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Nuclear Theory·nucl-th

Thursday·September 3, 2026

6 papers—5 primary·1 cross-listed

All6Primary5Cross-lists1
  1. 01

    [Submitted on 1 Sept 2026]

    Unveiling QCD Criticality with Cross-Rapidity Net-Baryon Cumulants

    Jianing Li · Shuzhe Shi · Lipei Du

    Fluctuations of conserved charges are a primary tool in the search for the QCD critical endpoint, but their beam-energy dependence is complicated by global baryon-number conservation, whose influence changes as the experimental acceptance covers different fractions of the collision system. We propose using correlations of net-baryon fluctuations between two separated rapidity windows to exploit the distinct signatures of conservation and critical dynamics. Global conservation produces a negative cross-window correlation, whereas a common long-wavelength critical fluctuation produces a positive one. We show that, within a canonical independent-source framework, the conservation-induced background and the critical signal enter additively at leading order, allowing the leading conservation term to be estimated and subtracted. The resulting yield-scaled correlator follows the nonmonotonic enhancement of an Ising-mapped equilibrium correlation length along a freeze-out trajectory passing near a hypothetical critical endpoint, while wider rapidity windows reduce the response through thermal smearing. Cross-rapidity cumulants therefore provide a rapidity-differential strategy for reducing the leading conservation background and sharpening fluctuation-based searches for QCD criticality in beam-energy-scan experiments.

    Comments:
    15 pages, 4 figures. Comments and suggestions are welcome
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2609.01859 [pdf]
    0 citations
  2. 02

    [Submitted on 2 Sept 2026]

    Spin transport in intermediate-energy heavy-ion collisions

    Jun Xu · Bao-An Li

    In this mini-review, we provide a brief status report on investigating spin transport phenomena in intermediate-energy heavy-ion collisions by simulating solutions of the spin- and isospin-dependent Boltzmann-Uehling-Uhlenbeck (SIBUU) transport equation using the test-particle method. We outline the physics foundation and technical approach, summarize our main results and identify key challenges in further studying spin transport within the SIBUU framework. As examples, we show how the global and local spin polarizations of nucleons, the spin splitting of nucleon collective flows as well as flows of light clusters at different spin states can be used to explore interesting new physics associated with the nuclear spin-orbit potential in dense neutron-rich medium. The spin-orbit potential and the rigorous angular momentum conservation are also shown to affect spin-averaged observables. Hopefully the new findings and challenges identified here will stimulate further studies both theoretically and experimentally on spin transport in intermediate-energy heavy-ion collisions.

    Comments:
    21 pages, 15 figures, invited mini-review
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex)
    arXiv:
    2609.01994 [pdf]
  3. 03

    [Submitted on 2 Sept 2026]

    Impact of nuclear triaxial deformation on electromagnetic fields in relativistic collisions

    Maidi Huang · Jin Hu · Yunpeng Liu · Baoyi Chen

    Electromagnetic fields produced in relativistic heavy-ion collisions depend sensitively on the initial spatial distribution of nuclear charge. Using the Liénard--Wiechert potential with a triaxially deformed Woods--Saxon density, we calculate the transverse electric and magnetic field distributions in collisions at . We systematically examine how the triaxiality angle modifies the field structure at the collision time () in semi-central events, using spherical nuclear collisions as a baseline. The results show that nuclear triaxiality causes distinct spatial redistributions of both electric and magnetic fields in the transverse plane. These findings indicate that initial electromagnetic fields encode key information on intrinsic nuclear shapes, offering an additional constraint on nuclear deformation and its consequences for field-sensitive observables in heavy-ion collisions.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2609.02053 [pdf]
    0 citations
  4. 04

    [Submitted on 2 Sept 2026]

    Effects of Strong Magnetic Fields on the Equation of State and Mass-Radius Structure of Hyperonic Neutron-Star Matter with Anomalous Magnetic Moments

    W. German · T. Mello · J. P. W. Diener · G. C. Hillhouse

    We investigate the effects of strong magnetic fields on the equation of state (EoS) and stellar structure of cold, charge-neutral, -equilibrated hyperonic neutron-star matter within a relativistic mean-field (RMF) framework. The matter sector contains the full baryon octet and leptons, while charged particles are Landau quantized and all baryons are coupled to the magnetic field through their anomalous magnetic moments (AMM). The calculation is performed with the RMF FSU2H hyperonic parameterization and compared for zero field, constant magnetic fields, and density-dependent magnetic-field profiles. We find that strong magnetic fields modify the hyperonic composition through the competing effects of Landau quantization and AMM-induced spin splitting. Landau quantization softens the magnetized hyperonic equation of state. The inclusion of AMM provides an additional magnetic stiffening mechanism in hyperonic matter. The results for the inclusion of the AMM coupling and not are still consistent with observations of - neutron stars and small radii. The present work therefore provides a benchmark for assessing the influence of AMM on the composition, magnetization, equation of state, and mass-radius structure of magnetized hyperonic neutron-star matter.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2609.02441 [pdf]
    0 citations
  5. 05

    [Submitted on 2 Sept 2026]

    Clustered Nature of Hot and Dense Nuclear Matter: A quantum statistical approach

    G. Röpke · H. Pais · J. B. Natowitz · D. Blaschke

    The equilibrium abundances of the light clusters H, H, He, He in hot nuclear matter at densities near the saturation density are of essential interest for nuclear physics and astrophysical applications, but theoretical approaches give diverging answers. We compare the quantum statistical approach with the recently discussed phase-space excluded-volume approach. We analyze the main ingredients, the Mott momentum, and the momentum distribution functions of light clusters. We observe a sharp decrease in cluster abundances as the density approaches saturation density, that is also seen in a relativistic mean-field calculation. We outline possible improvements in determining the composition of hot, dense matter in thermodynamic equilibrium. Non-equilibrium effects must be taken into account to investigate cluster formation in heavy-ion collisions.

    Comments:
    9 pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2609.02463 [pdf]
    0 citations