taken into account by including the coupling terms between them. We analyze the GL free energy and obtain the phase diagram for the temperature and magnetic field. We find that the $^{1} S_{0}$ superfluid excludes the $^{3} P_{2}$ superfluid completely in the absence of magnetic field, they can coexist for weak magnetic fields, and the $^{1} S_{0}$ superfluid is expelled by the $^{3} P_{2}$ superfluid at strong magnetic fields, thereby proving the robustness of $^{3} P_{2}$ superfluid against the magnetic field. We further show that the D $_{4}$ -BN phase covers the whole region of the $^{3} P_{2}$ superfluidity as a result of the coupling term, in contrast to the case of a pure $^{3} P_{2}$ superfluid studied before in which the D $_{4}$ -BN phase is realized only under strong magnetic fields. Thus, the D $_{4}$ -BN phase is topologically the most interesting phase, e.g., admitting half-quantized non-Abelian vortices relevant not only in magnetars but also in ordinary neutron stars.
Comments:
14 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Superconductivity (cond-mat.supr-con)
arXiv:
2002.05429 [pdf]
PRC(2020)·16 citations
06
[Submitted on 12 Feb 2020] (cross-list from hep-ph)
Precise determination of proton magnetic radius from electron scattering data
J. M. Alarcón🇪🇸 · D. W. Higinbotham🇺🇸 · C. Weiss🇺🇸
We extract the proton magnetic radius from the high-precision electron-proton elastic scattering cross section data. Our theoretical framework combines dispersion analysis and chiral effective field theory and implements the dynamics governing the shape of the low- $Q^{2}$ form factors. It allows us to use data up to $Q^{2} \sim$ 0.5 GeV $^{2}$ for constraining the radii and overcomes the difficulties of empirical fits and $Q^{2} \to 0$ extrapolation. We obtain a magnetic radius $r_{M}^{p}$ = 0.850 $\pm$ 0.001 (fit 68%) $\pm$ 0.010 (theory full range) fm, significantly different from earlier results obtained from the same data, and close to the extracted electric radius $r_{E}^{p}$ = 0.842 $\pm$ 0.002 (fit) $\pm$ 0.010 (theory) fm.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2002.05167 [pdf]
PRC(2020)·42 citations
07
[Submitted on 12 Feb 2020] (cross-list from hep-ph)
Probing Early-Time Dynamics and Quark-Gluon Plasma Transport Properties with Photons and Hadrons
Charles Gale🇨🇦 · Jean-François Paquet🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸
We use a hybrid model which relies on QCD effective kinetic theory -- K\oMP\oST -- to dynamically bridge the gap between IP-Glasma initial states and viscous hydrodynamics, for the theoretical interpretation of heavy-ion collision results. The hydrodynamic phase is then followed by dynamical freeze-out handled by UrQMD. It is observed that the new pre-equilibrium/pre-hydro phase does influence the extraction of transport coefficients. We also show how the early dynamics is reflected in photon observables.
Comments:
4 pages, 2 figures, contribution to the proceedings of XXVIIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2019)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2002.05191 [pdf]
NPA(2021)·32 citations
08
[Submitted on 13 Feb 2020] (cross-list from hep-ph)
A possible shortcut for neutron-antineutron oscillation through mirror world
Zurab Berezhiani🇮🇹
Existing bounds on the neutron-antineutron mass mixing, $ϵ_{n n ˉ} < few \times 1 0^{- 24}$ eV, impose a severe upper limit on $n - n ˉ$ transition probability, $P_{n n ˉ} (t) < (t /0.1 s)^{2} \times 1 0^{- 18}$ or so, where $t$ is the neutron flight time. Here we propose a new mechanism of $n - n ˉ$ transition which is not induced by direct mass mixing $ϵ_{n n ˉ}$ but is mediated instead by the neutron mixings with the hypothetical states of mirror neutron $n^{'}$ and mirror antineutron $n ˉ^{'}$ . The latter can be as large as $ϵ_{n n^{'}}, ϵ_{n n ˉ^{'}} \sim 1 0^{- 15}$ eV or so, without contradicting present experimental limits and nuclear stability bounds. The probabilities of $n - n^{'}$ and $n - n ˉ^{'}$ transitions, $P_{n n^{'}}$ and $P_{n n ˉ^{'}}$ , depend on environmental conditions in mirror sector, and they can be resonantly amplified by applying the magnetic field of the proper value. This opens up a possibility of $n - n ˉ$ transition with the probability $P_{n n ˉ} ≃ P_{n n^{'}} P_{n n ˉ^{'}}$ which can reach the values $\sim 1 0^{- 8}$ or even larger. For finding this effect in real experiments, the magnetic field should not be suppressed but properly varied. These mixings can be induced by new physics at the scale of few TeV which may also originate a new low scale co-baryogenesis mechanism between ordinary and mirror sectors.
Comments:
10 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2002.05609 [pdf]
EPJC(2021)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE