Nuclear Theory·nucl-th

Tuesday·May 31, 2022

12 papers—6 primary·6 cross-listed

01
[Submitted on 28 May 2022]
Examination of background effects on light-nuclei yield ratio in relativistic heavy-ion collisions
Shanjin Wu🇨🇳 · Koichi Murase🇨🇳 · Shian Tang🇨🇳 · Huichao Song🇨🇳
The light-nuclei yield ratio is one of the candidates to probe the critical fluctuations of hot QCD matter. In this paper, we investigate the \textit{background effects}, namely the non-critical effects coming from the non-trivial thermal background, on the light-nuclei production within the framework of the coalescence model. Specifically, we analyze the impact of the equilibrium phase-space distribution function of nucleons, $f (r, p)$ , on the light-nuclei yield ratio $N_{t} N_{p} / N_{d}^{2}$ , where $N_{t}$ , $N_{p}$ , and $N_{d}$ denote triton, proton, and deuteron yields. By considering the characteristic function of the phase-space distribution, we systematically expand the yield of light nuclei of $A$ -constituent nucleons, $N_{A}$ , in terms of the \textit{phase-space cumulants}, $⟨ r^{n} p^{m} ⟩_{c}$ . We find that the cumulants up to the second-order are canceled out in the generalized ratio $N_{p}^{B - A} N_{B}^{A - 1} / N_{A}^{B - 1}$ . This means that the dominant background effects including the fireball size, the kinetic freeze-out temperature, and the coordinate--momentum correlations caused by the radial expansion play an insignificant role in the yield ratio, which supports the yield ratio as a useful tool for the critical-point search. We also show several examples of background phase-space distributions for the qualitative illustration. The higher-order cumulants, which correspond to the non-Gaussian shape of the phase-space profile, play an important role in the variation of the yield ratio particularly for the smaller fireball sizes. Qualitatively, the spatial structure of the background decreases the yield ratio, and the azimuthal anisotropy $v_{n}$ increases it. The higher order of the azimuthal anisotropy causes a larger effect on the yield ratio. These results call for the comprehensive future studies of the yield ratio using sophisticated dynamical models.
Comments:
v2:title changed, Fig.1 modified, published on PRC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.14302 [pdf]
PRC(2022)·5 citations
02
[Submitted on 28 May 2022]
The effects of the QCD critical point on the spectra and flow coefficients of hadrons
Sushant K. Singh🇮🇳 · Jan-e Alam🇮🇳
The space-time evolution of the hot and dense fireball of quarks and gluons produced in ultra-relativistic heavy-ion collisions at non-zero baryonic chemical potential and temperature has been studied by using relativistic viscous causal hydrodynamics. For this purpose a numerical code has been developed to solve the relativistic viscous causal hydrodynamics in (3+1)-dimensions with the inclusion of QCD critical point (CP) through the equation of state and scaling behaviour of the transport coefficients. We have evaluated the transverse momentum spectra, directed and elliptic flow coefficients of pions and protons to comprehend the effect of CP on these observables by using this code. It is found that the integration over the entire space-time history of the fireball largely obliterates the effects of CP on the spectra and flow coefficients.
Comments:
14 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2205.14469 [pdf]
PRD(2023)·4 citations
03
[Submitted on 29 May 2022]
Correlations among neutron-proton and neutron-deuteron elastic scattering observables
Yu. Volkotrub · R. Skibiński · J. Golak · H. Witała
We employ two models of the nucleon-nucleon force: the OPE-Gaussian as well as the chiral N4LO and N4LO+ interactions with semilocal regularization in momentum space to study correlations among two-nucleon and three-nucleon elastic scattering observables. These models contain a number of free parameters whose values and covariance matrices are evaluated from a fit to the two-nucleon data. Such detailed knowledge of parameters allows us to create, using various sets of statistically generated parameters, numerous versions of these potentials and next apply them to two- and three-nucleon scattering to make predictions of various observables at the reaction energies up to 200 MeV. This permits a systematic analysis of correlations among two-nucleon and three-nucleon observables, basing on a relatively big sample of predictions. We found that most observables in neutron-proton and neutron-deuteron systems are uncorrelated, but there are exceptions revealing strong correlations, which depend on the reaction energy and scattering angle. This information may be useful for precise fixing free parameters of two-nucleon and three-nucleon forces and for understanding dependencies and correlations between potential parameters and observables.
Comments:
20 pages, 8 pdf figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.14588 [pdf]
PRC(2022)·1 citation
04
[Submitted on 30 May 2022]
Systematic study of fusion barrier characteristics within the relativistic mean-field formalism
Shilpa Rana · Mrutunjaya Bhuyan · Raj Kumar
Background: The nuclear interaction potential and hence the fusion barrier formed between the interacting nuclei are the keys to understanding the complex fusion process dynamics. Purpose: This work intends to explore the fusion barrier characteristics of different target-projectile combinations within the relativistic mean-field (RMF) formalism. Methods: The density distributions of interacting nuclei and the microscopic R3Y NN interaction are obtained from relativistic mean-field (RMF) formalism for non-linear NL1, NL3, TM1, and relativistic-Hartree-Bogoliubov (RHB) approach for DDME2 parameter sets. The fusion and/or capture cross-section for the different reaction systems is calculated using the well-known $ℓ$ -summed Wong model. Results: The barrier height and position of 24 heavy-ion reaction systems are obtained for different nuclear density distributions and effective NN interaction potentials. The comparison of fusion and/or capture cross-section obtained from the $ℓ$ -summed Wong model is made with the available experimental data. Conclusions: The phenomenological M3Y NN potential is observed to give higher barrier heights than the relativistic R3Y NN potential for all the reaction systems. The comparison of results obtained from different relativistic parameter sets shows that the densities from NL1 and TM1 parameter sets give the lowest and highest barrier heights for all the systems under study. We observed higher barrier heights and lower cross-sections for DDR3Y NN potential as compared to density-independent R3Y NN potentials obtained for considered non-linear NL1, NL3 and TM1 parameter sets. According to the present analysis, it is concluded that the NL1 and NL3 parameter sets provide comparatively better overlap with the experimental fusion and/or capture cross-section than the TM1 and DDME2 parameter sets.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.15035 [pdf]
PRC(2022)·19 citations
05
[Submitted on 19 May 2022]
An analysis of the spin density matrix of quarkonium in heavy ion collisions
Kayman J. Gonçalves🇧🇷 · Giorgio Torrieri🇧🇷
In this addendum to [1], we apply the techniques developed in that paper to the $J /Ψ$ and $Υ$ spin alignement measurements in [2]. We argue that while the data points to a maximally impure density matrix, consistent with Cooper-Frye/Statistical model freeze-out, a measurement of the dependence of the $ϕ$ -sensitive coefficients on the azimuthal angle with respect to the reaction plane would be the crucial test of this conclusion.
Comments:
Addendum to arXiv:2104.12941 to take into account quarkonium experimental data we have become aware of since writing that paper
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2205.15087 [pdf]
0 citations
06
[Submitted on 30 May 2022]
Neutron star crust properties: comparison between the compressible liquid-drop model and the extended Thomas-Fermi approach
Guilherme Grams🇧🇪 · Jerome Margueron🇫🇷 · Rahul Somasundaram🇫🇷 · Nicolas Chamel🇧🇪 · Stephane Goriely🇧🇪
We present a detailed analysis of three models predicting the properties of non-uniform matter in the crust of neutron stars: the compressible liquid-drop model, the fourth order Extended Thomas Fermi (ETF) method, and ETF plus Strutinsky integral (ETFSI) correction. The former treats the nuclear clusters as uniform hard spheres, the second takes into account the density distribution which can be different for neutrons and protons, and the last one includes the proton shell effects within the Strutinsky approach. The purpose of this work is to understand the importance of the improvements in the nuclear modeling and to analyze the quantities which are the most sensitive to them. We find that thermodynamic quantities such as pressure, energy and chemical potential, as well as the electron fraction, are in very good agreement among the three models. This confirms previous results where we have shown that the improvement in the finite-size description of the nuclear clusters has a small impact on these quantities, since they are mainly constrained by the bulk properties. The refinements in the finite-size modeling are shown to impact mostly the composition of the nuclear clusters ( $Z_{c l}$ , $N_{c l}$ ) in an ordering which ranks according to the leptodermous expansion. This analysis is performed considering both the r-cluster and the e-cluster representations. The proton shell effects are shown to stabilize $Z_{c l}$ , which consequently impacts the neutron number $N_{c l}$ as well.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.15091 [pdf]
J.Phys.Conf.Ser.(2022)·10 citations
07
[Submitted on 28 May 2022] (cross-list from hep-ph)
Thermal and thermoelectric responses of hot QCD medium in time-varying magnetic fields
Gowthama K K🇮🇳 · Manu Kurian🇮🇳 · Vinod Chandra🇮🇳
The thermal response of the hot QCD matter has been studied in the presence of a time-varying magnetic field. The impact of magnetic field, its time dependence, and the collision aspects of the medium on thermal transport have been studied within the relativistic kinetic theory. The decay time of the magnetic field in the medium seems to have a strong dependence on thermal conductivity. The applicability of the Wiedemann-Franz law for the QCD medium has been investigated in the presence of time-varying external electromagnetic fields. The phenomenological significance of thermal transport in heavy-ion collision experiments has also been investigated by relating the thermal conductivity to the elliptic flow through the Knudsen number. The investigations are extended to study the thermoelectric behavior of hot QCD medium and its dependence on the magnetic field. The time dependent magnetic field is observed to significantly influence the thermoelectric behavior of the medium.
Comments:
11 pages, 6 figures, The version accepted in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2205.14427 [pdf]
PRD(2022)·23 citations
08
[Submitted on 28 May 2022] (cross-list from hep-ph)
Comment on "A phenomenological $π^{-} p$ scattering length from pionic hydrogen''
Evangelos Matsinos
This short technical note addresses a number of issues regarding the estimates of the 2004 paper by Ericson, Loiseau, and Wycech for the corrections $δ_{ϵ}$ and $δ_{Γ}$ , which aim at the removal of the effects of electromagnetic origin from the measurements of the strong-interaction shift $ϵ_{1 s}$ and of the total decay width $Γ_{1 s}$ of the ground state in pionic hydrogen.
Comments:
Nine pages. Minor changes to the first version; correction of Ref. [6]
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2205.14441 [pdf]
1 citation
09
[Submitted on 29 May 2022] (cross-list from hep-ph)
Momentum-dependence of $ρ - ω$ mixing in the pion vector form factor and its effect on $(g - 2)_{μ}$
Yun-Hua Chen🇨🇳 · Meng-Ge Qin🇨🇳
The inclusion of the $ρ - ω$ mixing effect is essential for a precise description of the pion electromagnetic form factor in the $e^{+} e^{-} \to π^{+} π^{-}$ process, which quantifies the two-pion contribution to the anomalous magnetic moment of the muon $a_{μ}$ . In this paper, we analyse the momentum dependence of the $ρ - ω$ mixing by considering loop contributions at the next-to-leading order in the $1/ N_{C}$ expansion within the framework of resonance chiral theory. We revisit the work [Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69 (2018) 1], considering the contribution arising from the kaon mass splitting in the kaon loops and the latest experimental data. We perform two kinds of fits (with momentum-independent or momentum-dependent $ρ - ω$ mixing amplitude) to describe the $e^{+} e^{-} \to π^{+} π^{-}$ and $τ \to ν_{τ} 2 π$ data within the energy region of 600 $\sim$ 900 MeV and the decay width of $ω \to π^{+} π^{-}$ , and compare their results. Our findings indicate that both the momentum-independent and momentum-dependent $ρ - ω$ mixing schemes provide appropriate descriptions of the data. However, the momentum-dependent scheme exhibits greater self-consistency, considering the reasonable imaginary part of the mixing matrix element $Π_{ρ ω}$ obtained. Regarding the contribution to the anomalous magnetic moment of the muon, $a_{μ}^{π π} ∣_{[0.6, 0.9] GeV}$ , the results obtained from the fits considering the momentum-dependent $ρ - ω$ mixing amplitude agree well with those obtained without incorporating the momentum dependence of the $ρ - ω$ mixing, within the margin of errors. Furthermore, based on the fitted values of the relevant parameters, we observe that the decay width of $ω \to π^{+} π^{-}$ is predominantly influenced by the $ρ - ω$ mixing effect.
Comments:
24 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2205.14656 [pdf]
CPC(2023)·1 citation
10
[Submitted on 29 May 2022] (cross-list from hep-ph)
Exposing the dead-cone effect of jet quenching in QCD medium
Yun-Fan Liu🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
When an energetic parton traverses the hot QCD medium it may suffer multiple scattering and lose its energy. The medium-induced gluon radiation for a massive quark will be suppressed relative to that of a light quark due to the dead-cone effect. The development of new declustering techniques of jet evolution makes a direct study of the dead-cone effect in the QCD medium possible for the first time. In this work, we compute the emission angle distribution of the charm-quark initiated splittings in $D^{0}$ meson tagged jet and that of the light parton initiated splittings in an inclusive jet in p+p and Pb+Pb at $5.02$ ~TeV by utilizing the declustering techniques of jet evolution. The heavy quark propagation and indued energy loss in the QCD medium are simulated with the SHELL model based on the Langevin equation. By directly comparing the emission angle distributions of charm-quark-initiated splittings with those of light parton-initiated splittings at the same energy intervals of the initial parton, we provide insights into the fundamental splitting structure in A+A collisions, thereby exploring the possible observation of the dead-cone effect in medium-induced radiation. We further investigate the case of the emission angle distributions normalized to the number of splittings and find the dead-cone effect will broaden the emission angle of the splitting and reduce the possibility to occur such splitting, therefore leading the massive parton to lose less energy. We also find the collisional energy loss mechanism has a negligible impact on the medium modification to the emission angle distribution of the charm-quark initiated splittings for $D^{0}$ -meson tagged jets.
Comments:
7 pages, 4 figures, 2 tables, accepted by CPC
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2205.14668 [pdf]
CPC(2025)·11 citations
11
[Submitted on 30 May 2022] (cross-list from hep-ph)
On the definition of electromagnetic local spatial densities for composite spin- $1/2$ systems
J.Yu. Panteleeva🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · U.-G. Meißner🇩🇪
An unambiguous definition of the electromagnetic spatial densities for a spin-1/2 system is proposed and worked out in the zero average momentum frame and in moving frames. The obtained results are compared with the traditional definition of the densities in terms of the three-dimensional Fourier transforms of the electromagnetic form factors in the Breit frame.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2205.15061 [pdf]
PRD(2022)·36 citations
12
[Submitted on 30 May 2022] (cross-list from quant-ph)
Digital quantum simulation of an extended Agassi model: Using machine learning to disentangle its phase-diagram
Álvaro Sáiz🇪🇸 · José-Enrique García-Ramos🇪🇸 · José Miguel Arias🇪🇸 · Lucas Lamata🇪🇸 · Pedro Pérez-Fernández🇪🇸
A digital quantum simulation for the extended Agassi model is proposed using a quantum platform with eight trapped ions. The extended Agassi model is an analytically solvable model including both short range pairing and long range monopole-monopole interactions with applications in nuclear physics and in other many-body systems. In addition, it owns a rich phase diagram with different phases and the corresponding phase transition surfaces. The aim of this work is twofold: on one hand, to propose a quantum simulation of the model at the present limits of the trapped ions facilities and, on the other hand, to show how to use a machine learning algorithm on top of the quantum simulation to accurately determine the phase of the system. Concerning the quantum simulation, this proposal is scalable with polynomial resources to larger Agassi systems. Digital quantum simulations of nuclear physics models assisted by machine learning may enable one to outperform the fastest classical computers in determining fundamental aspects of nuclear matter.
Comments:
15 pages, 11 figures. New title and minor changes. Published in PRC
Subjects:
Quantum Physics (quant-ph); Nuclear Theory (nucl-th)
arXiv:
2205.15122 [pdf]
PRC(2022)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE