Nuclear Theory·nucl-th

Thursday·March 7, 2024

11 papers—4 primary·7 cross-listed

01
QCD critical point and hydrodynamic fluctuations in relativistic fluids
Mikhail Stephanov
These lecture notes consist of two major connected parts. The first part (Sections 1, 2), after a brief historical introduction, deals with the physics of critical points in thermodynamic equilibrium. The features of the fluctuations relevant for the QCD critical point search are highlighted. The second part (Sections 3, 4) focuses on the recent developments in the description of the fluctuation dynamics especially relevant for the QCD critical point search in heavy-ion collisions.
nucl-thcond-mat.stat-mechhep-phActa Phys.Polon.B(2024)·5 citations
02
Microscopic description of hexadecapole collectivity in even-even rare-earth nuclei near $N = 90$
L. Lotina · K. Nomura
We present an extensive study of hexadecapole correlations in the rare-earth region near $N = 90$ and the effects these correlations have on various nuclear properties, such as the low-energy spectra, as well as quadrupole, hexadecapole, and monopole transition strengths. In order to examine hexadecapole correlations, we employ a mapped $s d g$ interacting boson model, with parameters derived from a self-consistent mean-field calculations with a relativistic energy density functional. We apply this model to even-even isotopes of Nd, Sm, Gd, Dy, and Er ( $Z = 60 - 68$ ) with neutron numbers $N = 84 - 96$ . The obtained results show a good agreement with the experiment. By comparing the results with the ones obtained from a simpler mapped $s d$ interacting boson model, we show that the inclusion of the hexadecapole degree of freedom via $g$ boson is necessary to improve the results of the $J^{π} \geq 6^{+}$ yrast energies in the nuclei with $N = 84$ and 86, being near the neutron shell closure. The $s d g$ interacting boson model increases the quadrupole transition strengths between yrast states in the $N = 90$ and 92 well deformed nuclei, which is in good agreement with the experiment for most of those isotopes. The presence of $g$ bosons does have an important effect on hexadecapole transition strengths, although experimental data for such transitions are limited. The obtained monopole transition strengths do not differ significantly from the ones obtained from the simpler $s d$ model.
nucl-thnucl-exPRC(2024)·9 citations
03
Controlling volume fluctuations for studies of critical phenomena in nuclear collisions
Romain Holzmann🇩🇪 · Volker Koch🇺🇸 · Anar Rustamov🇩🇪 · Joachim Stroth🇩🇪
We generalize and extend the recently proposed method to account for contributions of system size (or volume/participant) fluctuations to the experimentally measured moments of particle multiplicity distributions. We find that in the general case there are additional biases which are not directly accessible to experiment. These biases are, however, parametrically suppressed if the multiplicity of the particles of interest is small compared to the total charged-particle multiplicity, e.g., in the case of proton number fluctuations at top RHIC and LHC energies. They are also small if the multiplicity distribution of charged particles per wounded nucleon is close to the Poissonian limit, which is the case at low energy nuclear collisions, e.g., at GSI/SIS18. We further find that mixed events are not necessarily needed to extract the correction for volume fluctuations, albeit it can help if event statistics is small, which is typically the case for reconstructing the higher-order cumulants. We provide the formulas to correct pure and mixed cumulants of particle multiplicity distributions up to any order together with their associated biases.
nucl-thhep-exhep-phnucl-exNPA(2024)·16 citations
04
Nuclear magnetism in the deformed halo nucleus $^{31}$ Ne
Cong Pan · Kaiyuan Zhang · Shuangquan Zhang
Based on the point-coupling density functional, the time-odd deformed relativistic Hartree-Bogoliubov theory in continuum (TODRHBc) is developed. Then the effects of nuclear magnetism on halo phenomenon are explored by taking the experimentally suggested deformed halo nucleus $^{31}$ Ne as an example. For $^{31}$ Ne, nuclear magnetism contributes 0.09 MeV to total binding energy, and the breaking of Kramers degeneracy results in 0-0.2 MeV splitting in canonical single-particle spectra. The blocked neutron level has a dominant component of $p$ wave and it is marginally bound. However, if we ignore nuclear magnetism, the level becomes unbound. This shows a subtle mechanism that nuclear magnetism changes the single-particle energies, causing a nucleus to become bound. Based on the TODRHBc results, a prolate one-neutron halo is formed around the near-spherical core in $^{31}$ Ne. The nucleon current is mostly contributed by the halo rather than the core, except near the center of the nucleus. A layered structure in the neutron current distribution is observed and studied in detail.
nucl-thPLB(2024)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE

QCD critical point and hydrodynamic fluctuations in relativistic fluids

Microscopic description of hexadecapole collectivity in even-even rare-earth nuclei near N=90

Controlling volume fluctuations for studies of critical phenomena in nuclear collisions

Nuclear magnetism in the deformed halo nucleus 31Ne

Affiliations

Microscopic description of hexadecapole collectivity in even-even rare-earth nuclei near $N = 90$

Nuclear magnetism in the deformed halo nucleus $^{31}$ Ne