Nuclear Theory·nucl-th

Wednesday·March 4, 2026

9 papers—4 primary·5 cross-listed

01
Spin hydrodynamics on a hyperbolic expanding background
Rajeev Singh🇷🇴 · Alexander Soloviev🇸🇮
We study relativistic spin hydrodynamics on the hyperbolic $κ = - 1$ flow background recently identified by Grozdanov. This background corresponds to an $S O (2, 1)$ -invariant, transversely expanding solution with finite spacetime support in Minkowski space, in contrast to the well-known Gubser flow $(κ = + 1)$ which possesses $S O (3)$ symmetry and infinite transverse extent. Working within the formulation of perfect-fluid spin hydrodynamics, we derive the exact evolution equations for all spin components of the spin potential on the $κ = - 1$ background. We find that the enhanced early-time expansion rate and the presence of a causal edge lead to a stronger localization of spin dynamics compared to the Gubser case. Remarkably, the azimuthal component of the spin potential oscillates as it decays in the forward lightcone, in stark contrast to the Gubser flow. Thus, our results establish the $κ = - 1$ flow as a distinct and physically meaningful benchmark for studying spin dynamics in expanding relativistic fluids with finite spacetime support.
nucl-thhep-phhep-th4 citations
02
Unshadowing the constituent quark number scaling of harmonic flow in heavy-ion collisions
Tom Reichert🇨🇭 · Iurii Karpenko🇨🇿
Constituent quark number scaling of elliptic flow has been proposed as one key observable to identify the phase transition or the absence of the Quark-Gluon Plasma (QGP) in heavy-ion collisions. At the fixed target program at RHIC the STAR collaboration has recently reported that NCQ scaling breaks when decreasing the collision energy from $s_{NN} = 4.5$ to $3.0$ GeV. However, the generation of elliptic flow is dominated by a highly intricate interplay of spectator shadowing, squeeze-out and geometry dependent hadron emission governed by their cross sections. Therefore in this article we will disentangle the shadowing contribution from the harmonic flow signal of the particle emitting source, effectively ``unshadowing'' the source. We introduce Fourier coefficients that quantify the azimuthal absorption rate of hadrons decoupling from the system. We benchmark the derived results using a toy model based on a ballistic Glauber description of the penetrating nuclei and calculate how shadowing qualitatively alters the constituent quark number scaling of the hadron emitting source. The results are thus relevant for interpreting recent STAR measurements as well as the upcoming measurements by CBM at FAIR.
nucl-thnucl-ex0 citations
03
Effects of isovector spin-orbit interaction on the charge-weak form factor difference in $^{48}$ Ca, $^{208}$ Pb, $^{90}$ Zr and $^{62}$ Ni
Tong-Gang Yue🇨🇳 · Zhen Zhang🇨🇳 · Lie-Wen Chen🇨🇳
The nucleon spin-orbit interaction is a cornerstone of nuclear structure theory, yet its isospin dependence remains insufficiently constrained within modern nuclear energy density functional (EDF) theory. It was recently shown that, within the framework of extended Skyrme EDFs, the charge-weak form factor difference $Δ F_{CW}$ in $^{48}$ Ca exhibits remarkable sensitivity to the effective isovector spin-orbit (IVSO) interaction, whereas $Δ F_{CW}$ in $^{208}$ Pb is much less sensitive to this channel. Extending this analysis to other nuclei, we find that $^{90}$ Zr, with its ten spin-orbit unpaired $1 g_{9/2}$ neutrons, displays a $Δ F_{CW}$ sensitivity to the IVSO strength similar to that of $^{48}$ Ca, arising from modifications to the central mean-field potential rather than the one-body spin-orbit potential. In contrast, $^{62}$ Ni, like $^{208}$ Pb, remains largely insensitive to the IVSO interaction. This structure-driven distinction suggests an experimental strategy: future parity-violating electron scattering measurements, e.g., the MREX experiment at the MESA facility, on $^{48}$ Ca and $^{90}$ Zr would help constrain the effective IVSO strength, while measurements on $^{208}$ Pb and $^{62}$ Ni can provide a cleaner probe of the density dependence of the symmetry energy with reduced IVSO sensitivity.
nucl-thastro-ph.HEhep-phnucl-exParticles(2026)·0 citations
04
Relativistic distorted-wave analysis of the missing-energy spectrum measured with monochromatic $ν_{μ}$ - $^{12}$ C interactions at JSNS $^{2}$
J. M. Franco-Patino · J. García-Marcos · V. Belocchi · M. B. Barbaro · G. Co' · R. González-Jiménez
Recently, the JSNS $^{2}$ collaboration measured for the first time the missing-energy distribution of $^{12}$ C using a monochromatic neutrino beam coming from kaon decays at rest. In this work we present the results of an analysis of this spectrum using the relativistic distorted-wave approach. A new parameterization of the spectral function for neutrons in $^{12}$ C, which incorporates detailed information from $(e, e^{'} p)$ experiments with high missing-energy resolution has been used. The role of the recoil of the residual nucleus, final-state interactions, and neutrino event generators are discussed.
nucl-thnucl-exPRD(2026)·2 citations
05
One-point energy correlator for deep inelastic scattering at small $x$
Zhong-Bo Kang🇺🇸 · Robert Kao🇺🇸 · Meijian Li🇪🇸 · Jani Penttala🇺🇸
We derive the expressions for the one-point energy correlator (OPEC) in deep inelastic scattering in the high-energy (small- $x$ ) limit within the Color Glass Condensate framework. The OPEC is computed as a function of the angle between the energy flow and the target proton or nucleus, enabling a systematic exploration of different momentum scales in the scattering process. Owing to the momentum sum rule, the dependence on fragmentation functions cancels, leaving the dipole amplitude as the only nonperturbative input. As a result, the OPEC provides a clean and direct probe of gluon saturation dynamics at small $x$ . We present numerical results for representative kinematic configurations relevant to the future Electron--Ion Collider, demonstrating sizable nuclear suppression effects and highlighting the sensitivity of this observable to saturation phenomena.
↳ hep-phhep-exnucl-exnucl-th5 citations
06
Weinberg Angle, Neutron Abundance in BBN, and Lifetime
Cheng Tao Yang🇺🇸 · Johann Rafelski🇺🇸
We present state of the art kinetic theory determination of the neutron abundance available for the Big-Bang nucleosynthesis (BBN). Our work is motivated by the study of the neutron lifespan measured in the laboratory and the unknown strength of weak interactions coupling constant $G_{F}$ at finite temperature in the primordial Universe. We draw attention to the relevant dependence of $G_{F}$ on the symmetry breaking Weinberg angle $s_{W}^{2}$ , a free parameter in the standard model of particle physics. We establish how the value of $s_{W}^{2}$ by way of $G_{F}$ modification influences neutron abundance available for BBN and neutron lifetime.
↳ hep-phastro-ph.COnucl-thParticles(2026)·0 citations
07
Emergent Gribov horizon kernel from replica symmetry breaking in Yang--Mills theories
Rodrigo Carmo Terin🇪🇸
We show that, in the replica-broken sector of the Serreau--Tissier (ST) gauge fixing, the expansion of the replica determinant in the regulator $ζ$ induces a nonlocal bilinear gluonic kernel with the same color and Lorentz structure as the quadratic part of the BRST-invariant Gribov horizon functional. This establishes an effective leading-order correspondence with the refined Gribov-Zwanziger (RGZ) horizon sector, rather than a reconstruction of the full nonlinear functional $H (A^{h})$ . The induced scale satisfies $γ_{ind}^{4} \propto ζ$ at leading order, up to scheme-dependent normalization and higher-order corrections. Depending on the replica phase, the ST sector yields either a local Curci--Ferrari (CF) screening mass or an induced RGZ-type horizon kernel, avoiding double counting of infrared scales.
↳ hep-thhep-lathep-phnucl-thEPJC(2026)·2 citations
08
Scattering and Femtoscopic Correlation Functions of the $Σ_{c}^{++} π^{+}$ , $Σ_{c}^{0} π^{-}$ and $Σ_{b}^{+} π^{+}$ Systems
Mikel F. Barbat🇪🇸 · Juan Nieves🇪🇸 · Laura Tolos🇪🇸
We present predictions for scattering observables and femtoscopic correlation functions (CFs) of the $I = 2$ $Σ_{c}^{++} π^{+}$ , $Σ_{c}^{0} π^{-}$ systems and its heavy-flavor counterpart $Σ_{b}^{+} π^{+}$ . In both heavy-quark sectors, the strong interaction is formulated within two distinct theoretical frameworks, each constrained to reproduce the lowest-lying odd-parity isoscalar spin- $1/2$ resonances, $Λ_{c} (2595)$ and $Λ_{b} (5912)$ , respectively. While the $Σ_{c}^{0} π^{-}$ pair is governed solely by the strong interaction, electrostatic contributions are included in the other two channels involving charged particles through relativistic Coulomb wave functions. We show that the differences observed in the scattering observables between the two strong-interaction models arise mainly from the specific ultraviolet regularization schemes employed. The inclusion of Coulomb effects induces only a very small increase in both the scattering length and the effective range. The resulting CFs in the charm and bottom sectors display analogous global features, in agreement with expectations from heavy-quark flavor symmetry. Both, the $Σ_{c}^{++} π^{+}$ and $Σ_{b}^{+} π^{+}$ CFs, when computed including only the strong interaction, exhibits substantial discriminating power among the different models. However, once Coulomb effects are incorporated, the CFs become largely affected by the repulsive electrostatic interaction, which diminishes their sensitivity to the details of the underlying strong dynamics, thereby reducing the capability to differentiate between theoretical descriptions. Thus, the $Σ_{c}^{0} π^{-}$ CF-being free from Coulomb effects-provides the most suitable observable for constraining the strong dynamics of the isotensor $Σ_{c} π$ system.
↳ hep-phnucl-thPLB(2026)·1 citation
09
Momentum-projected hadron entanglement from lattice-QCD replica correlators
Kiminad A. Mamo🇺🇸
We define a finite-volume lattice-QCD density-matrix observable for the vacuum-subtracted spatial R'enyi response of a source-sink-prepared, momentum-projected hadron. At fixed regulator, integer R'enyi index $n > 1$ , spatial region $B_{R}$ , spin projection, gauge-theory cut prescription $C$ , and after the usual double-sided source-sink projection, the central result is an exact source-sink replica identity: the response is obtained from the logarithm of a replicated hadron correlator on the cut geometry normalized by the corresponding power of the ordinary one-sheet correlator. This identity makes the natural first numerical target the two-sheet $n = 2$ measurement of the replicated source-sink correlator ratio, together with a finite-volume test of whether the response scales as $L^{- 3}$ at fixed physical $R$ . The exponent is a lattice output to be tested, not an input theorem for the nonlinear R'enyi functional. The construction is prescription-defined in gauge theory, and full QCD requires the replicated sea-quark determinant and valence contractions on the replicated cut graph; quenched and partially quenched calculations are therefore pilots. Large- $N_{c}$ two-dimensional QCD provides an interacting benchmark in which the matched one-meson response is suppressed by the inverse spatial volume, with the short-interval coefficient controlled by light-front PDF moments.
↳ hep-phhep-lathep-thnucl-th2 citations

Affiliations

first authorsco-authorsvia INSPIRE