Nuclear Theory·nucl-th

Monday·January 23, 2023

6 papers—5 primary·1 cross-listed

01
Collision geometry effect on free spectator nucleons in relativistic heavy-ion collisions
Lu-Meng Liu🇨🇳 · Jun Xu🇨🇳 · Guang-Xiong Peng🇨🇳
Based on the deformed nucleon distributions obtained from the constrained Skyrme-Hartree-Fock-Bogolyubov calculation using different nuclear symmetry energies, we have investigated the effects of the neutron skin and the collision geometry on the yield of free spectator nucleons as well as the yield ratio $N_{n} / N_{p}$ of free spectator neutrons to protons in collisions of deformed nuclei at RHIC energies. We found that tip-tip (body-body) collisions with prolate (oblate) nuclei lead to fewest free spectator nucleons, compared to other collision configurations. While the $N_{n} / N_{p}$ ratio is sensitive to the average neutron-skin thickness of colliding nuclei and the symmetry energy, it is affected by the polar angular distribution of the neutron skin in different collision configurations. We also found that the collision geometry effect can be as large as 50% the symmetry energy effect in some collision systems. Due to the particular deformed neutron skin in $^{238}$ U and $^{96}$ Zr, the symmetry energy effect on the $N_{n} / N_{p}$ ratio is enhanced in tip-tip $^{238}$ U+ $^{238}$ U collisions and body-body $^{96}$ Zr+ $^{96}$ Zr collisions compared to other collision orientations in the same collision system. Our study may shed light on probing deformed neutron skin by selecting desired configurations in high-energy collisions with deformed nuclei.
nucl-thhep-exnucl-exNucl.Phys.Rev.(2023)·6 citations
02
Probing neutron skin and symmetry energy with relativistic isobar collisions
Hao-jie Xu🇨🇳
In these proceedings, we present the three proposed observables to probe the neutron skin and symmetry energy with relativistic isobar collisions, namely, the isobar ratios of the produced hadron multiplicities ( $N_{ch}$ ), the mean transverse momenta ( $⟨ p_{⊥} ⟩$ ), and the net charge multiplicities ( $Δ Q$ ). Our findings suggest potentially significant improvement to neutron skin and symmetry energy determination over traditional low energy methods.
nucl-thnucl-exEPJ Web Conf.(2023)·4 citations
03
Auxiliary field diffusion Monte Carlo calculations of magnetic moments of light nuclei with chiral EFT interactions
J. D. Martin🇺🇸 · S. J. Novario🇺🇸 · D. Lonardoni🇺🇸 · J. Carlson🇺🇸 · S. Gandolfi🇺🇸 · I. Tews🇺🇸
We calculate the magnetic moments of light nuclei ( $A < 20$ ) using the auxiliary field diffusion Monte Carlo method and local two- and three-nucleon forces with electromagnetic currents from chiral effective field theory. For all nuclei under consideration, we also calculate the ground-state energies and charge radii. We generally find a good agreement with experimental values for all of these observables. For the electromagnetic currents, we explore the impact of employing two different power countings, and study theoretical uncertainties stemming from the truncation of the chiral expansion order-by-order for select nuclei within these two approaches. We find that it is crucial to employ consistent power countings for interactions and currents to achieve a systematic order-by-order convergence.
nucl-thPRC(2023)·20 citations
04
Computational budget optimization for Bayesian parameter estimation in heavy ion collisions
Brandon Weiss🇺🇸 · Jean-François Paquet🇺🇸 · Steffen A. Bass🇺🇸
Bayesian parameter estimation provides a systematic approach to compare heavy ion collision models with measurements, leading to constraints on the properties of nuclear matter with proper accounting of experimental and theoretical uncertainties. Aside from statistical and systematic model uncertainties, interpolation uncertainties can also play a role in Bayesian inference, if the model's predictions can only be calculated at a limited set of model parameters. This uncertainty originates from using an emulator to interpolate the model's prediction across a continuous space of parameters. In this work, we study the trade-offs between the emulator (interpolation) and statistical uncertainties. We perform the analysis using spatial eccentricities from the T $_{R}$ ENTo model of initial conditions for nuclear collisions. Given a fixed computational budget, we study the optimal compromise between the number of parameter samples and the number of collisions simulated per parameter sample. For the observables and parameters used in the present study, we find that the best constraints are achieved when the number of parameter samples is slightly smaller than the number of collisions simulated per parameter sample.
nucl-thJ.Phys.G(2023)·6 citations
05
Multiphonon structure of high-spin states in $^{40}$ Ca, $^{90}$ Zr, and $^{208}$ Pb
N. Lyutorovich · V. Tselyaev
The method of description of the high-spin states, which was previously developed and applied for the states of this type in $^{208}$ Pb, is generalized for the case of the states having more complex multiphonon structure. In this method, the harmonic approximation with the renormalized phonons is used in which the phonons themselves are determined within the non-linear version of the model based on the random-phase approximation (RPA) and including both the RPA correlations and the beyond-RPA ones. The mean field and the residual interaction are derived within the framework of the self-consistent RPA from the energy-density functional of the Skyrme type. The method is applied for the analysis of the available experimental data in doubly magic $^{208}$ Pb and $^{40}$ Ca and in semi-magic $^{90}$ Zr.
nucl-thIJMPE(2023)·1 citation
06
Photo-production of lowest $Σ_{1/ 2^{-}}^{*}$ state within the Regge-effective Lagrangian approach
Yun-He Lyu🇨🇳 · Han Zhang🇨🇳 · Neng-Chang Wei🇨🇳 · Bai-Cian Ke🇨🇳 · En Wang🇨🇳 · Ju-Jun Xie🇨🇳
Since the lowest $Σ^{*}$ state, with quantum numbers spin-parity $J^{P} = 1/ 2^{-}$ , is far from established experimentally and theoretically, we have performed a theoretical study on the $Σ_{1/ 2^{-}}^{*}$ photo-production within the Regge-effective Lagrangian approach. Taking into account that the $Σ_{1/ 2^{-}}^{*}$ couples to the $K ˉ N$ channel, we have considered the contributions from the $t$ -channel $K$ exchange diagram. Moreover, these contributions from $t$ -channel $K^{*}$ exchange, $s$ -channel nucleon pole, $u$ -channel $Σ$ exchange, and the contact term, are considered. The differential and total cross sections of the process $γ n \to K^{+} Σ_{1/ 2^{-}}^{*-}$ are predicted with our model parameters. The results should be helpful to search for the $Σ_{1/ 2^{-}}^{*}$ state experimentally in future.
↳ hep-phnucl-thCPC(2023)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

Collision geometry effect on free spectator nucleons in relativistic heavy-ion collisions

Probing neutron skin and symmetry energy with relativistic isobar collisions

Auxiliary field diffusion Monte Carlo calculations of magnetic moments of light nuclei with chiral EFT interactions

Computational budget optimization for Bayesian parameter estimation in heavy ion collisions

Multiphonon structure of high-spin states in 40Ca, 90Zr, and 208Pb

Photo-production of lowest Σ1/2−∗​ state within the Regge-effective Lagrangian approach

Affiliations

Multiphonon structure of high-spin states in $^{40}$ Ca, $^{90}$ Zr, and $^{208}$ Pb

Photo-production of lowest $Σ_{1/ 2^{-}}^{*}$ state within the Regge-effective Lagrangian approach