Nuclear Theory·nucl-th

Monday·December 16, 2024

10 papers—5 primary·5 cross-listed

01
[Submitted on 12 Dec 2024]
Effective temperatures of the QGP from thermal photon and dilepton production
Olaf Massen🇳🇱 · Govert Nijs🇨🇭 · Mike Sas🇳🇱 · Wilke van der Schee🇳🇱 · Raimond Snellings🇳🇱
Thermal electromagnetic radiation is emitted by the quark-gluon plasma (QGP) throughout its space-time evolution, with production rates that depend characteristically on the temperature. We study this temperature using thermal photons and dileptons using the Trajectum heavy ion code, which is constrained by Bayesian analysis. In addition we present the elliptic flow of both the thermal photons and thermal dileptons including systematic uncertainties corresponding to the model parameter uncertainty. We give a comprehensive overview of the resulting effective temperatures $T_{eff}$ , obtained from thermal photon transverse momentum and thermal dilepton invariant mass distributions, as well as the dependence of $T_{eff}$ on various selection criteria of these probes. We conclude that the $T_{eff}$ obtained from thermal photons is mostly insensitive to the temperature of the QGP with a value of $T_{eff} \sim$ 250-300 MeV depending on their transverse momentum, almost independent of collision centrality. Thermal dileptons are much better probes of the QGP temperature as they do not suffer from a blue shift as their invariant mass is used, allowing for a more precise constraint of the QGP temperature during different stages of the evolution of the system. By applying selection criteria on the dilepton transverse momentum and the invariant mass we are able to extract fluid temperatures on average times ranging from late emission ( $⟨ τ ⟩ = 5.6$ fm $/ c$ ) to very early emissions ( $⟨ τ ⟩ < 1.0$ fm $/ c$ ). Furthermore, we show how these selection criteria can be used to map the elliptic flow of the system all throughout its evolution.
Comments:
13 pages, 13 figures. The Trajectum code can be found at https://sites.google.com/view/govertnijs/trajectum and plotting routines can be found at http://wilkevanderschee.nl/trajectum
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2412.09671 [pdf]
EPJC(2025)·17 citations
02
[Submitted on 12 Dec 2024]
Deuteron- $^{3} He$ scattering using nucleon- $^{3} He$ optical potentials fitted to four-body amplitudes
A. Deltuva · D. Jurčiukonis
Deuteron- $^{3} He$ reactions in the 15 to 40 MeV range are studied using a three-body model where the constructed nonlocal optical potentials rely on rigorous nucleon- $^{3} He$ scattering calculations. The differential cross section for the elastic scattering and neutron transfer reaction is predicted quite well up to 90 deg scattering angles. The importance of the Pauli term in complex potentials is demonstrated.
Comments:
7+2 pages, 5+2 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2412.09703 [pdf]
PLB(2025)·0 citations
03
[Submitted on 13 Dec 2024]
Improving the predictive power of empirical shell-model Hamiltonians
J. A. Purcell · B. A. Brown · B. C. He · S. R. Stroberg · W. B. Walters
We present two developments which enhance the predictive power of empirical shell-model Hamiltonians for cases in which calibration data are sparse. A recent improvement in the ab initio derivation of effective Hamiltonians leads to a much better starting point for the optimization procedure. In addition, we introduce a protocol to avoid overfitting, enabling a more reliable extrapolation beyond available data. These developments will enable more robust predictions for exotic isotopes produced at rare isotope beam facilities and in astrophysical environments.
Comments:
12 pages, 27 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2412.09917 [pdf]
PRC(2025)·5 citations
04
[Submitted on 13 Dec 2024]
Relativistic Viscous Hydrodynamics in the Density Frame: Numerical Tests and Comparisons
Jay Bhambure🇺🇸 · Aleksas Mazeliauskas🇩🇪 · Jean-Francois Paquet🇺🇸 · Rajeev Singh🇷🇴 · Mayank Singh🇺🇸 · Derek Teaney🇺🇸 · Fabian Zhou🇩🇪
We conduct a numerical study of relativistic viscous fluid dynamics in the Density Frame for one-dimensional fluid flows. The Density Frame is a formulation of relativistic viscous hydrodynamics that is first-order in time, requires no auxiliary fields, and has no non-hydrodynamic modes. We compare our results to QCD kinetic theory simulations and find excellent agreement within the regime of applicability of hydrodynamics. Additionally, the Density Frame results remain well-behaved and robust near the boundary of applicability. We also compare our findings to the second-order-in-time hydrodynamic theory developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK) and a well-known Müller-Israel-Stewart-type hydrodynamics code, MUSIC, which is commonly used to simulate heavy-ion collisions.
Comments:
28 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
2412.10303 [pdf]
PRC(2025)·24 citations
05
[Submitted on 13 Dec 2024]
Stochastic relativistic viscous hydrodynamics from the Metropolis algorithm
Jay Bhambure🇺🇸 · Rajeev Singh🇷🇴 · Derek Teaney🇺🇸
We propose an algorithm for simulating stochastic relativistic fluid dynamics based on Metropolis updates. Each step of the algorithm begins with an update based on ideal hydrodynamics. This is followed by proposing random (spatial) momentum transfers between fluid cells, keeping the total energy fixed. These proposals are then accepted or rejected using the change in entropy as a statistical weight. The algorithm reproduces relativistic viscous hydrodynamics in the ``Density Frame", which is a formulation of viscous hydrodynamics we review and clarify here. This formulation is first order in time and requires no auxiliary dynamical fields such as $Π^{μν}$ . The only parameters are the shear and bulk viscosities and the equation of state. By adopting the 3+1 split of general relativity, we extend the Metropolis algorithm to general space-time coordinates, such as Bjorken coordinates, which are commonly used to simulate heavy-ion collisions.
Comments:
31 pages, 1 figure; v2 fixes typo
Subjects:
Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Theory (hep-th)
arXiv:
2412.10306 [pdf]
PRC(2025)·21 citations
06
[Submitted on 12 Dec 2024] (cross-list from hep-ph)
Quantum stresses in the hydrogen atom
Adam Freese🇺🇸
Gravitational form factors are often interpreted as providing access to stresses inside hadrons, in particular through Fourier transforms of the form factors $D$ and $c ˉ$ . Some researchers, however, have expressed skepticism of this interpretation. I revisit the question, and argue that it is indeed appropriate to interpret these quantities as stress distributions. I consider the hydrogen atom's ground state as a familiar example, and use the pilot wave interpretation of quantum mechanics to give the distributions a clear meaning. A striking result is that $c ˉ$ -- rather than $D$ -- quantifies the force law binding the system, which can be understood through Cauchy's first law of motion.
Comments:
17 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2412.09664 [pdf]
PRD(2025)·15 citations
07
[Submitted on 13 Dec 2024] (cross-list from hep-ph)
In-medium electromagnetic form factors of pseudoscalar mesons from the quark model
Ahmad Jafar Arifi🇯🇵 · Parada T. P. Hutauruk🇰🇷 · Kazuo Tsushima🇧🇷
We explore the modifications of hadron structure in a nuclear medium, focusing on the spacelike electromagnetic form factors (EMFFs) of light and heavy-light pseudoscalar mesons. By combining the light-front quark model (LFQM) with the quark-meson coupling (QMC) model, which reasonably reproduces EMFFs in free space and the saturation properties of nuclear matter, respectively, we systematically analyze the in-medium EMFFs and charge radii of mesons with various quark flavors. Our findings show that the EMFFs of charged (neutral) mesons exhibit a faster fall-off (increase) with increasing four-momentum transfer squared and nuclear density. Consequently, the absolute value of the charge radii of mesons increases with nuclear density, where the rate of increase depends on their quark flavor contents. We observe that the EMFFs of pions and kaons undergo significant modifications in the nuclear medium, while heavy-light mesons are only slightly modified. By decomposing the quark flavor contributions to EMFFs, we show that the medium effects primarily impact the light-quark sector, leaving the heavy-quark sector nearly unaffected. The results of this study further suggest the importance of the medium effects at the quark level.
Comments:
16 pages, 9 figures, 4 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2412.09883 [pdf]
PRD(2025)·8 citations
08
[Submitted on 13 Dec 2024] (cross-list from hep-ph)
Photon-induced neutron, proton and alpha evaporation from heavy nucleus
P. Jucha · K. Mazurek · M. Klusek-Gawenda · M. Ciemala · A. Szczurek · Yuliia Shevchuk · S. Słotwiński
In ultraperipheral heavy-ion collisions (UPCs) at the Large Hadron Collider (LHC) Pb nuclei are excited through interactions induced by strong electromagnetic fields. The expected excitation energy could reach hundreds MeV, which leads to the subsequent emission of various particles, including neutrons, protons, and alpha particles. To accurately describe deexcitation of nuclei, we have developed two novel approaches. The first method utilizes the Heavy Ion Phase Space Exploration (HIPSE) model to simulate pre-equilibrium emissions and to estimate the excitation energy of the remaining nucleus. Our second approach introduces a new technique for modeling the excitation energy of the nucleus. This method consists of a two-component function to represent the excitation energy distribution more precisely, accounting for the energy loss due to the interaction between photons and quasi-deuteron. Both of these modeling techniques are integrated with the results produced by the GEMINI++ generator, which implements the Hauser-Feshbach formalism to simulate the statistical decay of excited nuclei. The alternative calculations are done with EMPIRE platform. Using these approaches, we obtained the cross sections for the emission of neutrons, protons, and alpha particles resulting from UPC at the LHC. Our results were compared with the experimental data of the ALICE group on neutron and proton multiplicities.
Comments:
7 pages, Presented at the 57th Zakopane Conference on Nuclear Physics, "Extremes of the Nuclear Landscape", Zakopane, Poland, 25 August-1 September, 2024
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2412.10100 [pdf]
Acta Phys.Polon.Supp.(2025)·1 citation
09
[Submitted on 13 Dec 2024] (cross-list from astro-ph.HE)
Equation of State Independent Determination on the Radius of a 1.4 $M_{⊙}$ Neutron Star Using Mass-Radius Measurements
Chun Huang
Traditional methods for determining the radius of a 1.4 $M_{⊙}$ neutron star ( $R_{1.4}$ ) rely on specific equations of state (EOS) models that describe various types of dense nuclear matter. This dependence on EOS models can introduce substantial systematic uncertainties, which may exceed the measurement uncertainties when constraining $R_{1.4}$ . In this study, we explore a novel approach to constraining $R_{1.4}$ using data from NICER observations of PSR J0030+0451 (J0030) and PSR J0437-4715 (J0437). However, this work presents a more data-driven analysis framework, substantially decreasing the need for EOS assumptions. By analyzing the Mass-Radius measurements of these two neutron stars, we infer $R_{1.4}$ using statistical methods based mostly on observational data. We examine various hotspot configurations for J0030, along with new J0437 observations, and their effects on the inferred radius. Our results are consistent with X-ray timing, gravitational wave, and nuclear physics constraints, while avoiding EOS-related biases. The same method has also been applied to a simulated mass-radius dataset, based on our knowledge of future X-ray telescopes, demonstrating the model's ability to recover the injected $R_{1.4}$ value in certain cases. This method provides a data-driven pathway for extracting neutron star properties and offers a new approach for future observational efforts in neutron star astrophysics.
Comments:
Published version in ApJ Letters
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2412.10242 [pdf]
ApJL(2025)·8 citations
10
[Submitted on 13 Dec 2024] (cross-list from hep-ph)
Toward a foundation model for heavy-ion collision experiments based on point-cloud diffusion
Manjunath Omana Kuttan🇩🇪 · Kai Zhou🇩🇪 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪
A novel point cloud diffusion model for relativistic heavy-ion collisions, capable of ultra-fast generation of complete, event-by-event collision output, is introduced. When trained on UrQMD cascade simulations, the model generates realistic collision event output containing 26 distinct hadron species, as a list of particle momentum vectors along with their particle ID. From solving inverse problems to accelerating model calculations or detector simulations, the model can be a promising general purpose tool for heavy-ion collisions beneficial to both theoretical studies and experimental applications.
Comments:
Matches published version. 8 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2412.10352 [pdf]
PRC(2025)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE