Nuclear Theory·nucl-th

Monday·August 11, 2025

9 papers—5 primary·4 cross-listed

01
Mean free path of photons in relativistic heavy ion collisions
Jajati K. Nayak · Rupa Chatterjee
Electromagnetic probes, such as photons and dileptons, play a key role in diagnosing the initial temperature of the hot and dense quark-gluon plasma (QGP) matter created in relativistic nuclear collisions at very high energies. This is due to their large mean free path $λ$ , which allows them to escape the medium without significant interactions. Unlike hadronic particles, which experience multiple scatterings and are affected by the evolving medium, electromagnetic probes carry undistorted information from the initial stages of the expanding system. In this work an attempt has been made to revisit the estimation of mean free paths of photons in QGP phase for a temperature range predicted by hydrodynamics for heavy ion collisions at $s_{N N} = 200$ GeV at RHIC and $s_{N N} = 2.76$ TeV at the LHC. The mean free paths have been estimated for a plasma expanding via (1+1)D and (2+1)D hydrodynamical expansions. For the (1+1)D case, photons with low energy ( $E_{γ} < 0.2$ GeV) coming from a high temperature ( $> 250$ MeV) source are found to have shorter mean free path compared to the expansion scale of the system; while the high energy photons have always larger mean free paths. A similar qualitative nature of the mean free path has also been observed for a more realistic (2+1)D hydrodynamic model calculations although the $λ$ values are found to be larger on a quantitative scale compared to the (1+1)D case.
nucl-thhep-exhep-phIJMPE(2025)·11 citations
02
Wigner Phase-Space Densities of Nuclear Clusters and Hypernuclei
Jiaxing Zhao🇩🇪 · Joerg Aichelin🇫🇷 · Elena Bratkovskaya🇩🇪
We solve the Schrödinger equation for few-body systems to obtain the wave function for light nuclear clusters and hypernuclei from d to $_{ΛΛ}^{5} He$ employing realistic nucleon-nucleon and nucleon- $Λ$ potentials. We project the solution to the hyperspherical harmonic basis states to obtain the corresponding density matrices and the Wigner densities. The experimental root mean square (rms) radii and binding energies of the different clusters are well reproduced. The Wigner densities obtained will allow to improve the present coalescence approaches to identify clusters, created in heavy-ion collisions.
nucl-thhep-phPRC(2025)·4 citations
03
Light nuclei elliptic flow at mid-rapidity in $s_{N N} = 3.0 - 3.9$ GeV Au+Au collisions using coalescence model
Y.Xu🇨🇳 · X.H.He🇨🇳 · Y.P.Zhang🇨🇳
Light nuclei collective flow is an important probe for understanding their production mechanisms in heavy-ion collisions. The STAR collaboration has reported that the atomic mass number ( $A$ ) scaling of light nuclei elliptic flow $v_{2}$ is broken at $s_{N N} = 3.0 - 3.9$ GeV. The observations reveals that, while protons maintain negative $v_{2}$ values at mid-rapidity at both 3.0 and 3.2 GeV, light nuclei $v_{2}$ exhibit a sign change from negative at 3.0 GeV to positive at 3.2 GeV. In this study, we investigate $v_{2}$ of protons and deuterons in mid-central Au+Au Collisions at $s_{N N} =$ 3.0, 3.2, 3.5 and 3.9 GeV using the JAM2 microscopic transport model. Deuterons are formed via nucleon coalescence, with the spatial distance $Δ R$ and momentum difference $Δ P$ between constituent protons and neutrons serving as the coalescence criteria. Our calculations successfully reproduce the sign change in deuteron $v_{2}$ at 3.2 GeV. We observe a strong dependence of nucleon coalescence probability on the azimuthal angle relative to the reaction plane. This effect is primarily driven by the transverse momentum dependence of the mean spatial $⟨ Δ R ⟩$ and momentum $⟨ Δ P ⟩$ separations between nucleon pairs, which vary with the nucleon azimuthal angle. Moreover, our analysis demonstrates that the stiffness of the nuclear equation of state plays a crucial role in determining the energy dependence of this sign change in deuteron $v_{2}$ at $s_{N N} = 3.2$ GeV.
nucl-thNucl.Sci.Tech.(2026)·1 citation
04
Examining potential energy surface through Chebyshev shape parametrization
K. Jyothish · M. S. Suryan Sivadas · A. K. Rhine Kumar
The present study introduce a novel approach, the Chebyshev shape parametrization, to describe the geometric configurations of atomic nuclei, with a particular emphasis on fission dynamics. In this framework, the nuclear surface is represented by a profile function expanded in a Chebyshev polynomial series, with deformation parameters derived analytically under volume conservation and centre-of-mass constraints. The proposed parametrization is shown to be universal robust, and we establish transformation equations that connect it to other widely used shape parametrizations. In the macroscopic approach, the potential energy surface (PES) is computed using the Lublin-Strasbourg Drop (LSD) model, incorporating deformation-dependent energy coefficients expressed in terms of Chebyshev parameters. This enables a detailed investigation of the structural evolution and fission pathways of the nucleus Pa-227 across various deformations, depicting the influence of shape parameters on elongation, asymmetry, and neck formation. Complementing this, microscopic analysis is carried out by calculating single-particle energy levels through diagonalization of the Yukawa-folded mean-field Hamiltonian in a deformed harmonic oscillator basis. The nuclear shape parameters are provided by the Chebyshev parametrization, allowing us to examine shell structure effects at specific deformations. Together, these macroscopic and microscopic studies provide comprehensive insight into the nuclear energy landscape and shape evolution during fission.
nucl-thPhys.Scripta(2026)·0 citations
05
Realistic shell model for ordinary muon capture of sd-shell nuclei
S. L. Lyu🇮🇹 · G. De Gregorio🇮🇹 · T. Fukui🇯🇵 · N. Itaco🇮🇹 · L. Coraggio🇮🇹
We report about a study of the ordinary muon capture in nuclei belonging to the sd shell, an electroweak process that occurs with exchange momenta far larger than ordinary beta decays (approximately 100 MeV). Such a characteristic places this transition in an energy range that is consistent with the neutrinoless double-beta decay, and represents an interesting test for nuclear models to support their predictions of the nuclear matrix elements for such an unobserved process. For the first time, the calculations are carried out within the realistic shell model (RSM), namely employing effective shell-model Hamiltonians and decay operators derived from realistic nuclear forces, without resorting to any empirical adjustment of the coupling constants. This is a chapter of a research program that is aimed to assess the realistic shell model in reproducing the observables related to electroweak processes in nuclei, and then to evaluate the reliability of nuclear matrix elements for the neutrinoless double-beta decay that are calculated within this approach. We calculate the partial capture rates for many nuclear systems in the sd-shell region, as well as their spectroscopic properties, and compare the results with the available experimental counterparts. Such a comparison tests the relevance of a microscopic approach to the renormalization of transition operators to reproduce data and provide solid predictions of unknown observables.
nucl-thhep-exhep-phnucl-exPRC(2025)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Mean free path of photons in relativistic heavy ion collisions

Wigner Phase-Space Densities of Nuclear Clusters and Hypernuclei

Light nuclei elliptic flow at mid-rapidity in sNN​​=3.0−3.9 GeV Au+Au collisions using coalescence model

Examining potential energy surface through Chebyshev shape parametrization

Realistic shell model for ordinary muon capture of sd-shell nuclei

Affiliations

Light nuclei elliptic flow at mid-rapidity in $s_{N N} = 3.0 - 3.9$ GeV Au+Au collisions using coalescence model