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
05
[Submitted on 17 May 2023] (cross-list from hep-ph)
The Photon Content of the Neutron
Keping Xie🇺🇸 · Bei Zhou🇺🇸 · T.J. Hobbs🇺🇸
In this work, we complete our CT18qed study with the neutron's photon parton distribution function (PDF), which is essential for the nucleus scattering phenomenology. Two methods, CT18lux and CT18qed, based on the LUXqed formalism and the DGLAP evolution, respectively, to determine the neutron's photon PDF have been presented. Various low- $Q^{2}$ non-perturbative variations have been carefully examined, which are treated as additional uncertainties on top of those induced by quark and gluon PDFs. The impacts of the momentum sum rule as well as isospin symmetry violation have been explored, and turn out to be negligible. A detailed comparison with other neutron's photon PDF sets has been performed, which shows a great improvement in the precision and a reasonable uncertainty estimation in our results. Finally, two phenomenological implications are demonstrated with photon-initiated processes: neutrino-nucleus $W$ -boson production, which is important for the near-future TeV--PeV neutrino observations, and the axion-like particle production at a high-energy muon beam-dump experiment.
Comments:
38 pages, 22 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2305.10497 [pdf]
JHEP(2024)·32 citations
06
[Submitted on 18 May 2023] (cross-list from hep-ph)
Hadron-hadron potentials coupled to quark degrees of freedom for exotic hadrons
Ibuki Terashima🇯🇵 · Tetsuo Hyodo🇯🇵
We study the properties of the hadron-hadron potentials and quark-antiquark potentials from the viewpoint of the channel coupling. We demonstrate that, for finite quark masses, the coupling to the two-hadron continuum induces the imaginary part of the quark-antiquark potential, in contrast to the string-breaking phenomena in the static limit. It is also shown that the elimination of the different degrees of freedom induces the nonlocality and energy dependence of the effective potentials. For the obtained nonlocal potentials, we apply two methods of the local approximation proposed previously, the formal derivative expansion and the derivative expansion in the HAL QCD method, by carefully examining the energy dependence of the potential. As an application, we construct a coupled-channel model of $c c ˉ$ and $D^{0} D ˉ^{* 0}$ to describe $X (3872)$ , and discuss the property of the effective $D^{0} D ˉ^{* 0}$ potentials. We confirm that the local approximation by the HAL QCD method works better than the formal derivative expansion also for the energy-dependent potential. At the same time, we show that, in the HAL QCD method, the resulting phase shift is sensitive to the choice of the wavefunction to construct the local potential when the system has a shallow bound state such as $X (3872)$ .
Comments:
12 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.10689 [pdf]
PRC(2023)·11 citations
07
[Submitted on 18 May 2023] (cross-list from hep-ph)
Analysis of $Ξ (1620)$ resonance and $K ˉ Λ$ scattering length with chiral unitary approach
Takuma Nishibuchi🇯🇵 · Tetsuo Hyodo🇯🇵
We study the $Ξ (1620)$ resonance near the $K ˉ Λ$ threshold in the light of the recent experimental constraints. The Belle collaboration have found a resonance peak of $Ξ (1620)$ slightly below the $K ˉ^{0} Λ$ threshold in the $π^{+} Ξ^{-}$ invariant mass spectrum, and the ALICE collaboration have determined the $K^{-} Λ$ scattering length from the measurement of the momentum correlation functions in the heavy ion collisions. Using the effective range expansion, we classify the nature of the pole of the near-threshold eigenstate in terms of the scattering length, in the presence of the decay channel. It is shown that the quasibound state below the threshold can be described by only the scattering length, while the description of the resonance above the threshold requires the contribution from the effective range. Based on the chiral unitary approach, we construct a theoretical model which generates the pole of $Ξ (1620)$ below the $K ˉ Λ$ threshold with relatively narrow width, as reported by the Belle collaboration. It is quantitatively demonstrated that the spectrum of the $Ξ (1620)$ quasibound state is distorted by the effect of the nearby $K ˉ Λ$ threshold. We then construct another model which reproduces the $K^{-} Λ$ scattering length by the ALICE collaboration. In this case, the eigenstate pole does not appear in the physically relevant Riemann sheets, and the spectrum shows a cusp structure at the $K ˉ Λ$ threshold. We finally examine the compatibility of the value of the $K ˉ Λ$ scattering length and the subthreshold pole of $Ξ (1620)$ including the experimental uncertainties.
Comments:
12 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.10753 [pdf]
PRC(2024)·21 citations
08
[Submitted on 18 May 2023] (cross-list from hep-lat)
Microscopic Encoding of Macroscopic Universality: Scaling Properties of Dirac Eigenspectra near QCD Chiral Phase Transition
Heng-Tong Ding🇨🇳 · Wei-Ping Huang🇨🇳 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸
Macroscopic properties of the strong interaction near its chiral phase transition exhibit scaling behaviors, which are the same as those observed close to the magnetic transition in a 3-dimensional classical spin system with $O (4)$ symmetry. We show that the universal scaling properties of the chiral phase transition in Quantum Chromodynamics (QCD) at the macroscale are, in fact, encoded within the microscopic energy levels of its fundamental constituents, the quarks. We establish a connection between the cumulants of the chiral order parameter, i.e., the chiral condensate, and the correlations among the energy levels of quarks, i.e., the eigenspectra of the massless QCD Dirac operator. This relation elucidates how the fluctuations of the chiral condensate arise from the correlations within the infrared part of the energy spectra of quarks, and naturally leads to a generalization of the Banks-Casher relation for the cumulants of the chiral condensate. Then, through (2+1)-flavor lattice QCD calculations with varying light quark masses near the QCD chiral transition, we demonstrate that the correlations among the infrared part of the Dirac eigenvalue spectra exhibit same universal scaling behaviors as expected of the cumulants of the chiral condensate. We find that these universal scaling behaviors extend up to the physical values of the up and down quark masses. Our study reveals how the hidden scaling features at the microscale give rise to the macroscopic universal properties of QCD.
Comments:
5 pages main text + 3 pages supplemental material, version to appear in PRL
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2305.10916 [pdf]
PRL(2023)·16 citations
09
[Submitted on 18 May 2023] (cross-list from astro-ph.HE)
Production of $p$ -nuclei from $r$ -process seeds: the $ν r$ -process
Zewei Xiong · Gabriel Martínez-Pinedo · Oliver Just · Andre Sieverding
We present a new nucleosynthesis process that may take place on neutron-rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard $r$ -process, a sequence of neutron-captures and beta-decays, however with charged-current neutrino absorption reactions on nuclei operating much faster than beta-decays. Once neutron capture reactions freeze-out the produced $r$ -process neutron-rich nuclei undergo a fast conversion of neutrons into protons and are pushed even beyond the $β$ -stability line producing the neutron-deficient $p$ -nuclei. This scenario, which we denote as the $ν r$ -process, provides an alternative channel for the production of $p$ -nuclei and the short-lived nucleus $^{92}$ Nb. We discuss the necessary conditions posed on the astrophysical site for the $ν r$ -process to be realized in nature. While these conditions are not fulfilled by current neutrino-hydrodynamic models of $r$ -process sites, future models, including more complex physics and a larger variety of outflow conditions, may achieve the necessary conditions in some regions of the ejecta.
Comments:
5 pages, 4 figures, published in PRL, including the Supplemental Material
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2305.11050 [pdf]
PRL(2024)·14 citations
10
[Submitted on 18 May 2023] (cross-list from hep-ph)
Renormalization of the gluon distribution function in the background field formalism
Tolga Altinoluk🇵🇱 · Guillaume Beuf🇵🇱 · Jamal Jalilian-Marian🇺🇸
We derive the Leading Order DGLAP evolution of gluon distribution function in the target light cone gauge starting from its standard operator definition. The derivation is performed using the background field formalism also employed in the Color Glass Condensate effective theory of small $x$ QCD. We adopt Mandelstam-Leibbrandt prescription to regulate in an unambiguous way the spurious singularity appearing in the light-cone gauge Feynman propagator. UV divergences are regulated via dimensional regularization. The methods introduced in this paper represent the first steps in the construction of a unified framework for QCD evolution, which could address collinear physics as well as small $x$ physics and gluon saturation.
Comments:
Version 2, 39 pages, 3 figures, major revisions compared to version 1
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.11079 [pdf]
PRD(2025)·19 citations
11
[Submitted on 18 May 2023] (cross-list from hep-lat)
Moments of proton GPDs from the OPE of nonlocal quark bilinears up to NNLO
Shohini Bhattacharya🇺🇸 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Xiang Gao🇺🇸 · Andreas Metz🇺🇸 · Joshua Miller🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Fernanda Steffens🇩🇪 · Yong Zhao🇺🇸
For the first time, we present a lattice QCD determination of Mellin moments of unpolarized generalized parton distributions (GPDs) of the proton from an analysis of the quasi-GPD matrix elements within the short-distance factorization framework. We perform our calculation on an $N_{f}$ =2+1+1 twisted mass fermions ensemble with a clover improvement at lattice spacing $a = 0.093$ fm and a pion mass of $m_{π} = 260$ MeV. Focusing on the zero-skewness case, the iso-vector and iso-scalar quasi-GPDs are calculated from the $γ_{0}$ definition, as well as a recently proposed Lorentz-invariant definition. We utilize data on both symmetric and asymmetric kinematic frames, which allows us to obtain the Mellin moments for several values of the momentum transfer, $- t$ , in the range 0.17 to $2.77 GeV^{2}$ . We use the ratio scheme for GPDs, i.e. renormalization group invariant ratios with leading-twist factorization formula and perturbatively calculated matching coefficients up to the next-next-to-leading order (NNLO) to extract Mellin moments of GPDs, which are consistent with renormalization-group improved results. We compare our determination from quasi-GPDs with the results extracted using standard calculations of Mellin moments of local operators, specifically those related to the electromagnetic and gravitational form factors. We estimated the moments of GPDs up to the fifth ones for the first time. By extrapolating the Mellin moments to $- t = 0$ , we obtained the quark charges, momentum fraction, as well as the angular momentum contributions to the proton spin. The impact parameter space interpretation of the GPD moments is discussed, which provides insights into the spatial distribution of unpolarized quarks and their correlations in the transverse plane of an unpolarized or transversely polarized proton.
Comments:
28 pages, 22 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.11117 [pdf]
PRD(2023)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE