Nuclear Theory·nucl-th

Friday·October 24, 2025

7 papers—4 primary·3 cross-listed

01
[Submitted on 22 Oct 2025]
Computing nuclear response functions with time-dependent coupled-cluster theory
Francesca Bonaiti🇺🇸 · Cody Balos🇺🇸 · Kyle Godbey🇺🇸 · Gaute Hagen🇺🇸 · Thomas Papenbrock🇺🇸 · Carol S. Woodward🇺🇸
We compute nuclear response functions by solving the time-dependent A-body Schrödinger equation, recording the time-dependent transition moment and extracting spectral information via Fourier transforms. The solution of the time-dependent many-body problem accounts for correlations on top of the mean field by taking advantage of a time-dependent formulation of coupled-cluster theory. As a validation, we focus on electric dipole transitions in $^{4}$ He and $^{16}$ O and compare moments of the response function distribution to the results of an equivalent static framework, finding negligible discrepancies. We investigate how proton and neutron densities evolve in time, and we see the traditional picture of soft and giant dipole resonances as collective oscillations of protons and neutrons emerging from our calculations in $^{16}$ O and $^{24}$ O. This method also allows us to investigate the behavior of the nucleus in the presence of a strong electric field. In that regime, the behavior of the system becomes chaotic. Qualitatively, the spectral information obtained in this limit is in line with previous time-dependent mean-field results.
Comments:
16 pages, 15 figures, 2 movies (attached in TeX source), matches published version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2510.19940 [pdf]
PRC(2026)·4 citations
02
[Submitted on 22 Oct 2025]
Nuclear Fragmentation at the Future Electron-Ion Collider
Carlos A. Bertulani🇺🇸
We investigate aspects of low-energy nuclear reactions that could be explored at the forthcoming Electron-Ion Collider (EIC) at Brookhaven National Laboratory and compare them with analogous measurements performed in ultraperipheral collisions (UPCs) at the Large Hadron Collider (LHC) at CERN. The estimated fragmentation cross sections at the EIC are roughly three orders of magnitude smaller than those observed at the LHC. At the LHC, uranium nucleus fragmentation exhibits a distinctive double-peaked mass spectrum arising from fission processes, whereas at the EIC, the breakup pattern is mainly characterized by neutron evaporation and a vastly reduced yield of fission fragments, about four orders of magnitude fewer events in comparison.
Comments:
4 pages, Proceedings of the 29th International Nuclear Physics Conference (INPC 2025), May 25-30, 2025, Daejeon, South Korea
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2510.20014 [pdf]
EPJ Web Conf.(2026)·0 citations
03
[Submitted on 23 Oct 2025]
Probing Neutron Skin through Event-by-Event Pion Asymmetry in Heavy-ion collisions
Xu-Hua Tian🇨🇳 · Long-Gang Pang🇨🇳
In this work, we propose a novel approach for probing the neutron skin thickness of gold (Au) by analyzing the event-by-event distribution of $π^{-}$ and $π^{+}$ yield differences. This is achieved through SMASH simulations of ultra-peripheral Au+Au collisions at $s_{NN} = 3$ GeV. Our results demonstrate that the mean value of $Δ n_{π} = n_{π^{-}} - n_{π^{+}}$ , along with the Pearson correlation and mutual information between $(π^{-} + π^{+})$ and $(π^{-} - π^{+})$ , all scale linearly with the neutron skin thickness. Moreover, the slope of the line connecting two distinct $Δ n_{π}$ values in the event-by-event distribution also exhibits a linear dependence on the neutron skin thickness. The most sensitive $Δ n_{π}$ pairs are identified as $(- 1, 1)$ , $(- 1, 2)$ , $(0, 1)$ , and $(0, 2)$ . These findings establish a new pathway for determining the neutron skin thickness. Finally, by comparing SMASH and UrQMD simulations under identical initial conditions, we observe that individual slope values depend on the specific collision model. However, by extracting slopes from multiple $Δ n_{π}$ pairs in experimental event-by-event data and inferring the corresponding neutron skin thickness, one can assess which model better aligns with the true physical value.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
2510.20166 [pdf]
1 citation
04
[Submitted on 23 Oct 2025]
Data-driven exploration of the neutron $^{3} P_{2}$ pairing gap using Cassiopeia A neutron star observational data: Direct $χ^{2}$ minimization
Yoonhak Nam🇯🇵 · Kazuyuki Sekizawa🇯🇵
The rapid cooling observed in the Cassiopeia~A neutron star (Cas~A NS) is one of the most stringent tests for neutron-star cooling theory. While Cooper-pair breaking and formation (PBF) neutrino emission is a leading candidate, uncertainties remain regarding the PBF efficiency factor $q$ and the neutron $^{3} P_{2}$ pairing gap. This work explores in a data-driven manner how the optimized gap shape responds to variations of the PBF emissivity parameter $q$ within a fixed cooling setup. We introduce a novel gap parametrization, in which each parameter carries direct physical meaning and controls the gap amplitude, peak location, width, and asymmetry. Using a Fortran-based cooling code and the BSk24 equation of state, we perform parameter-space exploration guided by the Cas~A NS data. Global optimization is carried out with Optuna's tree-structured Parzen estimator, followed by local refinement using the Nelder--Mead method. The optimized solutions yield physically reasonable gaps with peak amplitudes $Δ_{m a x} \approx 0.5$ -- $0.6 MeV$ . Although the multi-objective formulation explores the parameter space more broadly, the single-objective $χ^{2}$ -only optimization achieves the lowest $χ^{2}$ . For $M_{NS} = 1.4 M_{⊙}$ , increasing $q$ drives the optimized gap and critical-temperature profiles toward smoother and more localized shapes, improving consistency with the observed trend. Models with $q ≳ 0.4$ reproduce the decline rate within the $1 σ$ confidence interval, whereas the baseline case $q ≃ 0.19$ lies near the $3 σ$ level. Our results suggest larger effective PBF emissivities than the baseline estimate, although robust constraints on $q$ require future Bayesian inference including uncertainties in mass, envelope composition, equation of state, pairing microphysics, and age offset. (Shortened due to the arXiv abstract length limit.)
Comments:
19 pages, 13 figures, 3 tables; v2 - Version accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas)
arXiv:
2510.20353 [pdf]
PRC(2026)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Computing nuclear response functions with time-dependent coupled-cluster theory

Nuclear Fragmentation at the Future Electron-Ion Collider

Probing Neutron Skin through Event-by-Event Pion Asymmetry in Heavy-ion collisions

Data-driven exploration of the neutron 3P2​ pairing gap using Cassiopeia A neutron star observational data: Direct χ2 minimization

Affiliations

Data-driven exploration of the neutron $^{3} P_{2}$ pairing gap using Cassiopeia A neutron star observational data: Direct $χ^{2}$ minimization