Nuclear Theory·nucl-th

Mon·Feb 24, 2025Monday·February 24, 2025

7 papers—4 primary·3 cross-listed

01
Hypernuclear cluster states of $_{Λ}^{12} B$ Unveiled through Neural Network-Driven Microscopic Calculation
Jiaqi Tian🇨🇳 · Mengjiao Lyu🇨🇳 · Zheng Cheng🇨🇳 · Masahiro Isaka🇯🇵 · Akinobu Dote🇯🇵 · Takayuki Myo🇯🇵 · Hisashi Horiuchi🇯🇵 · Hiroki Takemoto🇯🇵 · Niu Wan🇨🇳 · Qing Zhao🇨🇳
We investigate the hypernuclear cluster states of $_{Λ}^{12} B$ using a neural-network-driven microscopic model. We extend the Control Neural Networks (Ctrl.NN) method and systematically calculate the positive-parity spectrum of $_{Λ}^{12} B$ . By incorporating $s d$ -shell excitations and parity-coupling effects into the $_{Λ}^{12} B$ hypernuclear system, we reveal structural changes, including clustering effects and new configurations such as isosceles-triangle and $α$ - $t$ - $α$ linear-chain structures. Furthermore, by comparing with experimental data, we identify that many peaks ( $#$ 6 and $#$ 8) can be interpreted as $p_{Λ}$ dominant states, which is consistent with shell-model predictions. Notably, based on our analysis of the excited states of $_{Λ}^{12} B$ , we propose possible candidates for previously unexplained or controversial experimental peaks.
nucl-thPLB(2025)·9 citations
02
Kubo formulas for spin polarization in dissipative relativistic spin hydrodynamics: a first-order gradient expansion approach
Matteo Buzzegoli (West University of Timisoara)🇷🇴
We use linear response theory to derive both the non-dissipative and dissipative effects of spin polarization for massive and massless interacting spin 1/2 particles in a relativistic fluid. We list and classify all the possible contributions up to first order in gradients of hydrodynamic fields including the axial chemical potential and the spin potential, and we obtain the corresponding Kubo formulas. We find that all the possible dissipative contributions, except those coming from the gradients of spin potential, require a chiral imbalance or parity violating interactions. In a fluid with chiral imbalance we find a chiral version of the spin Hall effect, i.e. a spin polarization is induced by the gradients of temperature and of axial chemical potential in the direction orthogonal to the momentum of the particle and to the gradients. Moreover, we identify several other new non-dissipative contributions that are not present for free fields.
nucl-thJHEP(2025)·9 citations
03
Examination of the multiple-scattering expansion in the four-nucleon system
A. Deltuva🇱🇹
The elastic neutron- $^{3} H$ scattering at intermediate energies is studied using rigorous integral equations solved in the momentum-space partial-wave basis. The four-particle transition operators are expanded into multiple-scattering series in terms of subsystem transition operators. Various approximations resulting from truncation of the series in different ways are evaluated and their validity is investigated. They fail at lower energies but at higher energies provide a rough reproduction of exact results at small scattering angles. In the large-angle region all approximations fail heavily, indicating that the scattering amplitude results from a delicate interplay of many multiple-scattering terms. The partial-wave analysis reveals that the developed approximations are reliable in higher partial waves, and for practical calculations an efficient ``hybrid'' approach is proposed, combining exact amplitudes in lower partial waves with approximations in higher partial waves. The implications for often used approximation of the first order in two-body transition matrix and development of microscopic optical potentials are discussed.
nucl-thnucl-exPRC(2025)·0 citations
04
Projective Imaging of High-Energy Nuclei via Coherent Exclusive Vector Meson Production in Electron-Nucleus Collisions
Maci Kesler🇺🇸 · Ashik Ikbal Sheikh🇺🇸 · Rongrong Ma🇺🇸 · Zhoudunming Tu🇺🇸 · Thomas Ullrich🇺🇸 · Zhangbu Xu🇺🇸
One of the major goals of modern nuclear experiments is to study the distributions of gluons inside nuclei at high energy. A key measurement is the coherent exclusive vector meson (VM) production in diffractive electron-nucleus collisions, where the gluon spatial distribution inside the nucleus can be obtained through a Fourier transform of the squared nuclear momentum transfer ( $∣ t ∣$ ) distribution. This research aims to overcome the two main obstacles of the $∣ t ∣$ measurement: limited precision in measuring $∣ t ∣$ arising from the momentum resolution of the outgoing electron and the overwhelming incoherent background. We demonstrate that by measuring the projected $∣ t ∣$ distribution along the direction perpendicular to the electron scattering plane, the effect of the outgoing electron's momentum resolution can be effectively mitigated, and the diffractive pattern is largely restored. Furthermore, we propose to measure the angular distribution of the VM's decay daughters to statistically remove the incoherent background.
nucl-thhep-phnucl-exPLB(2026)·8 citations
05
Practical parametrization of two-pole structure
J.X. Cui🇨🇳 · Zhi-Yong Zhou🇨🇳 · Zhiguang Xiao🇨🇳
We suggest that the extended Lee-Friedrichs model could be directly used as a practical parametrization method for the experimental analysis of resonance structures. This parametrization incorporates the constraints of relativistic phase space and the threshold behavior, and respects both unitarity and analyticity constraints of the scattering amplitude. As such, the poles on unphysical Riemann sheets could be easily extracted. This parametrization method offers a comparable fit quality to the improved Breit-Wigner parametrization with an energy-dependent width function when the coupling strength is moderate. It is found that the parametrization could be used to correctly extract the poles near the physical region correctly. In particular, it can naturally incorporate the two-pole structure in which one pole is shifted from the discrete state and the other is dynamically generated. Moreover, the coupled-channel formulation of the extended Lee-Friedrichs parameterization is straightforward and its relationship with the Flatté parametrization form is discussed. Using $ρ (770)$ , $Δ (1232)$ , $K_{0}^{*}$ and $f_{0}$ states as illustrative examples, we demonstrate the effectiveness of this parametrization in capturing fit qualities and identifying relevant poles. It is illustrated that the $K_{0}^{*} (700)$ and $K_{0}^{*} (1430)$ could be perfectly parameterized in the Lee-Friedrichs form as a two-pole structure. A tentative investigation of $f_{0}$ s in coupled-channel parametrization form are discussed, and a possible lineshape contributed by $χ_{c 1} (3872)$ and $χ_{c 1} (4012)$ is presented. The proposed parametrization scheme holds promise for future studies involving exotic hadron states near thresholds, offering a valuable tool for analyzing resonance structures in upcoming experimental investigations.
↳ hep-phhep-exnucl-th1 citation
06
Bounds on variations of the strange quark mass from Big Bang nucleosynthesis
Ulf-G. Meißner🇩🇪 · Bernard Metsch🇩🇪 · Helen Meyer🇩🇪
We analyze the effect of a variation of the strange nucleon matrix element $⟨ N ∣ m_{s} s ˉ s ∣ N ⟩$ on the abundances of the light elements produced in the Big Bang. For that, we vary the nucleon mass in the leading eight reactions that involve neutrons, protons and the four lightest nuclei. We use various available Big Bang nucleosynthesis codes and find that the measured deuterium and $^{4}$ He abundances set strict limits on the nucleon mass variations. This translates into an upper bound of possible variations of the strange quark mass, $∣ Δ m_{s} / m_{s} ∣ \leq 5.1%$ .
↳ hep-phastro-ph.COhep-lathep-th+1JHEP(2025)·2 citations
07
Status of two-baryon scattering in lattice QCD
Jeremy R. Green🇩🇪
In these proceedings, I will review lattice QCD calculations of baryon-baryon scattering, their methods, and their challenges. In the last few years, there has been a new generation of calculations with increased focus on controlling systematic uncertainties. Contrary to the findings of earlier exploratory calculations, it now appears probable that at heavy pion masses there is no nucleon-nucleon bound state.
↳ hep-latnucl-thPoS(2026)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hypernuclear cluster states of Λ12​B Unveiled through Neural Network-Driven Microscopic Calculation

Kubo formulas for spin polarization in dissipative relativistic spin hydrodynamics: a first-order gradient expansion approach

Examination of the multiple-scattering expansion in the four-nucleon system

Projective Imaging of High-Energy Nuclei via Coherent Exclusive Vector Meson Production in Electron-Nucleus Collisions

Practical parametrization of two-pole structure

Bounds on variations of the strange quark mass from Big Bang nucleosynthesis

Status of two-baryon scattering in lattice QCD

Affiliations

Hypernuclear cluster states of $_{Λ}^{12} B$ Unveiled through Neural Network-Driven Microscopic Calculation