Nuclear Theory·nucl-th

Monday·June 24, 2024

11 papers—7 primary·4 cross-listed

01
New $^{63}$ Ga(p, $γ$ ) $^{64}$ Ge and $^{64}$ Ge(p, $γ$ ) $^{65}$ As reaction rates corresponding to the temperature regime of thermonuclear X-ray bursts
Ning Lu · Yi Hua Lam · Alexander Heger · Zi Xin Liu · Hidetoshi Yamaguchi
We compute the $^{63}$ Ga(p, $γ$ ) $^{64}$ Ge and $^{64}$ Ge(p, $γ$ ) $^{65}$ As thermonuclear reaction rates using the latest experimental input supplemented with theoretical nuclear spectroscopic information. The experimental input consists of the latest proton thresholds of $^{64}$ Ge and $^{65}$ As, and the nuclear spectroscopic information of $^{65}$ As, whereas the theoretical nuclear spectroscopic information for $^{64}$ Ge and $^{65}$ As are deduced from the full pf-shell space configuration-interaction shell-model calculations with the GXPF1A Hamiltonian. Both thermonuclear reaction rates are determined with known uncertainties at the energies that correspond to the Gamow windows of the temperature regime relevant to Type I X-ray bursts, covering the typical temperature range of the thermonuclear runaway of the GS 1826 $-$ 24 periodic bursts and SAX J1808.4 $-$ 3658 photospheric radius expansion bursts.
nucl-thastro-ph.HEnucl-exPRC(2024)·4 citations
02
Symplectic symmetry approach to clustering in atomic nuclei: The case of $^{24}$ Mg
H. G. Ganev
Symplectic symmetry approach to clustering (SSAC) in atomic nuclei, recently proposed, is modified and further developed in more detail. It is firstly applied to the light two-cluster $^{20}$ Ne + $α$ system of $^{24}$ Mg, the latter exhibiting well developed low-energy $K^{π} = 0_{1}^{+}$ , $K^{π} = 2_{1}^{+}$ and $K^{π} = 0_{1}^{-}$ rotational bands in its spectrum. A simple algebraic Hamiltonian, consisting of dynamical symmetry, residual and vertical mixing parts is used to describe these three lowest rotational bands of positive and negative parity in $^{24}$ Mg. A good description of the excitation energies is obtain by considering only the $S U (3)$ cluster states restricted to the stretched many-particle Hilbert subspace, built on the leading Pauli allowed $S U (3)$ multiplet for the positive- and negative-parity states, respectively. The coupling to the higher cluster-model configurations allows to describe the known low-lying experimentally observed $B (E 2)$ transition probabilities within and between the cluster states of the three bands under consideration without the use of an effective charge.
nucl-thCommun.Theor.Phys.(2025)·2 citations
03
$^{3}$ He spin-dependent structure functions within the relativistic Light-Front Hamiltonian dynamics
Eleonora Proietti🇮🇹 · Filippo Fornetti🇮🇹 · Emanuele Pace🇮🇹 · Matteo Rinaldi🇮🇹 · Giovanni Salmè🇮🇹 · Sergio Scopetta🇮🇹
$^{3}$ He spin-dependent structure functions, $g_{1}^{3} (x)$ and $g_{2}^{3} (x)$ , which parametrize the hadronic tensor in polarized deep-inelastic scattering, were evaluated within the Poincaré covariant light-front framework. The Bakamjian-Thomas construction of the Poincaré generators allows us to make use of a realistic $^{3}$ He wave function, obtained from refined nuclear phenomenological potentials. The same approach was already successfully applied to the $^{3}$ He and $^{4}$ He unpolarized deep-inelastic scattering. To investigate the neutron polarized structure functions, $g_{1}^{n}$ and $g_{2}^{n}$ , a readily implementable procedure, aimed at extracting the neutron spin structure functions from those of $^{3}$ He, is shown to hold. Moreover, the first moment of $g_{1}^{3} (x)$ was evaluated, aiming at providing a valuable check of the Bjorken sum rule. The present analysis is relevant for experiments nvolving polarized beams planned at the future facilities, like the Electron Ion Colliders.
nucl-thhep-phPRC(2024)·1 citation
04
Evidence for Three- $α$ Breathing Modes Uncovered by Control Neural Network
Zheng Cheng · Mengjiao Lyu · Takayuki Myo · Hisashi Horiuchi · Hiroshi Toki · Zhongzhou Ren · Masahiro Isaka · Mengyun Mao · Hiroki Takemoto · Niu Wan · Wenlong You · Qing Zhao
This work introduces a new Control Neural Network (Ctrl.NN) method to uncover evidence of exotic quantum state, \textit{i.e.}, the breathing modes in 3- $α$ resonant states of $^{12}$ C nucleus. We provide the most precise microscopic description to date for the $^{12}$ C energy spectrum, identify two new exotic breathing states, and uncover strong evidence that directly connects the recent experimental observations to the breathing modes. The Ctrl.NN method significantly simplifies numerical calculations of quantum systems under multiple constraints and offers a new perspective for solving the nuclear many-body problem.
nucl-thPLB(2025)·9 citations
05
Electromagnetic isovector form factors of the transition from the $N^{*} (1520)$ to the nucleon
Di An🇸🇪 · Stefan Leupold🇸🇪
Dispersion theory is used to provide a model-independent low-energy representation of the three electromagnetic isovector transition form factors $N^{*} (1520) \to N$ . At low energies the virtual photon couples dominantly to a pion pair. Taking the very well understood pion vector form factor and pion re-scattering into consideration, the determination of the transition form factors is traced back to the determination of pion-baryon scattering amplitudes. Their low-energy aspects are parametrized by baryon exchange, accounting for the main decay channels of the $N^{*} (1520)$ . Short-distance physics is encoded in subtraction constants that are fitted to data on space-like form factors and hadronic decays. It is shown that a limitation in the determination of the subtraction constants lies in the fact that isovector form factors require sufficient information about the differences between protons and neutrons. In particular, this calls for improvements in the form factor extraction from the electroproduction of the $N^{*} (1520)$ on the neutron. Via the dispersion relations, space- and time-like regions are naturally connected from first principles. This allows to predict the time-like form factors that enter the Dalitz decays $N^{*} (1520) \to N e^{-} e^{+}$ and $N^{*} (1520) \to N μ^{-} μ^{+}$ . Under the assumption of the dominance of the isovector over the isoscalar channel, the Dalitz decay distributions are predicted.
nucl-thhep-ph6 citations
06
Universality of scaled particle spectra in ultrarelativistic heavy-ion collisions
Cicero D. Muncinelli🇧🇷 · Fernando G. Gardim🇧🇷 · David D. Chinellato🇦🇹 · Gabriel S. Denicol🇧🇷 · Andre V. Giannini🇧🇷 · Matthew Luzum🇧🇷 · Jorge Noronha🇺🇸 · Tiago Nunes da Silva🇧🇷 · Jun Takahashi🇧🇷 · Giorgio Torrieri🇧🇷
We study the transverse momentum spectra of identified particles in ultrarelativistic collisions of large and small collision systems. In order to isolate information contained in the momentum dependence, we propose to scale the spectra by the total particle number and mean transverse momentum -- global quantities which are already well studied. We observe an interesting, nearly universal, centrality-independent shape in the scaled spectra, similar to scalings that have been studied previously. This scaling behavior breaks down at large transverse momentum and for very small systems, such as those produced in p-p collisions. We perform hybrid hydrodynamic simulations and show that, in these simulations, a centrality-independent shape is a consequence of an event-by-event independence. Our results motivate further theoretical and experimental investigations of the regime of validity of this scaling phenomenon and their physical interpretation at different collision energies and systems.
nucl-thhep-phPRC(2025)·7 citations
07
Hybrid Star Properties with NJL and MFTQCD Model: A Bayesian Approach
Milena Albino🇵🇹 · Tuhin Malik🇵🇹 · Márcio Ferreira🇵🇹 · Constança Providência🇵🇹
The composition of the core of neutron stars (NS) is still under debate. One possibility is that because of the high densities reached in their cores, matter could be deconfined into quark matter. We investigate the existence of hybrid stars, using microscopic models to describe different phases of matter. Within the adopted microscopic models we calculate properties of NS and properties of matter. We want to probe the pQCD calculations influence and analyze properties that identify a transition to deconfined matter. Bayesian approach is applied to generate 8 sets of equations of state (EOS). A Maxwell construction is adopted to describe the deconfinement transition. For the hadron phase, we consider a stiff and a soft EOS obtained from the Relativistic Mean Field model with nonlinear meson terms. For the quark phase, we use 2 different models: the Nambu-Jona-Lasinio model with multiquark interactions and the Mean Field Theory of QCD, a model similar to the vector MIT bag model. Bayesian inference was applied to determine the model parameters that satisfy the X-ray observations from NICER and have phase transition at densities between 0.15 - 0.40 fm $^{- 3}$ . We also applied restrictions from the pQCD calculations to half of the sets. Hybrid stars are compatible with current observational data. The pQCD restrictions reduce the value of the $M_{ma x}$ . However, even applying this restriction, the models were able to reach values of $2.1 - 2.3 M_{⊙}$ . The conformal limit was still not attained at the center of the most massive stars. The vector interactions are essential to describe hybrid stars with a mass above $2 M_{⊙}$ . The multiquark interactions introduced may affect the limits of some quantities considered as indicators of the presence of a deconfined phase. It is possible to find a set of EOS, that predict that inside NS the renormalized matter trace anomaly is always positive.
nucl-thastro-ph.HEgr-qchep-phPRD(2024)·29 citations
08
Anomalous thresholds in $B \to (P, V) γ^{*}$ form factors
Simon Mutke🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪
We study the effects of anomalous thresholds on the non-local form factors describing the hadronization of the light-quark contribution to $B \to (P, V) γ^{*}$ transitions. Starting from a comprehensive discussion of anomalous thresholds in the triangle loop function for different mass configurations, we detail how the dispersion relation for $π π$ intermediate states is affected by contour deformations mandated by the anomalous branch points. Phenomenological estimates of the size of the anomalous contributions to the form factors are provided with couplings determined from measured branching fractions and Dalitz plot distributions. Our key finding is that anomalous effects are suppressed on the $ρ (770)$ resonance, while off-peak the effects can become as large as $O (10%)$ of the full (light-quark-loop induced) non-local form factors. We comment on future generalizations towards higher intermediate states and the charm loop, outlining how the dispersive framework established in this work could help improve the non-local form factors needed as input for a robust interpretation of $B \to (P, V) ℓ^{+} ℓ^{-}$ decays.
↳ hep-phhep-exnucl-thJHEP(2024)·22 citations
09
Gluon radiation inside a flowing medium
Matvey V. Kuzmin🇷🇺 · Xoán Mayo López🇪🇸
We compute the spectrum of gluons emitted by a highly energetic quark inside a flowing QCD medium, focusing on the soft gluon limit at first order in the opacity expansion. Specifically, we derive the leading energy-suppressed corrections to the double differential final parton distribution, and show that they are substantial for both static and flowing matter. In particular, we demonstrate that the corrections due to the transverse flow become large even at moderate energies and flow velocities, affecting drastically both the shape and magnitude of the spectrum. We observe that the final transverse momentum of the emitted gluon tends to align along the flow direction, resulting in a non-trivial azimuthal distribution. These results can be directly implemented into the estimation of multiple observables to get a better understanding of the jet-medium interaction processes in HICs.
↳ hep-phnucl-thPRD(2026)·17 citations
10
Electric Conductivity of QCD Matter and Dilepton Spectra in Heavy-Ion Collisions
Ralf Rapp🇺🇸
The electric conductivity, $σ_{el}$ , is a fundamental transport coefficient of QCD matter that can be related to the zero-energy limit of the electromagnetic (EM) spectral function at vanishing 3-momentum in the medium. The EM spectral function is also the central quantity to describe the thermal emission rates and pertinent spectra of photon and dilepton radiation in heavy-ion collisions. Employing a model for dilepton rates that combines hadronic many-body theory with nonperturbative QGP emission constrained by lattice-QCD which describes existing dilepton measurements in heavy-ion collisions, we investigate the sensitivity of low-mass dilepton spectra in Pb-Pb collisions at the LHC to $σ_{el}$ . In particular, we disentangle the contributions from QGP and hadronic emission, and identify signatures that can help to extract $σ_{el}$ from high-precision experimental data expected to be attainable with future detector systems at the LHC.
↳ hep-phnucl-exnucl-thPRC(2024)·12 citations
11
Inference of neutron-star properties with unified crust-core equations of state for parameter estimation
P. J. Davis🇫🇷 · H. Dinh Thi🇫🇷 · A. F. Fantina🇫🇷 · F. Gulminelli🇫🇷 · M. Oertel🇫🇷 · L. Suleiman🇫🇷
Relating different global neutron-star (NS) properties, such as tidal deformability and radius, or mass and radius, requires an equation of state (EoS). Determining the NS EoS is therefore not only the science goal of a variety of observational projects, but it also enters in the analysis process; for example, to predict a NS radius from a measured tidal deformability via gravitational waves (GW) during the inspiral of a binary NS merger. To this aim, it is important to estimate the theoretical uncertainties on the EoS, one of which is the possible bias coming from an inconsistent treatment of the low-density region; that is, the use of a so called non-unified NS crust. We propose a numerical tool allowing the user to consistently match a nuclear-physics informed crust to an arbitrary high-density EoS describing the core of the star. We introduce an inversion procedure of the EoS close to saturation density that allows users to extract nuclear-matter parameters and extend the EoS to lower densities in a consistent way. For the treatment of inhomogeneous matter in the crust, a standard approach based on the compressible liquid-drop (CLD) model approach was used in our work. A Bayesian analysis using a parametric agnostic EoS representation in the high-density region is also presented in order to quantify the uncertainties induced by an inconsistent treatment of the crust. We show that the use of a fixed, realistic-but-inconsistent model for the crust causes small but avoidable errors in the estimation of global NS properties and leads to an underestimation of the uncertainties in the inference of NS properties. Our results highlight the importance of employing a consistent EoS in inference schemes. The numerical tool that we developed to reconstruct such a thermodynamically consistent EoS, CUTER, has been tested and validated for use by the astrophysical community.
↳ astro-ph.HEnucl-thAstron.Astrophys.(2024)·39 citations

Affiliations

first authorsco-authorsvia INSPIRE