Nuclear Theory·nucl-th

Friday·May 29, 2026

9 papers—6 primary·3 cross-listed

01
[Submitted on 28 May 2026]
Bayesian constraints on the transport coefficients $η / s$ and $ζ / s$ from spin polarization in relativisitic heavy-ion collisions
Sushant K. Singh🇮🇹 · Eduardo Grossi🇮🇹 · Francesco Becattini🇮🇹
Bayesian analyses in the context of relativistic heavy-ion collisions have so far relied almost exclusively on bulk hadronic observables constructed from momentum degrees of freedom to constrain the transport properties of the quark-gluon plasma. In this work, we perform the Bayesian inference after incorporating the longitudinal spin polarization of $Λ$ hyperons alongside conventional bulk measurements in Pb+Pb collisions at $s_{N N} = 5.02$ TeV to constrain the shear and bulk viscosity to entropy density ratios, $η / s$ and $ζ / s$ . We demonstrate that the inclusion of spin polarization, which provides complementary sensitivity to the space-time structure and vorticity of the medium, shifts the posterior distribution of $ζ / s$ toward larger values, although current uncertainties do not allow a statistically significant separation at the 68% credibility level. Nevertheless, the results establish spin polarization as a valuable probe in quantitative studies of QGP transport properties and indicate that it should be incorporated in comprehensive and systematically constrained Bayesian extractions of the medium's dynamical parameters.
Comments:
35 pages, 16 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2605.29383 [pdf]
0 citations
02
[Submitted on 28 May 2026]
Narrowing the Gap Between Theory and Evaluations: Angular Momentum Distributions in Fission Fragments
Petar Marević🇭🇷 · Nicolas Schunck🇺🇸 · Marc Verriere🇫🇷
We present a microscopic framework for predicting angular momentum distributions over the full range of fission fragment masses and charges. For the neutron-induced fission of $^{235}$ U and $^{239}$ Pu, the obtained distributions exhibit a pronounced sawtooth pattern in average values, reveal a substantial isobaric dependence, and reproduce experimental photon multiplicities without adjustable parameters. These results demonstrate that microscopic theory is gradually becoming quantitatively competitive with phenomenological models.
Comments:
Submission to the proceedings from the 16th Nuclear Data for Science and Technology Conference held in Madrid, Spain, June 2025
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2605.29404 [pdf]
0 citations
03
[Submitted on 28 May 2026]
Large language model for unified and accurate description of multidimensional nuclear properties
S. J. Guo · S. Y. Wang · E. H. Wang · Z. M. Niu · Y. M. Ding
A prior-informed large language model (LLM) driven multi-task learning framework is proposed for the unified description of multiple nuclear observables. By fine-tuning the pre-trained DeepSeek-R1-1.5B model with Low-Rank Adaptation (LoRA), lightweight adapters are introduced while preserving general pre-trained parameters. Under a causal language modeling paradigm, the model is trained autoregressively on deviations between experimental and theoretical values. Significant accuracy improvements are achieved across seven observables, including charge radii, masses, binding energies, separation energies, and decay energies, with the training loss decreasing by over 98% across all tasks. This demonstrates that the LLM-based framework, through structured prior embedding, offers an efficient and shared approach for multi-task regression in fundamental nuclear properties.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2605.29408 [pdf]
0 citations
04
[Submitted on 28 May 2026]
Isospin-Based Supersymmetry in Neutron-Proton Pairing gap of fp-Shell Nuclei
Hossein Emami · Hadi Sabri
This study presents a systematic investigation of the effects of isospin, including both T=0 and T=/0 components, on nucleon pairing correlations in fp-shell nuclei. To this aim, the interacting boson model-4, which explicitly incorporates isospin and spin degrees of freedom, is employed to examine various mass formulas associated with neutron-proton correlations in atomic nuclei. Within this framework, neutron-proton pairing gaps are derived for the first time, providing a unified description of pairing correlations in even-even, odd-A, and odd-odd systems. Furthermore, to achieve a more realistic representation of local nuclear dynamics, effective asymmetric weighting coefficients are introduced into the conventional pairing-gap expressions, motivated by physical considerations related to shell structure, blocking effects, and isospin symmetry. These coefficients are determined through a fit to experimental binding-energy data and lead to a significant improvement in the agreement between theoretical predictions and observed systematic. Additionally, the results support the central assumption regarding the supersymmetry of the first fp-shell nuclei, highlighting the essential role of isospin-dependent effects in shaping neutron-proton pairing collectivity.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2605.29542 [pdf]
0 citations
05
[Submitted on 28 May 2026]
The polarization of thermal dileptons emitted in high-energy heavy-ion collisions
Han Gao🇨🇦 · Xiang-Yu Wu🇨🇦 · Charles Gale🇨🇦 · Greg Jackson🇫🇷 · Sangyong Jeon🇨🇦
This work presents calculations of thermal dilepton emission and polarization observables. It features a comprehensive framework which comprises virtual photon spectral functions complete at next-to-leading-order in the strong coupling and iEBE-MUSIC hydrodynamic simulations. The polarization of thermal lepton pairs is shown to be sensitive to in-medium properties of the quark-gluon plasma. We consider Pb+Pb collisions performed in conditions specific to the LHC and examine the magnitude and behaviour of the polarization as measured in different frames, the effects of the pre-equilibrium gluon abundance, and we derive a one-to-one mapping between dielectron and dimuon polarization.
Comments:
17 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2605.30180 [pdf]
2 citations
06
[Submitted on 28 May 2026]
Qubit-efficient variational algorithm for nuclear structure
Chandan Sarma🇬🇧 · Paul Stevenson🇬🇧
In this work, we compare three qubit-mapping strategies to study the structure of the nuclear ground state within the shell model description employing the Variational Quantum Eigensolver (VQE) approach. Although the initial point for different mappings is a Hamiltonian matrix in many-body particle basis or Slater determinant (SD) basis, the structure of the trial wavefunction and resource counts are different for each mapping. These three mappings are tested for a mid $p$ -shell nucleus $^{10}$ B and compared the quantum resources required to find the ground state for each mapping. Further, we extend the qubit-efficient mapping to study the ground state of one more mid $p$ -shell nucleus $^{12}$ C. We run circuits up to 26-qubits representing their ground states on a noisy simulator (IBM's FakeFez backend) and quantum hardware ( $ibm_f ez$ ). The best post-error mitigated results from the hardware for $^{10}$ B ground state is obtained following SD to qubit mapping with a percent error of 0.21 \%. The percent errors for the same state following cSD and pnSD mapping are 3.37 and 8.88 \%, respectively. On the other hand, following the cSD mapping, the post-error mitigated ground state energy of $^{12}$ C is 6.82 \% away from the exact result. We further evaluate the fidelity of the VQE wavefunctions obtained from hardware with respect to the shell model wavefunctions for the cSD mapping. This cSD mapping can be useful for scaling the VQE algorithm for complex nuclei across different mass regions in terms of qubit efficiency.
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2605.30261 [pdf]
0 citations
07
[Submitted on 27 May 2026] (cross-list from hep-lat)
First steps towards gauge-independent vortex identification through machine learning
Wyatt A. Smith🇺🇸 · César Fernández-Ramírez🇪🇸 · Jeff Greensite🇺🇸 · Adam P. Szczepaniak🇺🇸
As a first step towards machine identification of confining objects in thermalized lattice gauge configurations, we present our 2dVoId model for center vortex identification on pure SU(2) lattices in $D = 2$ dimensions. We create a training set by inserting thin Z2 vortices at various locations on a zero action lattice, and then distort those configurations by applying random SU(2) gauge transformations, noise, and by thickening the vortices via cooling. For moderate vortex visibility, our model is able to reliably identify the location of center vortices. We additionally demonstrate scalability through tiling strategies, which will enable generalization to higher dimensions while reducing training costs.
Comments:
10 pages, 8 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2605.29109 [pdf]
0 citations
08
[Submitted on 28 May 2026] (cross-list from hep-lat)
Higher Mellin Moments of the Unpolarized PDF of the Pion and the Kaon from Lattice QCD
Constantia Alexandrou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · Simone Bacchio (The Cyprus Inst.)🇨🇾 · Priyajit Jana (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · Marcus Petschlies (Univ. of Bonn)🇩🇪 · Luis Alberto Rodriguez Chacon (The Cyprus Inst. and Univ. of Ferrara)🇨🇾 · Gregoris Spanoudes (Univ. of Cyprus)🇨🇾 · Fernanda Steffens (Univ. of Bonn)🇩🇪 · Carsten Urbach (Univ. of Bonn)🇩🇪 · Urs Wenger (Univ. of Bern)🇨🇭
We present results on the Mellin moments of the unpolarized parton distribution function (PDF) of the pion and kaon up to the fourth order. The computation is done using one $N_{f} = 2 + 1 + 1$ gauge ensemble of twisted mass fermions with quark masses tuned to approximately their physical values. We reconstruct the valence pion and kaon PDFs using the connected contributions to the three Mellin moments. We compare our results on the Mellin moments and the reconstructed PDFs with other lattice QCD and phenomenological determinations.
Comments:
14 pages and 14 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2605.29998 [pdf]
3 citations
09
[Submitted on 28 May 2026] (cross-list from hep-lat)
Mellin Moments of the Unpolarized Gluon PDF in the Proton from Nonlocal Operators in Lattice QCD
Joseph Delmar🇺🇸 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Yong Zhao🇺🇸
We present a lattice QCD determination of the Mellin moments of the unpolarized gluon parton distribution function in the proton. The analysis is based on matrix elements of nonlocal gluon operators coupled to momentum-boosted proton states. The calculation relies on an $N_{f} = 2 + 1 + 1$ ensemble of maximally twisted mass fermions with clover improvement and the Iwasaki-improved gauge action, at a pion mass of approximately 260 MeV. Working within the short-distance operator product expansion (OPE) of the reduced gluon Ioffe-time distribution, we extract ratios of higher-order gluon moments, $⟨ x^{n} ⟩$ with $n > 1$ , to the gluon momentum fraction, $⟨ x ⟩$ . We investigate systematic effects associated with the truncation of the order of moment in the OPE, the choice of minimum and maximum Wilson-line separations entering the analysis, and the treatment of mixing with the quark-singlet under perturbative matching. The stability of the extracted moments is further studied under scale evolution using DGLAP equations, allowing us to assess uncertainties related to perturbative truncation by varying the scale. Our work provides a determination of the ratio $⟨ x^{3} ⟩_{g} / ⟨ x ⟩_{g}$ at a scale of 2 GeV, with uncertainties that account for both statistical and the dominant theoretical systematic uncertainties.
Comments:
17 pages, 7 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2605.30193 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE