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
08
Constraining nucleon effective masses with flow and stopping observables from the S $π$ RIT experiment
C.Y. Tsang · M. Kurata-Nishimura · M.B. Tsang · W.G. Lynch · Y.X. Zhang · J. Barney · J. Estee · G. Jhang · R. Wang · M. Kaneko · J.W. Lee · T. Isobe and 43 other authors
Properties of the nuclear equation of state (EoS) can be probed by measuring the dynamical properties of nucleus-nucleus collisions. In this study, we present the directed flow ( $v_{1}$ ), elliptic flow ( $v_{2}$ ) and stopping (VarXZ) measured in fixed target Sn + Sn collisions at 270 AMeV with the S $π$ RIT Time Projection Chamber. We perform Bayesian analyses in which EoS parameters are varied simultaneously within the Improved Quantum Molecular Dynamics-Skyrme (ImQMD-Sky) transport code to obtain a multivariate correlated constraint. The varied parameters include symmetry energy, $S_{0}$ , and slope of the symmetry energy, $L$ , at saturation density, isoscalar effective mass, $m_{s}^{*} / m_{N}$ , isovector effective mass, $m_{v}^{*} / m_{N}$ and the in-medium cross-section enhancement factor $η$ . We find that the flow and VarXZ observables are sensitive to the splitting of proton and neutron effective masses and the in-medium cross-section. Comparisons of ImQMD-Sky predictions to the S $π$ RIT data suggest a narrow range of preferred values for $m_{s}^{*} / m_{N}$ , $m_{v}^{*} / m_{N}$ and $η$ .
↳ nucl-exnucl-thPLB(2024)·17 citations
09
Element abundance patterns in stars indicate fission of nuclei heavier than uranium
Ian U. Roederer · Nicole Vassh · Erika M. Holmbeck · Matthew R. Mumpower · Rebecca Surman · John J. Cowan · Timothy C. Beers · Rana Ezzeddine · Anna Frebel · Terese T. Hansen · Vinicius M. Placco · Charli M. Sakari
The heaviest chemical elements are naturally produced by the rapid neutron-capture process (r-process) during neutron star mergers or supernovae. The r-process production of elements heavier than uranium (transuranic nuclei) is poorly understood and inaccessible to experiments, so must be extrapolated using nucleosynthesis models. We examine element abundances in a sample of stars that are enhanced in r-process elements. The abundances of elements Ru, Rh, Pd, and Ag (atomic numbers Z = 44 to 47, mass numbers A = 99 to 110) correlate with those of heavier elements (63 <= Z <= 78, A > 150). There is no correlation for neighboring elements (34 <= Z <= 42 and 48 <= Z <= 62). We interpret this as evidence that fission fragments of transuranic nuclei contribute to the abundances. Our results indicate that neutron-rich nuclei with mass numbers >260 are produced in r-process events.
↳ astro-ph.SRastro-ph.GAastro-ph.HEnucl-ex+1Science(2023)·19 citations
10
On the QCD critical point, Lee-Yang edge singularities and Pade resummations
Gokce Basar🇺🇸
We analyze the trajectory of the Lee-Yang edge singularities of the QCD equation of state in the complex baryon chemical potential ( $μ_{B}$ ) plane for different values of the temperature by using the recent lattice results for the Taylor expansion coefficients up to eighth order in $μ_{B}$ and various resummation techniques that blend in Pade expansions and conformal maps. By extrapolating from this information, we estimate for the location of the QCD critical point, $T_{c} \approx 100$ MeV, $μ_{c} \approx 580$ MeV. We also estimate the crossover slope at the critical point to be $α_{1} \approx 9^{\circ}$ and further constrain the non-universal mapping parameters between the three dimensional Ising model and QCD equations of state.
↳ hep-thnucl-thPRC(2024)·86 citations
11
Hybrid stars in light of the HESS J1731-347 remnant and the PREX-II experiment
P. Laskos-Patkos🇬🇷 · P.S. Koliogiannis🇬🇷 · Ch.C. Moustakidis🇬🇷
The recent analysis on the central compact object in the HESS J1731-347 remnant suggests interestingly small values for its mass and radius. Such an observation favors soft nuclear models that may be challenged by the observation of massive compact stars. In contrast, the recent PREX-II experiment, concerning the neutron skin thickness of $^{208}$ Pb, points towards stiff equations of state that favor larger compact star radii. In the present study, we aim to explore the compatibility between stiff hadronic equations of state (favored by PREX-II) and the HESS J1731-347 remnant in the context of hybrid stars. For the construction of hybrid equations of state we use three widely employed Skyrme models combined with the well-known vector MIT bag model. Furthermore we consider two different scenarios concerning the energy density of the bag. In the first case, that of a constant bag parameter, we find that the resulting hybrid equations of state are strongly disfavored by the observation of $\sim 2 M_{⊙}$ pulsars. However, the introduction of a Gaussian density dependence yields results that are compatible with the conservative $2 M_{⊙}$ constraint. The utilization of recent data based on the observation of PSR J0030+0451, PSR J0952-0607 and GW190814 allows for the imposition of additional constraints on the relevant parameters and the stiffness of the two phases. Interestingly, we find that the derived hybrid equations of state do not satisfy the PSR J0030+0451 constraints in $1 σ$ and only marginally agree with the $2 σ$ estimations. In addition, we estimate that the observation of massive pulsars, like PSR J0952-0607, in combination with the existence of HESS J1731-347, may require a strong phase transition below $\sim 1.7 n_{0}$ . Finally, we show that the supermassive compact object involved in GW190814 could potentially be explained as a rapidly rotating hybrid star.
↳ astro-ph.HEgr-qcnucl-thPRD(2024)·39 citations
12
Supramassive dark objects with neutron star origin
M. Vikiaris🇬🇷 · V. Petousis🇨🇿 · M. Veselsky🇨🇿 · Ch.C. Moustakidis🇬🇷
Till today, the nature of Dark Matter (DM) remains elusive despite all our efforts. This missing matter of the universe has not been observed by the already operating DM direct-detection experiments, but we can infer its gravitational effects. Galaxies and clusters of galaxies are most likely to contain DM trapped to their gravitational field. This leads us to the natural assumption that compact objects might contain DM too. Among the compact objects exist in galaxies, neutron stars are considered as natural laboratories, where theories can be tested, and observational data can be received. Thus, many models of DM have proposed it's presence in those stars. In particular, in the present study we focus on two types of dark matter particles, namely fermions and bosons with a mass range of [0.01-1.5] GeV and self-interaction strength in the range [10 $^{- 4}$ -10 $^{- 1}$ ] MeV $^{- 1}$ . By employing the two-fluid model, we discovered a stable area in the M-R diagram of a celestial formation consisting of neutron star matter and DM that is substantial in size. This formation spans hundreds of kilometers in diameter and possesses a mass equivalent to 100 or more times the Solar mass. To elucidate, this entity resembles an enormous celestial body of DM, with a neutron star at its core. This implies that a supramassive stellar compact entity can exist without encountering any issues of stability and without undergoing a collapse into a black hole. In any case, the present theoretical prediction can, if combined with corresponding observations, shed light on the existence of DM and even more on its basic properties.
↳ astro-ph.HEastro-ph.COastro-ph.GAgr-qc+2PRD(2024)·12 citations
13
Influence of baryon number, strangeness, and electric charge fluctuations at the LHC
Christopher Plumberg🇺🇸 · Dekrayat Almaalol🇺🇸 · Travis Dore🇩🇪 · Jordi Salinas San Martin🇺🇸 · Patrick Carzon🇺🇸 · Debora Mroczek🇺🇸 · Nanxi Yao🇺🇸 · Willian M. Serenone🇺🇸 · Lydia Spychalla🇺🇸 · Matthew Sievert🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
At the Large Hadron Collider it is possible to generate BSQ (baryon, strangeness, and electric) charge density fluctuations from gluon splittings into quark/anti-quark pairs, generated within the ICCING model. In this work, we implement BSQ charge dynamics in a fully integrated framework. We propagate these conserved charges within an upgraded version of the v-USPhydro hydrodynamic model, which conserves the BSQ densities exactly. Our hydrodynamic simulation uses the full 4D equation of state ${T, μ_{B}, μ_{S}, μ_{Q}}$ from lattice Quantum Chromodynamics and includes decays from the Particle Data Group 2016+. We study the dynamical trajectories of fluid cells passing through the QCD phase diagram. We discuss future applications for this new framework.
↳ hep-phnucl-exnucl-th5 citations
14
Small-x structure of oxygen and neon isotopes as seen by the Large Hadron Collider
Giuliano Giacalone🇫🇮 · Bjoern Schenke🇩🇪 · Soeren Schlichting🇺🇸 · Pragya Singh🇩🇪
Results on collisions of $^{16}$ O nuclei performed at the Relativistic Heavy Ion Collider (RHIC) have been presented for the first time at Quark Matter 2023 by the STAR collaboration. $^{16}$ O+ $^{16}$ O collisions are also expected to take place in the near future at the Large Hadron Collider (LHC) at much higher beam energies. We explore the potential of beam-energy-dependent studies for this system to probe small- $x$ dynamics and QCD evolution. We perform 3+1D IP-Glasma simulations to predict the rapidity dependence of the initial geometry of light-ion collisions, focusing on $^{16}$ O+ $^{16}$ O and $^{20}$ Ne+ $^{20}$ Ne collisions at $s_{NN} = 70$ GeV and 7 TeV. The choice of $^{20}$ Ne is motivated by its strongly elongated geometry, which may respond differently to the effect of the high-energy evolution compared to the more spherical $^{16}$ O. We find that smearing induced by soft gluon production at high energy causes mild variations in the initial-state eccentricities as a function of the collision energy. These effects could be resolved in future experiments and deserve further investigation.
↳ hep-phnucl-thEPJ Web Conf.(2024)·7 citations

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