Nuclear Theory·nucl-th

Tuesday·April 11, 2023

15 papers—8 primary·7 cross-listed

01
Towards $ab$ - $initio$ nuclear theory calculations of $δ_{C}$
Chien-Yeah Seng · Mikhail Gorchtein
We propose a new theory framework to study the isospin-symmetry breaking correction $δ_{C}$ in superallowed nuclear beta decays, crucial for the precise determination of $∣ V_{u d} ∣$ . Based on a general assumptions of the isovector dominance in ISB interactions, we construct a set of functions $F_{T_{z}}$ which involve nuclear matrix elements of isovector monopole operators and the nuclear Green's function. Via the functions $F_{T_{z}}$ , a connection of $δ_{C}$ to measurable electroweak nuclear radii is established, providing an experimental gauge of the theory accuracy of $δ_{C}$ . We outline a strategy to perform ab-initio calculations of $F_{T_{z}}$ based on the Lanczos algorithm, and discuss its similarity with other nuclear-structure-dependent inputs in nuclear beta decays.
nucl-thhep-exhep-lathep-ph+1PRC(2024)·20 citations
02
Collective flows of clusters and pions in heavy-ion collisions at GeV energies
Heng-Jin Liu🇨🇳 · Hui-Gan Cheng🇨🇳 · Zhao-Qing Feng🇨🇳
Within the framework of the quantum molecular dynamics transport model, the collective flows of clusters and pions in heavy-ion collisions have been systematically investigated. The clusters are recognized by the Wigner phase-space density approach at the stage of freeze out in nuclear collisions, i.e., deuteron, triton, $^{3}$ He and $α$ . The directed and elliptic flows of protons and deuterons in the reaction of $^{197}$ Au+ $^{197}$ Au at incident energy 1.23\emph{A} GeV are nicely consistent with the recent HADES data. The higher order collective flows, i.e., triangular and quadrangle flows, manifest the opposite trends with the less amplitude in comparison with the rapidity distributions of directed and elliptic flows. The flow structure of $^{3}$ He and $α$ is very similar to the proton spectra. The influence of the pion potential on the pion production is systematically investigated and compared with the FOPI data via the transverse momentum, longitudinal rapidity and collective flows in collisions of $^{197}$ Au + $^{197}$ Au. It is manifested that the pion yields are slightly suppressed in the domain of mid-rapidity and high momentum. The antiflow phenomena is reduced by implementing the pion potential and more consistent with the FOPI data in collisions of $^{197}$ Au+ $^{197}$ Au at the incident energy 1.5\emph{A} GeV.
nucl-thPRC(2023)·7 citations
03
Bottomonium transport in p-Pb and Pb-Pb collisions at the LHC
Baoyi Chen🇨🇳 · Bo Tong🇨🇳
We employ the Boltzmann transport model to study the sequential suppression pattern of $Υ (1 S, 2 S, 3 S)$ states in both small (p-Pb) and the large (Pb-Pb) collision systems at $s_{N N} = 5.02$ TeV. The cold nuclear matter effects happen before the formation of bottomonium, which is the same for different bottomonium states $Υ (1 S, 2 S, 3 S)$ . The sequential suppression pattern of bottomonium states is treated as a signal of the hot medium effects, where bottomonium states suffer different magnitudes of the color screening and parton inelastic scatterings due to their different geometry sizes and binding energies. Bottomonium excited states are more easily dissociated with smaller binding energy via the final-state interactions. Including both cold and hot medium effects, transport model consistently explains the experimental data about bottomonium in both small and large collision systems.
nucl-thhep-phPRC(2023)·4 citations
04
Study of the heavy quarks energy loss through medium polarization, elastic collision and radiative processes
Jai Prakash🇮🇳 · Mohammad Yousuf Jamal🇮🇳
Heavy quarks serve as crucial probes for exploring the properties of the hot and dense medium formed in heavy-ion collision experiments. Understanding the modification of their energy as they traverse the medium is a focal point of research, with various authors extensively studying this phenomenon. This study specifically concentrates on the equilibrium phase, the quark-gluon plasma, and offers a comparative analysis of heavy quark energy loss through medium polarization, elastic collisions, and radiation. Notably, while previous studies have compared polarization loss and radiation, our work extends this by incorporating elastic collisions for a more comprehensive examination. The significance of medium polarization, particularly at low momentum, is underscored, as it has been found to contribute substantially. The formalism for energy loss and drag coefficient in each case is presented, followed by the calculation of the nuclear modification factor ( $R_{AA}$ ) for a holistic comparative study.
nucl-thhep-phhep-thEur.Phys.J.Plus(2024)·8 citations
05
Systematic study of bremsstrahlung emission in reactions with light nuclei in cluster models
S. P. Maydanyuk (1 and 2) · V. S. Vasilevsky (3) ((1) Wigner Research Centre for Physics, Budapest, Hungary, (2) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine, (3) Bogolyubov Institute for Theoretical Physics, Kyiv, Ukraine)
A new model of bremsstrahlung emission in the scattering of light nuclei is constructed with main focus on strict cluster formulation of nuclear processes. Analysis is performed in frameworks of the folding approximation of the formalism with participation of $s$ -nuclei. Reactions $p$ + $^{4}$ He, $^{2}$ D + $^{4}$ He, $^{3}$ H + $^{4}$ He, $^{3}$ He + $^{4}$ He are included to analysis. Systematic analysis of properties of emission of bremsstrahlung photons in the wide region of kinetic energy of relative motion of two nuclei from 7 to 1000~MeV is performed. Influence of the oscillator length on the calculated spectra of bremsstrahlung emission is analyzed. On the example of $^{3}$ H + $^{4}$ He, dependence of the bremsstrahlung spectra on parameters of nuclear component of interacting potential is established (at first time for the light nuclei). Experimental bremsstrahlung data for the proton-deuteron scattering and proton- $α$ -particle scattering are analyzed on the basis of this model.
nucl-thhep-phnucl-exPRC(2023)·8 citations
06
Spin alignment of vector mesons by glasma fields
Avdhesh Kumar🇹🇼 · Berndt Müller🇺🇸 · Di-Lun Yang🇹🇼
We explain how spin alignment of vector mesons can be induced by background fields, such as electromagnetic fields or soft gluon fields. Our study is based on the quantum kinetic theory of spinning quarks and antiquarks and incorporates the relaxation of the dynamically generated spin polarization. The spin density matrix of vector mesons is obtained by quark coalescence via the Wigner function and kinetic equation. Our approach predicts a local spin correlation that is distinct from the non-local expressions previously obtained in phenomenological derivations. We estimate the magnitude of such local correlations in the glasma model of the preequilibrium phase of relativistic heavy ion collisions. It is found that the resulting spin alignment could be greatly enhanced and may be comparable to the experimental measurement in order of magnitude. We further propose new phenomenological scenarios to qualitatively explain the transverse-momentum and centrality dependence of spin alignment in a self-consistent framework.
nucl-thhep-phPRD(2023)·67 citations
07
Multijet topology in high-energy nuclear collisions: jet broadening
Jin-Wen Kang🇨🇳 · Lei Wang🇨🇳 · Wei Dai🇨🇳 · Sa Wang🇨🇳 · Ben-Wei Zhang🇨🇳
This work presents the first theoretical investigation of the medium modification of jet broadening as an event-shape observable in multijet final states due to jet quenching in high-energy nuclear collisions. The partonic spectrum of $pp$ collisions with next-to-leading order (NLO) accuracy at $s_{NN} = 5.02$ TeV is provided by the POWHEG $+$ PYTHIA8 event generator, while the linear Boltzmann transport (LBT) model is utilized to investigate the energy loss of fast partons as they traverse through the hot and dense QCD medium. We present the jet broadening distributions in multijet final states for both $pp$ and PbPb collisions at $s_{NN} = 5.02$ TeV, then observe an enhancement at the small jet broadening region and suppression at the large jet broadening region in PbPb collisions relative to that in $pp$ . This suggests that medium modification with parton energy loss in the QGP leads to a more concentrated energy flow in all observed multijet events in PbPb reactions. We also demonstrate that the intertwining of two effects, the jet number reduction and the restructured contribution, results in the novel behavior of nuclear modification of the jet broadening observable in PbPb collisions.
nucl-thhep-exhep-phPRC(2025)·6 citations
08
Machine learning one-dimensional spinless trapped fermionic systems with neural-network quantum states
J. W. T. Keeble · M. Drissi · A. Rojo-Francàs · B. Juliá-Díaz · A. Rios
We compute the ground-state properties of fully polarized, trapped, one-dimensional fermionic systems interacting through a gaussian potential. We use an antisymmetric artificial neural network, or neural quantum state, as an ansatz for the wavefunction and use machine learning techniques to variationally minimize the energy of systems from 2 to 6 particles. We provide extensive benchmarks with other many-body methods, including exact diagonalisation and the Hartree-Fock approximation. The neural quantum state provides the best energies across a wide range of interaction strengths. We find very different ground states depending on the sign of the interaction. In the non-perturbative repulsive regime, the system asymptotically reaches crystalline order. In contrast, the strongly attractive regime shows signs of bosonization. The neural quantum state continuously learns these different phases with an almost constant number of parameters and a very modest increase in computational time with the number of particles.
nucl-thcond-mat.quant-gasphysics.comp-phquant-phPRA(2023)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE