Nuclear Theory·nucl-th

Tuesday·June 2, 2026

19 papers—10 primary·9 cross-listed

11
[Submitted on 29 May 2026] (cross-list from nucl-ex)
Dependence of two-particle azimuthal correlations on the forward rapidity gap width in pPb collisions at $s_{NN}$ = 8.16 TeV
CMS Collaboration
One of the most striking features of relativistic heavy ion collisions is the presence of collective flow of thousands of produced particles. This flow can be characterized by the Fourier coefficients ( $V_{n Δ}$ ) of the azimuthal angular distributions of charged particles, and its existence can be explained by the formation of a quark gluon plasma, which behaves as a fluid. Surprisingly, the angular distributions of particles from very small systems such as proton-lead (pPb), proton-proton (pp), electron-positron, and photon-proton ( $γ$ p) collisions also exhibit non-zero Fourier coefficients, raising the question of whether collective flow is present. This paper presents measurements of $V_{n Δ}$ from a sample of pPb events at $s_{NN}$ = 8.16 TeV that are enriched in photon-lead ( $γ$ Pb) and pomeron-lead ( $I P$ Pb) interactions by requiring no particles in the proton-going region. Measurements are made as a function of the forward rapidity gap width (the rapidity range in which no particles are found), the transverse momentum of the particles, and the multiplicity of particles in the event. The results are compared to previous measurements of pp, pPb, and $γ$ p+ $I P$ p events as well as modern event generators.
Comments:
Submitted to Physical Review C. All figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-22-004 (CMS Public Pages)
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2606.00171 [pdf]
0 citations
12
[Submitted on 30 May 2026] (cross-list from nucl-ex)
Investigation of the onset of deconfinement with the NA61/SHINE experiment
A. Bazgir🇵🇱
High-energy heavy-ion collisions provide a unique framework for studying the phase transition of strongly interacting matter. The NA61/SHINE experiment, located in the North Area of CERN's SPS, is a fixed-target facility designed to perform a systematic exploration of the QCD phase diagram. This is achieved through a two-dimensional scan that varies both the beam momentum (from 13A to 150/158A GeV/c) and the size of the colliding systems (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb, O+O). Such a wide scan enables detailed studies of how collision dynamics evolve with system size and energy. A central objective of the NA61/SHINE research program is to investigate the onset of deconfinement - the transition from hadronic matter to a quark-gluon plasma (QGP) - by analyzing observables such as the strangeness-to-entropy ratio, where entropy is proportional to pion yields. According to the Statistical Model of the Early Stage (SMES), this ratio is expected to exhibit a horn-like structure within the SPS energy range. This article discusses the theoretical framework of the SMES, its assumptions, and compares recent NA61/SHINE results with other experimental data worldwide, contributing to a deeper understanding of the QCD phase transition.
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2606.00597 [pdf]
0 citations
13
[Submitted on 30 May 2026] (cross-list from physics.data-an)
Proton High-Order Cumulants in Au+Au Collisions at High Baryon Density from JAM with a Centrality-Independent Framework
Yongcong Xu🇨🇳 · Zhaohui Wang🇨🇳 · Yu Zhang🇨🇳 · Xiaofeng Luo🇨🇳
The event-by-event higher-order cumulants of conserved quantities such as net-baryon, net-electric charge, and net-strangeness in heavy-ion collisions have been extensively utilized in experimental searches for the QCD critical point, notably in the RHIC-STAR experiment. In this study, we conduct a systematic analysis of higher-order cumulants of proton number distributions in Au+Au collisions at center-of-mass energies of $s_{NN} = 3.2$ , $3.5$ , $3.9$ , and $4.5$ GeV using the JAM model. We calculate cumulants, factorial cumulants, and their ratios using a novel method, Centrality-Independent Genuine Cumulant Analysis fRamework (CIGAR), which effectively eliminates initial volume fluctuations. We comprehensively compare the CIGAR method with the traditional Centrality Bin Width Correction (CBWC) method. In addition, the effect of spectators on cumulant is systematically investigated. Our results provide a dynamic non-critical baseline in the high-baryon-density regime which is crucial for QCD critical point searches in heavy-ion collisions.
Comments:
10 pages, 8 figures
Subjects:
Data Analysis, Statistics and Probability (physics.data-an); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2606.00786 [pdf]
0 citations
14
[Submitted on 30 May 2026] (cross-list from cond-mat.quant-gas)
Three- and four-boson systems expanded around the unitarity limit: Application to $^{4}$ He
Feng Wu🇫🇷 · Xincheng Lin🇺🇸 · Ubirajara van Kolck🇫🇷 · Sebastian König🇺🇸
The three- and four-boson systems with a large scattering length and a short effective range in the two-body sector are studied in the framework of Short-Range Effective Field Theory. The starting point (leading order) of the EFT is taken to be the universal unitarity limit, where the two-body sector is parameter-free and only one three-body parameter enters. In this limit, physical systems manifests discrete scale invariance. Deviations from universality arising from finite scattering-length and effective-range corrections, as well as a four-body force required by renormalization, are included perturbatively at next-to-leading order. The three-body ground state and its associated four-body ground and first-excited states are studied using the Faddeev-Yakubovsky formalism and a complementary diagrammatic approach. By employing techniques to remove contributions from deep trimers in tetramer calculations, we extend our analysis to larger cutoffs than previously accessible within the FY approach. Our results for binding energies and radii of $^{4}$ He three- and four-atom systems converge well to results obtained with sophisticated phenomenological potentials. These successes suggest that the physics of $^{4}$ He atomic clusters is governed by only small deviations from discrete scale invariance.
Comments:
29 pages, 20 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2606.00854 [pdf]
1 citation
15
[Submitted on 31 May 2026] (cross-list from hep-th)
Pseudo-Gauge Stabilizers and Fibration Structure of the Cooper--Frye Map at Freeze-Out
Jiahua Tian🇨🇳
We study the pseudo-gauge transformation (PGT) freedom at freeze-out in relativistic spin hydrodynamics. The Cooper--Frye map is shown to factor through the quotient of freeze-out data by a universal stabilizer, yielding a stratified fibration over the space of thermodynamic Lagrange multipliers. This classifies observables into base and fiber types, bounds the number of independent PGT-sensitive observables by the family-restricted fiber dimension, and implies cross-observable consistency relations. Applied to heavy-ion polarization data, the fibration structure provides a structural interpretation of the tension between $Λ$ polarization and $ϕ$ -meson spin alignment as evidence that the vorticity-dominated response sector may need to be enlarged with local field-correlation data. We show that Weyl-anomaly-induced currents studied recently are classified as base observables and recover the known Belinfante--canonical obstruction $Ω_{ab} \neq = ϖ_{ab}$ from the stabilizer condition.
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2606.01429 [pdf]
0 citations
16
[Submitted on 1 Jun 2026] (cross-list from hep-ph)
Azimuthal decorrelation in diffractive dijet production
Ding Yu Shao🇨🇳 · Yu Shi🇨🇳 · Cheng Zhang🇨🇳 · Jian Zhou🇨🇳 · Ya-jin Zhou🇨🇳
We calculate the azimuthal angular decorrelation of diffractive dijets in ultra-peripheral heavy-ion, $e p$ , and $e A$ collisions to probe non-perturbative diffractive transverse momentum-dependent distributions. Focusing on the dominant semi-inclusive channel with an unobserved semi-hard gluon, we perform an all-order resummation of soft gluon emissions for the transverse energy-energy correlator observable, accounting for both initial and final state radiation. We also analyze heavy-quark pair production and demonstrate the sensitivity of the decorrelation to the jet axis definition. Finally, we provide numerical predictions for relevant kinematics at LHC UPCs, HERA, and the future EIC. Our results demonstrate that the acoplanarity of diffractive dijet production could serve as a promising probe of diffractive transverse momentum-dependent distributions.
Comments:
29 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2606.02230 [pdf]
1 citation
17
[Submitted on 1 Jun 2026] (cross-list from nucl-ex)
Studies of $^{144, 148} Sm + α$ potential for the $p$ -process nucleosynthesis
C. Soto🇫🇷 · C. Ducoin🇫🇷 · N. Millard-Pinard🇫🇷 · B. M. Rebeiro🇫🇷 · O. Stézowski🇫🇷 · N. de Séréville🇫🇷 · F. Hammache🇫🇷 · A. Chalil🇫🇷 · Y. Demane🇫🇷 · C. Bachelet🇫🇷 · J.-C. Thomas🇫🇷 · M. Assié🇫🇷 and 12 other authors
Nucleosynthesis reaction networks leading to $p$ -nuclei involve a combination of different types of photodisintegration and capture reactions, as well as $β^{+}$ decays or electron captures. Photodisintegration reactions involving $α$ particles present a particular interest as they serve as branching points of the reaction networks. The cross sections of these reactions depend crucially on the $α$ -nucleus interaction. The $α$ optical model potential (AOMP) is determined mostly by means of experimental differential elastic scattering distributions. Several previous studies have focused on the case of $^{144} Sm$ , an intriguing $p$ -nucleus that is semi-magic with 82 neutrons. This work presents new experimental data on $α$ elastic and inelastic scattering on $^{148} Sm$ , its closest stable isotope. Isotopic effects on the description of the AOMP are studied, as well as their consequences on the prediction of $α$ -induced reaction cross sections at astrophysical energies. It is shown that the isotopic ratio for $(α, γ)$ cross sections can be multiplied up to a factor of two when these effects are included.
Comments:
Submitted to Phys. Rev. C
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2606.02266 [pdf]
0 citations
18
[Submitted on 1 Jun 2026] (cross-list from hep-ph)
Probing Pair Correlations in QCD Matter with Photon Spectra
Xingjian Lu🇨🇳 · Shuzhe Shi🇨🇳
Correlations in the phase-space distribution of partons play an important role in the initial stage of relativistic heavy-ion collisions, where the matter is dense and far from equilibrium. Photons produced in the hot medium, which predominantly originate from two-parton initial states, are sensitive to two-particle correlations in the phase-space distribution. In this work, we study how pair correlations in non-equilibrium QCD matter affect in-medium photon production. We decompose the two-particle distribution as $F_{ab} = f_{a} f_{b} + g_{ab}$ , where $g_{ab}$ is the pair correlation. Focusing on the $2 \to 2$ quark--antiquark annihilation and Compton channels, we compute the leading-logarithmic photon spectrum by expanding the single-particle distribution and pair correlation in a spectral basis, thereby accommodating a broad class of two-particle distributions. For a rotationally invariant medium, we find that relative-angle modes of the pair correlation generate sign-changing modifications to the photon spectrum, with magnitudes that can be comparable to the factorized contribution. Thus, photon spectra, although single-particle observables, can measure the momentum correlations of the emitting medium and therefore probe the early-time hydrodynamization.
Comments:
12 pages, 6 figures,
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2606.02414 [pdf]
0 citations
19
[Submitted on 1 Jun 2026] (cross-list from hep-th)
Cumulant dynamics in finite-memory diffusion
Navid Abbasi🇨🇳 · Xin An🇧🇪 · Shanjin Wu🇨🇳
Fluctuations of conserved charges are among the main proposed signatures of the quantum chromodynamics (QCD) critical point, but their interpretation requires a dynamical description of how fluctuation correlators evolve during the finite lifetime of the quark--gluon plasma (QGP) fireball. The standard baseline for this evolution is Fickian diffusion, in which the diffusive current follows the local density gradient instantaneously. This instantaneous-current limit can miss delayed-response effects when the current-relaxation time becomes comparable to the relaxation time of the relevant fluctuation modes. In this work we extend this baseline to Maxwell--Cattaneo diffusion, where the current relaxes on a finite time scale and therefore retains memory. We derive closed evolution equations for multi-point Wigner functions and convert the freezeout correlators into acceptance-dependent cumulants along representative trajectories in the QCD phase diagram. While Fickian diffusion already causes the correlators to lag behind their instantaneous equilibrium values, finite current relaxation introduces an additional memory effect beyond this diffusive lag. As a result, current memory can suppress, shift, and reshape the non-monotonic behavior of the cumulants relative to both instantaneous equilibrium and Fickian diffusion, with the most visible effects appearing in higher-order cumulants and their ratios.
Comments:
49 pages, 10 figures
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2606.02446 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE