Nuclear Theory·nucl-th

Wednesday·December 13, 2023

14 papers—7 primary·7 cross-listed

01
Bayesian model averaging for nuclear symmetry energy from effective proton-neutron chemical potential difference of neutron-rich nuclei
Mengying Qiu · Bao-Jun Cai · Lie-Wen Chen · Cen-Xi Yuan · Zhen Zhang
The data-driven Bayesian model averaging is a rigorous statistical approach to combining multiple models for a unified prediction. Compared with the individual model, it provides more reliable information, especially for problems involving apparent model dependence. In this work, within both the non-relativistic Skyrme energy density functional and the nonlinear relativistic mean field model, the effective proton-neutron chemical potential difference $Δ μ_{pn}^{*}$ of neutron-rich nuclei is found to be strongly sensitive to the symmetry energy $E_{sym} (ρ)$ around $2 ρ_{0} /3$ , with $ρ_{0}$ being the nuclear saturation density. Given discrepancies on the $Δ μ_{pn}^{*}$ - $E_{sym} (2 ρ_{0} /3)$ correlations between the two models, we carry out a Bayesian model averaging analysis based on Gaussian process emulators to extract the symmetry energy around $2 ρ_{0} /3$ from the measured $Δ μ_{pn}^{*}$ of 5 doubly magic nuclei $^{48}$ Ca, $^{68}$ Ni, $^{88}$ Sr, $^{132}$ Sn and $^{208}$ Pb. Specifically, the $E_{sym} (2 ρ_{0} /3)$ is inferred to be $E_{sym} (2 ρ_{0} /3) = 25. 6_{- 1.3}^{+ 1.4} MeV$ at $1 σ$ confidence level. The obtained constraints on the $E_{sym} (ρ)$ around $2 ρ_{0} /3$ agree well with microscopic predictions and results from other isovector indicators.
nucl-thPLB(2024)·19 citations
02
$g_{A}$ -sensitive $β$ spectral shapes in the mass $A = 86 - 99$ region assessed by the nuclear shell model
Marlom Ramalho · Jouni Suhonen
Recent years have witnessed an expanding interest in experimental studies of $β$ electrons (electrons emitted in $β^{-}$ decay transitions) and their energy distributions, the so-called $β$ -electron spectra. These experiments are interested mainly in $β$ transitions with electron spectra sensitive to the effective value of the weak axial coupling $g_{A}$ . In the present paper we make an extensive search for $g_{A}$ sensitive $β$ spectral shapes in the $A = 86 - 99$ region using the nuclear shell model with the well established Hamiltonians $glekpn$ and $jj45pnb$ , designed to render a good description of the spectroscopic properties of nuclei in this mass region. We have found eight $β^{-}$ decay transitions with various degrees of $g_{A}$ sensitivity. Moreover, these transitions are also important in pinning down the value of the so-called small relativistic vector nuclear matrix element, sNME. In addition, some of the corresponding mother nuclei are important contributors to the antineutrino flux from nuclear reactors. All this means that the found $β$ transitions are potentially of great interest for future rare-events experiments.
nucl-thnucl-exPRC(2024)·10 citations
03
Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei: Theoretical and Phenomenological considerations
Wojciech Brylinski🇵🇱 · Marek Gazdzicki🇵🇱 · Francesco Giacosa🇵🇱 · Mark Gorenstein🇺🇦 · Roman Poberezhnyuk🇺🇦 · Subhasis Samanta🇮🇳
Recently, the NA61/SHINE collaboration at the CERN SPS reported evidence of isospin-symmetry violation in high-energy nuclear collisions [Nature Commun. 16, 2849 (2025)]. The effect was observed in the relative yields of charged and neutral kaons and cannot be explained by known sources of isospin symmetry breaking. In this work, we extend the theoretical and phenomenological aspects of that study. We discuss the historical background and introduce the concepts of isospin transformations and symmetry. Importantly, we relate isospin symmetry to the QCD flavor symmetry, and we present both conceptual and analytical proofs demonstrating the equality of the mean multiplicities of charged and neutral kaons for an initial ensemble of colliding systems that is invariant under charge-symmetry transformation.
nucl-thhep-exhep-phnucl-exActa Phys.Polon.B(2026)·17 citations
04
Incoherent processes in dileptons production in proton-nucleus scattering at high energies
Sergei P. Maydanyuk (1 and 2)🇭🇺 · Gyorgy Wolf (1) ((1) Wigner Research Centre for Physics, Budapest, Hungary, (2) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine)🇭🇺
$Purpose$ : Incoherent processes in production of lepton pairs in the scattering of protons off nuclei are investigated. $Methods$ : New quantum mechanical model is constructed which uses generalization of the nuclear model of emission of photons in the proton-nucleus reactions in region from low up to high energies with inclusion of formalism of production of lepton pairs. $Results$ : (1) Model with the coherent matrix elements is tested for the scattering of protons on the Be nuclei at energy of proton beam $E_{p}$ of 2.1 GeV. The calculated cross section of production of lepton pairs is in good agreement with experimental data obtained by DLS Collaboration. (2) We analyzed dilepton production for nuclei-targets $\isotope [9] B e$ , $\isotope [12] C$ , $\isotope [16] O$ , $\isotope [24] M g$ , $\isotope [44] C a$ , $\isotope [197] A u$ at $E_{p} = 2.1$ GeV. Coherent cross sections of dilepton production are monotonously decreased with increasing of nucleus-target mass. (3) Production of lepton pairs is more intensive at larger $E_{p}$ . (4) For $p + \isotope 9 B e$ at $E_{p} = 2.1$ GeV we analyzed role of incoherent processes in production of pairs of leptons. Inclusion of incoherent proton-nucleon processes to the model improves agreement with experimental data a little. (5) Adding of the longitudinal amplitude of virtual photon suppresses the cross section of dilepton production a little. (6) The incoherent contribution has a leading role in dilepton production (ratio between incoherent and coherent contributions is 10-100). Model provides the full spectrum for $p + \isotope [93] N b$ at $E_{p} = 3.5$ GeV in good agreement with experimental data of HADES collaboration, shows large role of incoherent processes. Conclusion: Results above confirms importance of incoherent processes in study of dilepton production in this reaction.
nucl-thhep-phnucl-exUniverse(2026)·2 citations
05
A new approach to stochastic relativistic fluid dynamics from information flow
Nicki Mullins🇺🇸 · Mauricio Hippert🇺🇸 · Lorenzo Gavassino🇺🇸 · Jorge Noronha🇺🇸
We present a new general formalism for introducing thermal fluctuations in relativistic hydrodynamics, which incorporates recent developments on the causality and stability of relativistic hydrodynamic theories. Our approach is based on the information current, which measures the net amount of information carried by perturbations around equilibrium in a relativistic many-body system. The resulting noise correlators are guaranteed to be observer-independent for thermodynamically stable models. We obtain an effective action within our formalism and discuss its properties.
nucl-thhep-phhep-thEPJ Web Conf.(2024)·2 citations
06
Shell-model treatment of the $β$ decay of $^{99}$ Tc
Marlom Ramalho · Jouni Suhonen
In the present paper we treat the second-forbidden non-unique (2nd-nu) ground-state-to-ground-state $β^{-}$ decay $^{99} Tc (9/ 2^{+}) \to^{99} Ru (5/ 2^{+})$ , with a 100 $%$ branching ratio, within the framework of the nuclear shell model (NSM). The energy spectrum of the electrons emitted in this $β$ -decay transition ( $β$ -electron spectrum) is sensitive to the wave functions of the involved initial ( $9/ 2^{+}$ ) and final ( $5/ 2^{+}$ ) nuclear ground states through the many involved nuclear matrix elements (NME). The $β$ -electron spectrum of this transition is potentially indicative of the effective value, $g_{A}^{eff}$ , of the weak axial coupling, $g_{A}$ , of crucial importance for extraction of information on beyond-the-standard-model physics from the results of the present and future rare-events experiments. We describe the $β$ spectral shape of this decay by using a state-of-the-art $β$ -decay formalism and compute the many involved NME using the well established NSM Hamiltonians $j j 45 p nb$ and $g l e k p n$ . We have found a strong dependence of the $β$ spectral shape on the value of $g_{A}$ making it a good candidate for determination of the value of $g_{A}^{eff}$ through comparison with the corresponding experimental $β$ spectral shape. We have also found an interesting dependence of the $β$ spectral shape on the value of the so-called small relativistic vector NME, sNME, used to match the computed half-life with the measured one.
nucl-thnucl-ex2 citations
07
Probing nuclear structure at the Electron-Ion Collider and in ultra-peripheral nuclear collisions
Heikki Mäntysaari🇫🇮 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸
Within the Color Glass Condensate framework, we demonstrate that exclusive vector meson production at high energy is sensitive to the geometric deformation of the target nucleus and subnucleon scale fluctuations. Deformation of the nucleus enhances the incoherent cross section in the small $∣ t ∣$ region. Subnucleon scale fluctuations increase the incoherent cross section in the large $∣ t ∣$ region. In ultra-peripheral collisions (UPCs), larger deformation leads to a wider distribution of the minimal impact parameter $B_{min}$ required to produce a UPC. This, together with larger incoherent cross sections for larger deformation, results in smaller extracted radii. Our results demonstrate great potential for future studies of nuclear structure in UPCs and electron-ion collisions.
nucl-thhep-phnucl-exEPJ Web Conf.(2024)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Bayesian model averaging for nuclear symmetry energy from effective proton-neutron chemical potential difference of neutron-rich nuclei

gA​-sensitive β spectral shapes in the mass A=86−99 region assessed by the nuclear shell model

Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei: Theoretical and Phenomenological considerations

Incoherent processes in dileptons production in proton-nucleus scattering at high energies

A new approach to stochastic relativistic fluid dynamics from information flow

Shell-model treatment of the β decay of 99Tc

Probing nuclear structure at the Electron-Ion Collider and in ultra-peripheral nuclear collisions

Affiliations

$g_{A}$ -sensitive $β$ spectral shapes in the mass $A = 86 - 99$ region assessed by the nuclear shell model

Shell-model treatment of the $β$ decay of $^{99}$ Tc