Nuclear Theory·nucl-th

Friday·May 19, 2023

11 papers—4 primary·7 cross-listed

01
[Submitted on 18 May 2023]
Thermal photon production in Gubser inviscid relativistic fluid dynamics
Jean-François Paquet🇺🇸
The Gubser solution to inviscid relativistic fluid dynamics is used to examine the role of transverse expansion on the energy spectrum of photons radiated by quark-gluon plasma. Transverse flow is shown to be a modest effect on the energy spectrum of photons as a whole, despite its large effect on rare high-energy photons produced at low temperatures. An exact expression is derived for the volume of the plasma as a function of its temperature. A simple formula is obtained for the energy spectrum of high-energy thermal photons, which is used to relate the inverse slope $T_{eff}$ of the photon spectrum at energy $E$ to the maximum temperature of the plasma $T_{0}$ , finding $T_{eff} \approx T_{0} / (1 + \frac{5}{2} \frac{T _{0}}{E})$ .
Comments:
6 pages, 5 figures; v3: some clarifications in the text and figures; matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
2305.10669 [pdf]
PRC(2023)·14 citations
02
[Submitted on 18 May 2023]
Bottomonium production in pp and heavy-ion collisions
Taesoo Song🇩🇪 · Joerg Aichelin🇫🇷 · Jiaxing Zhao🇫🇷 · Pol Bernard Gossiaux🇫🇷 · Elena Bratkovskaya🇩🇪
We study bottomonium $b b ˉ$ production in pp collisions as well as in heavy-ion collisions, using a quantal density matrix approach. The initial bottom (anti)quarks are provided by the PYTHIA event generator. We solve the Schrödinger equation for the $b b ˉ$ pair, identifying the potential with the free energy, calculated with lattice QCD, to obtain the temperature dependent $b b ˉ$ density matrix as well as the dissociation temperature. The formation of bottomonium is given by projection of the bottomonium density matrix onto the density matrix of the system. With this approach we describe the rapidity and transverse momentum distribution of the $Υ$ (nS) in pp collisions at $s_{NN} =$ 5.02 TeV extending a similar calculation for the charmonium states \cite{Song:2017phm}. We employ the Remler formalism to study the $b b ˉ$ production in heavy ion collisions in which the heavy quarks scatter elastically with partons from the quark gluon plasma (QGP). The elastic scattering of heavy (anti)quark in QGP is realized by the dynamical quasi-particle model (DQPM) and the expanding QGP is modeled by PHSD. We find that a reduction to 10 \% of the scattering cross section for a (anti)bottom quark with a QGP parton reproduces the experimental data. This suggests that due to color neutrality the scattering cross section of the small $b b ˉ$ system with a parton is considerably smaller than twice the bottom-parton scattering cross section.
Comments:
9 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2305.10750 [pdf]
PRC(2023)·29 citations
03
[Submitted on 18 May 2023]
Hyperon global polarization in heavy-ion collisions at NICA energies. Feed-down effects and the role of $Σ^{0}$ hyperons
V. Voronyuk (JINR, Dubna)🇷🇺 · E.E. Kolomeitsev (Matej Bel Univ., Slovakia, JINR, Dubna)🇷🇺 · N.S. Tsegelnik (JINR, Dubna)🇷🇺
Global polarization of hyperons induced by the local vorticity of the medium created in heavy-ion collisions at energies 2.3\,GeV $\leq s_{N N} \leq$ 11.5 GeV is calculated in the parton-hadron-string dynamic (PHSD) model. The separation of spectator nucleons and the fluidization of the generated particle distributions are performed. The polarization of all anti-hyperon species is found significantly larger than that of hyperons. The $Ξ$ hyperons are found to be polarized as strong as $Λ$ s but $Ξ$ hyperons have weaker polarization compared to $Λ$ s. The $Ω$ and $Ω$ polarizations show the strongest dependence on the collision energy. Despite the strong polarization of the produced $Λ$ s and $Λ$ s induced by the vortical flows in the medium, the observed polarization signal is significantly depleted because of the feed down from weak and electromagnetic decays of heavier hyperons. Particularly strong suppression is found to be due to electromagnetic decays of $Σ^{0}$ hyperons, which multiplicities obtained in the transport are poorly constrained both from the microscopic input of the $Σ^{0}$ production reactions and from the experimental data. The final $Λ (Λ)$ polarization signal strongly depends on the $Σ^{0}$ multiplicity generated in the model. With all these effects we can reproduce the measured global $Λ$ polarization in collisions at $s_{N N} = 7.7$ and $11.5$ GeV and the global $Λ$ polarization at 11.5 GeV. For energies $< 3$ GeV, the calculated $Λ$ polarization is smaller than the observed one. The polarization of $Ξ (Ξ)$ hyperons is calculated. The signal of $Ξ (Ξ)$ polarization is argued to be insensitive to feed-down effects and be a more direct probe of the degree of the vorticity in the system.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2305.10792 [pdf]
PRC(2025)·8 citations
04
[Submitted on 18 May 2023]
Direct mapping of tidal deformability to the iso-scalar and iso-vector nuclear matter parameters
Sk Md Adil Imam🇮🇳 · Arunava Mukherjee🇮🇳 · B. K. Agrawal🇮🇳 · Gourab Banerjee🇮🇳
Background: The equations of state (EoSs) which determine the properties of neutron stars (NSs) are often characterized by the iso-scalar and iso-vector nuclear matter parameters (NMPs). Recent attempts to relate the radius and tidal deformability of a NS to the individual NMPs have been inconclusive. These properties display strong correlations with the pressure of NS matter which depends on several NMPs. The knowledge of minimal NMPs that determine the NS properties will be necessary to address any connection between NS properties (e.g., tidal deformability) and that of finite nuclei. Purpose: To identify the important NMPs required to describe the tidal deformability of neutron star for astrophysically relevant range of their gravitational masses (1.2 -- 1.8 M $_{⊙}$ ) as encountered in the binary neutron star merger events. Method: We construct a large set of EoSs using four iso-scalar and five iso-vector NMPs. These EOSs are employed to perform a systematic analysis to isolate the NMPs that predominantly determine the tidal deformability, over a wide range of NS mass. The tidal deformability is then directly mapped to these NMPs. Results: The tidal deformability of the NS with mass 1.2-1.8 M $_{⊙}$ can be determined within 10 $%$ directly in terms of four nuclear matter parameters, namely, the incompressibility $K_{0}$ and skewness $Q_{0}$ of symmetric nuclear matter, and the slope $L_{0}$ and curvature parameter $K_{sym, 0}$ of symmetry energy. Conclusion: A function that quickly estimates the value of tidal deformability in terms of minimal nuclear matter parameters is developed. Our method can also be extended to other NS observables.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
2305.11007 [pdf]
PRC(2024)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE

Thermal photon production in Gubser inviscid relativistic fluid dynamics

Bottomonium production in pp and heavy-ion collisions

Hyperon global polarization in heavy-ion collisions at NICA energies. Feed-down effects and the role of Σ0 hyperons

Direct mapping of tidal deformability to the iso-scalar and iso-vector nuclear matter parameters

Affiliations

Hyperon global polarization in heavy-ion collisions at NICA energies. Feed-down effects and the role of $Σ^{0}$ hyperons