Nuclear Theory·nucl-th

Tuesday·May 13, 2025

19 papers—13 primary·6 cross-listed

14
Multiprocess imaging of nuclear modifications on parton distributions in proton-nucleus collisions
Meng-Quan Yang🇨🇳 · Peng Ru🇨🇳 · Ben-Wei Zhang🇨🇳
Nuclear modifications to collinear parton distribution functions are conventionally quantified by the ratios $r_{i}^{A} (x, Q^{2}) = f_{i}^{A,proton} (x, Q^{2}) / f_{i}^{proton} (x, Q^{2})$ . For a given nucleus $A$ , these ratios generally depend on the parton momentum fraction $x$ , the probing scale $Q^{2}$ , and the parton species $i$ . Determining these dependencies relies on a global analysis of diverse experimental data. However, in realistic observables, these dependencies are intricately intertwined, making their extraction challenging. In this paper, we propose a novel approach to effectively image the nuclear modification factors $r_{i}^{A} (x, Q^{2})$ at the observable level in proton-nucleus collisions at the Large Hadron Collider. Specifically, through a combined study of $Z$ -boson production, $Z$ +jet production, and $Z + c$ -jet production, we separately enhance signals arising from light-quark, gluon, and heavy-flavor (charm) distributions in nuclei. This enables us to effectively image the $r_{i}^{A} (x, Q^{2})$ for specific parton species. The feasibility of this method is validated through perturbative calculations at next-to-leading order in the strong coupling constant, employing three sets of nuclear PDF parametrizations: EPPS21, nCTEQ15, and TUJU19. Future measurements of these observables are expected to provide more efficient constraints on nuclear PDFs and yield new insights into the detailed partonic structures of nuclei.
↳ hep-phnucl-thPRD(2025)·2 citations
15
On the validity of the complex Langevin method near the deconfining phase transition in QCD at finite density
Shoichiro Tsutsui🇯🇵 · Yuhma Asano🇯🇵 · Yuta Ito🇯🇵 · Hideo Matsufuru🇯🇵 · Yusuke Namekawa🇯🇵 · Jun Nishimura🇯🇵 · Shinji Shimasaki🇯🇵 · Asato Tsuchiya🇯🇵
In our previous paper [JHEP 10 (2020) 144], we found that the complex Langevin (CL) method works for QCD at finite density on the $1 6^{3} \times 32$ lattice in the low-temperature high-density regime within the range $μ / T = 1.6 - 9.6$ with $μ$ and $T$ being the quark chemical potential and the temperature, which enabled us to see a clear trend towards the formation of the Fermi sphere. Here we investigate the validity of the CL method on the $2 4^{3} \times 12$ lattice in the deconfined phase near the deconfinement phase transition. As before, we use four-flavor staggered fermions and judge the validity using the criterion based on the probability distribution of the drift term. The spatial extent is $L = (1.3 - 2.7 fm) > Λ_{LQCD}^{- 1} \sim 1 fm$ , in contrast to our previous study with $L < Λ_{LQCD}^{- 1}$ . We find that the CL method works in a broad region up to $μ / T = 4.8$ , while it starts to fail as we approach the phase boundary due to the singular drift problem, which can be understood qualitatively by extending the Banks-Casher relation to the case at finite density.
↳ hep-latcond-mat.stat-mechhep-thnucl-thJHEP(2025)·6 citations
16
Pseudoscalar Meson Parton Distributions Within Gauge-Invariant Nonlocal Chiral Quark Model
Parada T. P. Hutauruk🇰🇷
In this paper, I investigate the gluon distributions for the kaon and pion, as well as the improvement of the valence-quark distributions, in the framework of the gauge-invariant nonlocal chiral quark model (NL $χ$ QM), where the momentum dependence is taken into account. I then compute the gluon distributions for the kaon and pion that are dynamically generated from the splitting functions in the DGLAP QCD evolution. In a comparison with the recent lattice QCD and JAM global analysis results, it is found that the results for the pion gluon distributions at $Q =$ 2 GeV, which is set based on the lattice QCD, have a good agreement with the recent lattice QCD data; this is followed up with the up valence-quark distribution of the pion results at $Q =$ 5.2 GeV in comparison with the reanalysis experimental data. The prediction for the kaon gluon distributions at $Q = 2$ GeV is consistent with the recent lattice QCD calculation.
↳ hep-phnucl-thSymmetry(2025)·6 citations
17
$ϕ$ meson properties in dense resonance matter at finite temperature
Manpreet Kaur🇮🇳 · Arvind Kumar🇮🇳
The effective mass and decay width of the $ϕ$ meson in the isospin asymmetric hot and dense resonance matter are studied using the effective Lagrangian framework considering the $ϕ K K ˉ$ interactions at one-loop level. In addition to spin $- 1/2$ octet baryons, we consider the effect of resonances $Δ^{++, +, 0, -}, Σ^{*\pm, 0}, Ξ^{* 0, -}, Ω^{-}$ , on the properties of $ϕ$ meson. The in-medium effects on the $ϕ$ meson properties are simulated through the effective masses of kaons and antikaons computed using the chiral SU(3) hadronic mean field model in the presence of resonance baryons. The loop integral appearing in the computation of $ϕ$ meson self energies is regularized using the dipole form factor with a cutoff parameter. The presence of resonance baryons within the medium at finite temperature is observed to significantly modify the effective mass and decay width of $ϕ$ mesons. Examining the $ϕ$ meson masses and decay width within a dense medium is anticipated to be essential for understanding experimental results from heavy-ion collision experiments.
↳ hep-phnucl-thPRD(2025)·5 citations
18
Enhancement of photon emission rate near QCD critical point
Yukinao Akamatsu🇯🇵 · Masayuki Asakawa🇯🇵 · Masaru Hongo🇯🇵 · Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸
We compute photon emission rate enhancement near the QCD critical point using an effective theory of dynamic critical phenomena and derive a universal photon spectrum. The emission rate scales similarly to conductivity, increasing with the correlation length ( $ξ$ ), diverging at the critical point. The spectrum exhibits $ω d N_{γ} / d^{3} k \propto ω^{- 1/2}$ in the scaling regime, with the transition occurring at a frequency comparable to shear damping rate $ω \sim γ_{η} / ξ^{2}$ , reflecting the nonequilibrium properties of the near-critical liquid.
↳ hep-phcond-mat.stat-mechhep-thnucl-ex+1PRD(2026)·4 citations
19
Training neural control variates using correlated configurations
Hyunwoo Oh🇺🇸
Neural control variates (NCVs) have emerged as a powerful tool for variance reduction in Monte Carlo (MC) simulations, particularly in high-dimensional problems where traditional control variates are difficult to construct analytically. By training neural networks to learn auxiliary functions correlated with the target observable, NCVs can significantly reduce estimator variance while preserving unbiasedness. However, a critical but often overlooked aspect of NCV training is the role of autocorrelated samples generated by Markov Chain Monte Carlo (MCMC). While such samples are typically discarded for error estimation due to their statistical redundancy, they may contain useful information about the structure of the underlying probability distribution that can benefit the training process. In this work, we systematically examine the effect of using correlated configurations in training neural control variates. We demonstrate, both conceptually and numerically, that training on correlated data can improve control variate performance, especially in settings with limited computational resources. Our analysis includes empirical results from $U (1)$ gauge theory and scalar field theory, illustrating when and how autocorrelated samples enhance NCV construction. These findings provide practical guidance for the efficient use of MCMC data in training neural networks.
↳ hep-latcs.LGnucl-thPRD(2025)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Multiprocess imaging of nuclear modifications on parton distributions in proton-nucleus collisions

On the validity of the complex Langevin method near the deconfining phase transition in QCD at finite density

Pseudoscalar Meson Parton Distributions Within Gauge-Invariant Nonlocal Chiral Quark Model

ϕ meson properties in dense resonance matter at finite temperature

Enhancement of photon emission rate near QCD critical point

Training neural control variates using correlated configurations

Affiliations

$ϕ$ meson properties in dense resonance matter at finite temperature