Nuclear Theory·nucl-th

Thursday·March 27, 2025

12 papers—4 primary·8 cross-listed

01
Viscous Gubser flow with conserved charges to benchmark fluid simulations
Kevin Ingles🇺🇸 · Jordi Salinas San Martín🇺🇸 · Willian Serenone🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
We present semi-analytical solutions for the evolution of both the temperature and chemical potentials for viscous Gubser flow with conserved charges. Such a solution can be especially useful in testing numerical codes intended to simulate relativistic fluids with large chemical potentials. The freeze-out hypersurface profiles for constant energy density are calculated, along with the corresponding normal vectors and presented as a new unit test for numerical codes. We also compare the influence of the equation of state on the semi-analytical solutions. We benchmark the newly developed Smoothed Particle Hydrodynamics (SPH) code CCAKE that includes both shear viscosity and three conserved charges. The numerical solutions are in excellent agreement with the semi-analytical solution and also are able to accurately reproduce the hypersurface at freeze-out.
nucl-thhep-thphysics.flu-dynPRC(2026)·3 citations
02
Magnetodynamic Characteristics and QGP Energy Dissipation in RMHD Framework with Relativistic Heavy-Ion Collisions
Huang-Jing Zheng🇨🇳 · Sheng-Qin Feng🇨🇳
Relativistic heavy-ion collisions generate ultra-strong magnetic fields that interact with the quark-gluon plasma (QGP), a key focus of high-energy physics research.This study investigates QGP energy density evolution under time-dependent magnetic fields within a (1 +1)D relativistic magnetohydrodynamic (RMHD) framework integrated with Bjorken flow. Three magnetic field temporal evolution models (Type-1,Type-2,Type-3) are analyzed for two different equations of state: (1) $p = c_{s}^{2} e$ , and (2) $p = c_{s}^{2} e - 2 M B$ incorporating a temperature-dependent magnetic susceptibility derived from lattice QCD. Results show that stronger magnetic fields consistently suppress QGP energy density decay,with suppression magnitude dependent on the magnetic field's temporal profile. Ultra-relativistic fluids exhibit slowed energy decay due to magnetic pressure counteracting hydrodynamic expansion.In contrast,magnetized conformal fluids display faster energy dissipation under identical conditions, arising from the synergistic effect of enhanced magnetic fluid coupling,increased energy dissipation during interaction,and QGP's perfect fluid expansion at elevated temperatures.Temperature-dependent magnetic susceptibility reveals a transition from diamagnetic (confined phase) to paramagnetic (deconfined QGP phase) behavior, introducing a feedback mechanism that strengthens energy retention at higher temperatures. This work clarifies the interplay between magnetic field dynamics,QCD phase structure, and hydrodynamic expansion, providing key observational signatures for distinguishing fluid types in heavy-ion collisions and advancing realistic modeling of magnetized QGP.
nucl-thhep-phParticles(2026)·2 citations
03
Effects of quark core sizes of baryons in neutron star matter
Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸
We describe the quark substructure of hadrons and the equation of state of high density neutron star matter by using the Nambu $-$ Jona-Lasinio (NJL) model, which is an effective quark theory based on QCD. The interaction between quarks fully respects the chiral and flavor symmetries. Guided by the success of various low energy theorems, we assume that the explicit breaking of these symmetries occurs only via the current quark masses, and all other symmetry breakings are of dynamical nature. In order to take into account the effects of the finite quark core sizes of the baryons on the equation of state, we make use of an excluded volume framework which respects thermodynamic consistency. The effects generated by the swelling quark cores generally act repulsively and lead to an increase of the pressure with increasing baryon density. On the other hand, in neutron star matter they also lead to a decrease of the density window where hyperons appear, because it becomes energetically more favorable to convert the faster moving nucleons into hyperons. Our quantitative analysis shows that the net effect of the excluded volume is too small to solve the long standing "hyperon puzzle," which is posed by the large observed masses of neutron stars. Thus the puzzle persists in a relativistic effective quark theory which takes into account the short range repulsion between baryons caused by their finite and swelling quark core sizes in a phenomenological way.
nucl-thhep-phSymmetry(2025)·6 citations
04
High-Precision Ab Initio Radius Calculations of Boron Isotopes
Tobias Wolfgruber · Tobias Gesser · Marco Knöll · Pieter Maris · Robert Roth
We perform a precision study of radii in Boron isotopes for multiple realistic interactions from chiral effective field theory. We obtain predictions of radii with combined many-body and interaction uncertainty quantification from ab initio no-core shell model calculations together with machine learning extrapolation methods. An extension to radius differences further allows us to investigate a potential proton halo in $^{8}$ B and, moreover, provide predictions that relate directly to the isotope shift, which can be precisely measured in experiments.
nucl-thPRC(2025)·8 citations
05
Exploiting $ν$ -dependence of projected energy correlators in HICs
Ankita Budhraja🇳🇱 · Balbeer Singh🇺🇸
We extend the recently derived factorization formula for energy-energy correlators to study the analytic structure of general $ν$ -point projected energy correlators in heavy ion collisions. The $ν$ -point projected energy correlators (or, $ν$ -correlators) are an analytically continued family of the integer $N$ -point projected energy correlators, which probe correlations between $N$ final-state particles. By tracking the largest separation ( $χ$ ) between the $N$ particles, in vacuum, their structure is closely related to the DGLAP splitting functions and exhibits a classical scaling behavior $\sim 1/ χ$ which is modified by resummation through the anomalous dimensions. We show that, in a thermal medium, the $ν$ -correlators display non-trivial angular scaling already at the leading order in perturbation theory. We find that for non-integer values, particularly $ν < 1$ , medium-induced jet function is enhanced compared to $ν > 1$ . This is particularly manifested in the ratios of $ν$ -correlators with respect to the two-point energy correlator which encode an intrinsic angular information for $ν < 1$ when compared to large $ν$ values. Moreover, for small- $ν$ values, the $ν$ -correlators appear to saturate at $ν = 0.01$ . We further confirm our leading-order numerical computations against simulated events from JEWEL for the parton level production cross-section. Finally, we qualitatively discuss the effect of BFKL resummation for various values of $ν$ .
↳ hep-phnucl-exnucl-thPLB(2026)·10 citations
06
Nucleon Energy Correlators for the Odderon
Heikki Mäntysaari🇫🇮 · Yossathorn Tawabutr🇫🇮 · Xuan-Bo Tong🇫🇮
We investigate the T-odd nucleon energy correlator (NEC) at small $x$ and establish its connection with the spin-dependent odderon. Probing the T-odd NEC involves measuring a single transverse spin asymmetry (SSA) for the energy pattern in the target fragmentation region in deep inelastic scattering. We find that while the inclusive energy pattern results in a vanishing SSA, a nonzero SSA emerges when restricting the measurement to charged hadrons, which are directly measured in tracking detectors. To describe this effect, we introduce the track-based NEC and evaluate its small- $x$ limit from fracture functions using the energy sum rule. The resulting SSA exhibits an opposite sign between positively and negatively charged hadrons, providing a clear experimental signature of the odderon. Furthermore, by incorporating charge weighting into the NEC, we construct a C-odd tag in the final state, eliminating potential contamination from C-even gluonic contributions. Our results demonstrate that these track-based energy-pattern observables offer a clean and sensitive probe for unveiling odderon dynamics at the future electron-ion collider.
↳ hep-phnucl-thPRD(2025)·21 citations
07
Proton Spin Decomposition via QCD Sum Rules
HyungJoo Kim🇯🇵 · Philipp Gubler🇯🇵 · Chihiro Sasaki🇯🇵
We present a novel approach for investigating the spin structure of hadrons based on the two-point function in quantum field theory. In a rotating frame, we derive two independent expressions of the two-point function and identify their equivalence, which allows for a complete decomposition of the total spin of a composite system into the angular momenta of its constituent particles. Applying this approach to the proton, we analyze its spin structure in the massless quark limit. Our results indicate that the quark spin contribution accounts for approximately 27 $%$ of the total proton spin at a low-energy scale, significantly deviating from the prediction of the non-relativistic quark model.
↳ hep-phnucl-thPLB(2025)·2 citations
08
Effect of $α$ -clusters on particle production in O $-$ O and p $-$ O collisions at LHC energies
Deependra Sharma🇮🇳 · Arpit Singh🇮🇳 · Md. Samsul Islam🇮🇳 · Basanta Nandi🇮🇳 · Sadhana Dash🇮🇳
In the present work, O $-$ O collisions at $s_{N N}$ = 7 TeV and p $-$ O collisions at $s_{N N}$ = 9.9 TeV are studied using PYTHIA8/Angantyr model for heavy-ion collisions. The theoretically predicted $α$ -cluster structure of oxygen nucleus is implemented in the model to investigate the effect of initial configuration of oxygen nucleus on final state observables. The results obtained from $α$ -cluster structure are compared with those obtained from Woods-Saxon nuclear charge density distribution. The Angantyr model simulation showed that the radial distribution of oxygen nucleus in $α$ -cluster configuration is more compact in comparison to the Woods-Saxon distribution. The results on charged and identified particle pseudorapidity distribution is obtained in the two initial state configuration of the oxygen nucleus. The results demonstrated that the effect of initial geometrical configuration is more distinct in the non-central collisions in comparison to the central collisions for both O $-$ O and p $-$ O collisions.
↳ hep-phnucl-thPRC(2025)·9 citations
09
Experimental Signatures for Identifying Distinct Origins of Color Field Generation
Subramanya Bhat K. N.🇮🇳 · Amita Das🇮🇳 · Bhooshan Paradkar🇮🇳 · V Ravishankar🇮🇳
Signatures for non-abelian dynamics have long been central to QCD and QGP. Equally important are they in spin systems and laser-plasma interactions, where they emerge as effective interactions. Distinguishing experimentally gauge inequivalent sources (and hence potentials) that produce the same field tensor is one major task in this endeavour. As a step in this direction, this paper investigates how physically distinct sources which produce the same color electric field (uniform and constant) may be distinguished experimentally in a gauge-invariant manner. We first study the motion of a test particle in such fields and show that the resultant trajectories are counterintuitive. We then examine the radiation emitted - both gluonic and photonic and show that each source (independent non-abelian configuration) leaves a unique signature in the energy spectra, laying the ground for application to specific physical systems.
↳ physics.plasm-phcond-mat.otherhep-phhep-th+1New J.Phys.(2025)·1 citation
10
Chiral Solitons
Herbert Weigel🇿🇦
Generalizing quantum chromodynamics (QCD) from three to arbitrarily many color degrees of freedom suggests that baryons can be described as solitons in an effective meson theory whose interaction strength decreases with the number of colors. The exact form of that theory is unknown, but at low energies chiral symmetry and its breaking are considered as the construction recipes for modeling the theory. The Skyrmion is a static, localized solution in a non-linear field theory for pions and it is the most prominent version of a soliton in a chirally symmetric meson theory. Upon quantization it reproduces the spectrum of the low-lying baryons and their static properties reasonably well. Extending that theory by vector mesons improves on the agreement between predicted and empirical data. Chiral solitons within models for the quark flavor dynamics facilitate the investigation of nucleon structure functions. Here we provide a pedagogical overview of these facets.
↳ hep-phhep-thnucl-th0 citations
11
Quantum decoherence in the Caldeira-Leggett model by the real-time path integral on a computer
Jun Nishimura🇯🇵 · Hiromasa Watanabe🇯🇵
We propose first-principle calculations of an open system based on the real-time path integral formalism treating the environment as well as the system of our interest together on a computer. The sign problem that occurs in applying Monte Carlo methods can be overcome in general by using the so-called Lefschetz thimble method, which has been developed over the past decade. Here we focus on the Caldeira-Leggett model, which is well known, in particular, as a model of quantum decoherence. In this case, the calculation simplifies drastically since the path integral becomes Gaussian for typical initial conditions. The relevant saddle point, which is unique and complex, can be determined by solving a linear equation with a huge but sparse coefficient matrix, and the integration over the Lefschetz thimble can be performed analytically. Thus we obtain, without assumptions or approximations, the reduced density matrix after a long-time evolution, tracing out a large number of harmonic oscillators in the environment. In particular, we confirm the dependence of the decoherence time on the coupling constant and the temperature that has been predicted from the master equation in a certain parameter regime.
↳ hep-latcond-mat.stat-mechhep-thnucl-th+1JHEP(2025)·4 citations
12
Feasibility of measuring the speed of sound of the quark-gluon plasma from the multiplicity and mean $p_{T}$ of ultracentral heavy-ion collisions
Lorenzo Gavassino🇺🇸 · Henry Hirvonen🇺🇸 · Jean-François Paquet🇺🇸 · Mayank Singh🇺🇸 · Gabriel Soares Rocha🇺🇸
The mean transverse momentum $⟨ p_{T} ⟩$ of hadrons has been observed experimentally and in numerical simulations to have a power-law dependence on the hadronic multiplicity $N$ in ultracentral relativistic heavy-ion collisions: $⟨ p_{T} ⟩ \propto N^{b_{UC}}$ . It has been put forward that this exponent $b_{UC}$ is the speed of sound of quark-gluon plasma measured at a temperature determined from $⟨ p_{T} ⟩$ . We study step by step the connection between (i) the energy and entropy of hydrodynamic simulations and (ii) experimentally measurable observables. We show that an argument based on energy and entropy should yield an exponent equal to the pressure over energy density $P / ε$ , rather than the speed of sound $c_{s}^{2}$ ; however, we also observe that $⟨ p_{T} ⟩$ and $N$ are not sufficiently accurate proxies for the energy and entropy to make this possible in practice. From simulations, we find that the exponent $b_{UC}$ is significantly different whether the ''effective volume'' is strictly constant or not, a condition that cannot be enforced experimentally. Additional tests using a modified equation of state find that the exponent $b_{UC}$ exhibits a variable degree of correlations with the speed of sound and with $P / ε$ , but is not an accurate measurement of either quantity in general.
↳ hep-phnucl-thPRC(2025)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE