Nuclear Theory·nucl-th

Thursday·August 17, 2023

11 papers—5 primary·6 cross-listed

01
Thermodynamics of quark matter with multiquark clusters in an effective Beth-Uhlenbeck type approach
D. Blaschke🇵🇱 · M. Cierniak🇵🇱 · O. Ivanytskyi🇵🇱 · G. Röpke🇵🇱
We describe multiquark clusters in quark matter within a Beth-Uhlenbeck approach in a background gluon field coupled to the underlying chiral quark dynamics using the Polyakov gauge which establishes the center symmetry of color SU(3) that suppresses colored states as an aspect of confinement. Quark confinement is modeled by a large quark mass in vacuum motivated by a confining density functional approach. A multiquark cluster containing $n$ quarks and antiquarks is described as a binary composite of smaller subclusters $n_{1}$ and $n_{2}$ ( $n_{1} + n_{2} = n$ ). It has a spectrum consisting of a bound state and a scattering state continuum. For the corresponding cluster-cluster phase shifts we discuss simple ansätze that capture the Mott dissociation of clusters as a function of temperature and chemical potential. We go beyond the simple "step-up-step-down" model that ignores continuum correlations and introduce an improved model that includes them in a generic form. In order to explain the model, we restrict ourselves here to the cases where the cluster size is $1 \leq n \leq 6$ . A striking result is the suppression of the abundance of colored multiquark clusters at low temperatures by the coupling to the Polyakov loop and their importance for a quantitative description of lattice QCD thermodynamics at non-vanishing baryochemical potentials. An important ingredient are Polyakov-loop generalized distribution functions of $n$ -quark clusters which are derived here for the first time. Within our approach we calculate thermodynamic properties such as baryon density and entropy. We demonstrate that the limits of a hadron resonance gas at low temperatures and $O (g^{2})$ perturbative QCD at high temperatures are correctly reproduced. A comparison with lattice calculations shows that our model is able to give a unified, systematic approach to describe properties of the quark-gluon-hadron system.
nucl-thhep-phEPJA(2024)·11 citations
02
Radial Oscillations of Neutron Stars with Antikaon Condensate
Apurba Kheto🇮🇳 · Prasanta Char🇧🇪
In this article, we study the neutron stars with antikaon condensates and their radial oscillations. We incorporate the antikaons $(K^{-}, K ˉ^{0})$ within a relativistic mean field theory with density dependent couplings. A transition to the kaon condensed phase is treated as a second order phase transition for different possible antikaon optical potentials. Then, we solve the structure equations of stars and calculate the fundamental and higher order frequencies of their radial pulsations. We study the eigenfunctions of different radial modes for a $2 M_{⊙}$ star with equations of state having different potential depths of antikaons. We also study the large frequency separations for the $2 M_{⊙}$ star. We find distinct features of the appearances of antikaons on the eigenfunctions. The shape of the eigenfunctions corresponding to the radial perturbations is affected due to the appearance of the antikaons, but for the pressure perturbation, the shape remains unchanged.
nucl-thastro-ph.HEEPJA(2023)·5 citations
03
Constraints on the Nuclear Symmetry Energy from Experiments, Theory and Observations
James M. Lattimer
Nuclear mass measurements and neutron matter theory tightly constrain the nuclear symmetry energy parameters $J$ , $L$ , $K_{sy m}$ and $Q_{sy m}$ . Corroboration of these constraints on $J$ and $L$ can be found from measurements of the neutron skin thicknesses and dipole polarizabilities of neutron-rich nuclei. The experimental constraints on these parameters are compared with those obtained from consideration of astrophysical measurements of the neutron star radius, which we show is highly correlated with $L$ . Attention is aimed at the recent PREX and CREX neutron skin measurements from Jefferson Lab, NICER neutron star radius measurements, and a new interpretation of the GW170817 tidal deformability measurement. We find joint satisfaction of PREX and CREX gives $J = 32.2 \pm 1.7$ MeV and $L = 52.9 \pm 13.2$ MeV, in excellent agreement with neutron matter predictions of $J = 32.0 \pm 1.1$ MeV and $L = 51.9 \pm 7.9$ MeV.
nucl-thastro-ph.HEnucl-exJ.Phys.Conf.Ser.(2023)·16 citations
04
Elastic scattering and total reaction cross sections of $^{6}$ Li studied with a microscopic continuum discretized coupled channels model
Wendi Chen · D.Y. Pang · Hairui Guo · Ye Tao · Weili Sun · Yangjun Ying
We present a systematic study of $^{6}$ Li elastic scattering and total reaction cross sections at incident energies around the Coulomb barrier within the continuum discretized coupled-channels (CDCC) framework, where $^{6}$ Li is treated in an $α$ + $d$ two-body model. Collisions with $^{27}$ Al, $^{64}$ Zn, $^{138}$ Ba and $^{208}$ Pa are analyzed. The microscopic optical potentials (MOP) based on Skyrme nucleon-nucleon interaction for $α$ and $d$ are adopted in CDCC calculations and satisfactory agreement with the experimental data is obtained without any adjustment on MOPs. For comparison, the $α$ and $d$ global phenomenological optical potentials (GOP) are also used in CDCC analysis and a reduction no less than 50 $%$ on the surface imaginary part of deuteron GOP is required for describing the data. In all cases, the $^{6}$ Li breakup effect is significant and provides repulsive correction to the folding model potential. The reduction on the surface imaginary part of GOP of deuteron reveals a strong suppression of the reaction probability of deuteron as a component of $^{6}$ Li as compared with that of a free deuteron. A further investigation is made by taking the $d$ breakup process into account equivalently within the dynamic polarization potential approach and it shows that $d$ behaves like a tightly bound nucleus in $^{6}$ Li induced reactions.
nucl-thCPC(2024)·1 citation
05
Effect of Spin-Dependent Short-Range Correlations on Nuclear Matrix Elements for Neutrinoless Double Beta Decay of $^{48}$ Ca
S.Sarkar🇮🇳 · Y. Iwata🇯🇵
The neutrinoless double beta decay is a pivotal weak nuclear process that holds the potential to unveil the Majorana nature of neutrinos and predict their absolute masses. In this study, we delve into examining the impact of spin-dependent short-range correlations (SRC) on the nuclear matrix elements (NMEs) for the light neutrino-exchange mechanism in neutrinoless double beta ( $0 ν β β$ ) decay of $^{48}$ Ca, employing an extensive interacting nuclear shell model. All computations are performed employing the effective shell model Hamiltonian GXPF1A, encompassing the entire $f p$ model space through the closure approximation. Our investigation examines the NMEs' dependencies on factors such as the number of intermediate states, coupled spin-parity attributes of neutrons and protons, neutrino momentum, inter-nucleon separation, and closure energy. This scrutiny is performed with respect to both the conventional Jastrow-type approach of SRC, employing various parameterizations, and the spin-dependent SRC paradigm. Our findings illuminate a discernible distinction in NMEs induced by spin-dependent SRC, differing by approximately 10-20\% from those computed through the conventional Jastrow-type SRC, incorporating distinct parameterizations.
nucl-thUniverse(2023)·4 citations
06
$X (3960)$ , $X_{0} (4140)$ , and other compact $cs c ˉ s ˉ$ states
Shi-Yuan Li🇨🇳 · Yan-Rui Liu🇨🇳 · Zi-Long Man🇨🇳 · Zong-Guo Si🇨🇳 · Jing Wu🇨🇳
We study the spectrum and rearrangement decays of S-wave $cs c ˉ s ˉ$ tetraquark states in a simplified quark model. The masses and widths are estimated by assuming that the $X (4140)$ is the lower $1^{++}$ $cs c ˉ s ˉ$ tetraquark. Comparing our results with experimental measurements, we find that the recently observed $X (3960)$ by LHCb can be assigned as the lowest $0^{++}$ $cs c ˉ s ˉ$ tetraquark state and the $X_{0} (4140)$ could be the second lowest $0^{++}$ $cs c ˉ s ˉ$ tetraquark. Predictions of ratios between partial widths for the involved tetraquarks are given. We call for searches for more $cs c ˉ s ˉ$ tetraquarks with $J^{P C} = 1^{+-}$ , $0^{++}$ , and $2^{++}$ .
↳ hep-phhep-exhep-latnucl-ex+1CPC(2024)·10 citations
07
The spin alignment of vector mesons with light front quarks
Baochi Fu🇨🇳 · Fei Gao🇨🇳 · Yuxin Liu🇨🇳 · Huichao Song🇨🇳
The global spin alignment of the vector meson has been observed in relativistic heavy ion collisions, but is still on hot debates in the theoretical community. Here we propose to apply the light front framework to explain this phenomenon since the light front form explicitly describes the hadron spin including both the quark spin and the orbital angular momentum. After applying the light front spinor, we find that the spin alignment in the polarization of vector mesons with $ρ_{00} > 1/3$ can be naturally manifested and in particular, the obtained spin alignment for $ϕ$ meson is in good agreement with the experimental data. This implies that to explain the spin alignment it is important to properly include the contribution from the gluon interactions that are presented in terms of the orbital angular momentum of the hadron bound state.
↳ hep-phhep-exnucl-thPLB(2024)·13 citations
08
Complete $N_{f}^{2}$ contributions to four-loop pure-singlet splitting functions
Thomas Gehrmann🇨🇭 · Andreas von Manteuffel🇩🇪 · Vasily Sotnikov🇨🇭 · Tong-Zhi Yang🇨🇭
The scale evolution of parton distributions is determined by universal splitting functions. As a milestone towards the computation of these functions to four-loop order in QCD, we compute all contributions to the pure-singlet quark-quark splitting functions that involve two closed fermion loops. The splitting functions are extracted from the pole terms of off-shell operator matrix elements, and the workflow for their calculation is outlined. We reproduce known results for the non-singlet four-loop splitting functions and validate our new pure-singlet results against fixed Mellin moments.
↳ hep-phhep-thnucl-thJHEP(2024)·49 citations
09
Chiral kinetic theory with self-energy corrections and neutrino spin Hall effect
Naoki Yamamoto🇯🇵 · Di-Lun Yang🇹🇼
We systematically derive the chiral kinetic theory for chiral fermions with collisions, including the self-energy corrections, from quantum field theories. We find that the Wigner functions and chiral kinetic equations receive both the classical and quantum corrections from the self-energies and their spacetime gradients. We also apply this formalism to study nonequilibrium neutrino transport due to the interaction with thermalized electrons and nucleons, as realized in core-collapse supernovae. We derive neutrino currents along magnetic fields and neutrino spin Hall effect induced by the density gradient at first order in the Fermi constant $G_{F}$ for anisotropic neutrino distributions.
↳ hep-phastro-ph.HEnucl-thPRD(2024)·12 citations
10
Generalized parton distributions of gluon in proton: a light-front quantization approach
Bolang Lin🇨🇳 · Sreeraj Nair🇨🇳 · Siqi Xu🇨🇳 · Zhi Hu🇨🇳 · Chandan Mondal🇨🇳 · Xingbo Zhao🇨🇳 · James P.Vary🇺🇸
We solve for the gluon generalized parton distributions (GPDs) inside the proton, focusing specifically on leading twist chiral-even GPDs. We obtain and employ the light-front wavefunctions (LFWFs) of the proton from a light-front quantized Hamiltonian with Quantum Chromodynamics input using basis light-front quantization (BLFQ). Our investigation incorporates the valence Fock sector with three constituent quarks and an additional Fock sector, encompassing three quarks and a dynamical gluon. We examine the GPDs within impact parameter space and evaluate the $x$ -dependence of the transverse square radius. We find that the transverse size of the gluon at lower- $x$ is larger than that of the quark, while it exhibits opposite behavior at large- $x$ . Using the proton spin sum rule, we also determine the relative contributions of quarks and the gluon to the total angular momentum of the proton.
↳ hep-phnucl-thPLB(2023)·32 citations
11
X-PSI Parameter Recovery for Temperature Map Configurations Inspired by PSR J0030+0451
Serena Vinciguerra · Tuomo Salmi · Anna L. Watts · Devarshi Choudhury · Yves Kini · Thomas E. Riley
In the last few years, the NICER collaboration has provided mass and radius inferences, via pulse profile modeling, for two pulsars: PSR J0030+0451 and PSR J0740+6620. Given the importance of these results for constraining the equation of state of dense nuclear matter, it is crucial to validate them and test their robustness. We therefore explore the reliability of these results and their sensitivity to analysis settings and random processes, including noise, focusing on the specific case of PSR J0030+0451. We use X-PSI, one of the two main analysis pipelines currently employed by the NICER collaboration for mass and radius inferences. With synthetic data that mimic the PSR J0030+0451 NICER data set, we evaluate the recovery performances of X-PSI under conditions never tested before, including complex modeling of the thermally emitting neutron star surface. For the test cases explored, our results suggest that X-PSI is capable of recovering the true mass and radius within reasonable credible intervals. This work also reveals the main vulnerabilities of the analysis: a significant dependence on noise and the presence of multi-modal structure in the posterior surface. Noise particularly impacts our sensitivity to the analysis settings and widths of the posterior distributions. The multi-modal structure in the posterior suggests that biases could be present if the analysis is unable to exhaustively explore the parameter space. Convergence testing, to ensure an adequate coverage of the parameter space and a suitable representation of the posterior distribution, is one possible solution to these challenges.
↳ astro-ph.HEastro-ph.SRnucl-thApJ(2023)·27 citations

Affiliations

first authorsco-authorsvia INSPIRE