Nuclear Theory·nucl-th

Thursday·November 14, 2024

14 papers—9 primary·5 cross-listed

10
[Submitted on 12 Nov 2024] (cross-list from hep-ph)
Precision evaluation of the $η$ - and $η^{'}$ -pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon
Simon Holz🇨🇭 · Martin Hoferichter🇨🇭 · Bai-Long Hoid🇨🇭 · Bastian Kubis🇩🇪
Next to the $π^{0}$ pole, $η$ and $η^{'}$ intermediate states give rise to the leading singularities of the hadronic light-by-light tensor, resulting in sizable contributions to the anomalous magnetic moment of the muon $a_{μ}$ . The strength of the poles is determined by the respective transition form factors (TFFs) to two (virtual) photons. We present a calculation of these TFFs that implements a number of low- and high-energy constraints, including the $η^{(')} \to γ γ$ decay widths, $η^{(')} \to π^{+} π^{-} γ$ spectra, chiral symmetry for the $η^{(')} \to 2 (π^{+} π^{-})$ amplitudes, vector-meson couplings, and asymptotic limits. Crucially, we investigate the role of the leading left-hand singularity generated by the exchange of the $a_{2}$ tensor meson, yielding, for the first time, an estimate of the associated factorization-breaking corrections. Our final results, $a_{μ}^{η -pole} = 14.7 (9) \times 1 0^{- 11}$ and $a_{μ}^{η^{'} -pole} = 13.5 (7) \times 1 0^{- 11}$ , conclude a dedicated effort to evaluate the pseudoscalar-pole contributions to hadronic light-by-light scattering using dispersion relations, amounting to a combined $a_{μ}^{PS-poles} = 91. 2_{- 2.4}^{+ 2.9} \times 1 0^{- 11}$ .
Comments:
8 pages, 3 figures, version published in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2411.08098 [pdf]
PRL(2025)·45 citations
11
[Submitted on 12 Nov 2024] (cross-list from hep-ph)
Spin dynamics with realistic hydrodynamic background for relativistic heavy-ion collisions
Sushant K. Singh🇮🇹 · Radoslaw Ryblewski🇵🇱 · Wojciech Florkowski🇵🇱
The equations of perfect spin hydrodynamics are solved for the first time using a realistic (3+1)-dimensional hydrodynamic background, calibrated to reproduce a comprehensive set of hadronic observables, including rapidity distributions, transverse momentum spectra, and elliptic flow coefficients for Au+Au collisions at the beam energy of $s_{NN} = 200$ GeV. The spin dynamics is governed by the conservation of the spin tensor, describing spin- $\frac{1}{2}$ particles, with particle mass in the spin tensor treated as an effective parameter. We investigate several scenarios, varying both the effective mass and the initial evolution time for the spin polarization tensor. The model predictions are then compared with experimental measurements of global and longitudinal spin polarization of Lambda hyperons. Our results indicate that a successful description of the data requires a delayed initial evolution time for the perfect spin hydrodynamics of about 4 fm/ $c$ (in contrast to the standard initial time of 1 fm/ $c$ used for the hydrodynamic background). This delay marks a transition from the phase where spin-orbit interaction is significant to the regime where spin-conserving processes dominate. Our findings suggest that the spin-orbit dissipative interaction plays a significant role only in the very early stages of the system's evolution.
Comments:
19 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2411.08223 [pdf]
PRC(2025)·32 citations
12
[Submitted on 13 Nov 2024] (cross-list from hep-ph)
Hypernuclei production with a modified coalescence model in BUU transport calculations
Gabor Balassa🇰🇷 · Gyorgy Wolf🇭🇺
In this paper, the usual momentum- and coordinate-space distance criteria for creating nuclear clusters in transport simulations are addressed by using a dynamical, covariant description in an off-shell Boltzmann-Uehling-Uhlenbeck transport approach. The free parameter of this clustering scheme is the cluster formation time, which is fitted through the FOPI data of low energy charged cluster multiplicities in Au+Au collisions at 150 A MeV and 400 A MeV incident energies. The coalescence model is used to estimate the yields of the 3H(Lambda), 5H(2Lambda), 6He(2Lambda) single and double strange hypernuclei in central Au+Au collisions between 2, and 20 A GeV incident energies, giving comparable results to estimations from other methods.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2411.08379 [pdf]
EPJA(2023)·3 citations
13
[Submitted on 13 Nov 2024] (cross-list from hep-ph)
The time evolution of light nuclei cumulants and ratios with a first-order phase transition in the UrQMD transport model
Thiranat Bumnedpan🇩🇪 · Jan Steinheimer🇩🇪 · Tom Reichert🇩🇪 · Christoph Herold🇹🇭 · Ayut Limphirat🇹🇭 · Marcus Bleicher🇩🇪
The UrQMD model with a density dependent equation of state, including a first-order phase transition, is used to study the time dependence of baryon number and proton number susceptibilities up to third order in heavy ion reactions of $E_{lab} = 2 - 3 A$ GeV. A significant deviation from the Gaussian fluctuations of the baryon number fluctuation in coordinate space is observed. The proton number fluctuations are always suppressed as they constitute only a small fraction of the total baryon number during the dense phase of the collision. It is found that the only measurable, but small, signal would be an enhancement of the third order (or higher) proton cumulant in a finite rapidity window $Δ y$ that is larger than one unit of rapidity. In addition, it is found that the coordinate fluctuations will lead to an enhancement of cluster production due to the correlations in coordinate space. However, this enhancement is small and mainly occurs during the dense part of the collision before the system actually freezes out.
Comments:
9 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2411.08444 [pdf]
PRC(2025)·2 citations
14
[Submitted on 13 Nov 2024] (cross-list from gr-qc)
Dark energy effects on realistic neutron stars
Juan M. Z. Pretel🇧🇷 · Sergio B. Duarte🇧🇷 · José D. V. Arbañil🇵🇪 · Mariana Dutra🇧🇷 · Odilon Lourenço🇧🇷
By considering realistic equations of state (EoSs) to describe the ordinary matter of the stellar crust, in this study, we explore the effect of a dark energy core, made of Chaplygin Dark Fluid (CDF), on neutron stars (NSs). To accomplish this purpose, we solve the stellar structure equations and investigate the impact of the CDF parameters on the several macroscopic properties of NSs such as mass-radius ( $M - R$ ) relation, and tidal deformabilities of a single star and of a binary system, the latter being of great importance when analyzing gravitational-wave signals coming from the merger of such compact objects. We also present an analysis of the radial oscillation modes for the rapid phase transition, with the aim of distinguishing regions consisting of dynamically stable stars from those of unstable ones. Specifically, our outcomes reveal that an increase in the energy density jump (controlled by a parameter $α$ ) leads to an increase in the radial stability of the NS with a CDF core. Furthermore, our theoretical results are consistent with the observational $M - R$ measurements of millisecond pulsars from NICER data and tidal deformability constraints from the GW170817 event.
Comments:
12 pages, 7 figures and 3 tables
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2411.08793 [pdf]
PRD(2024)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Precision evaluation of the η- and η′-pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon

Spin dynamics with realistic hydrodynamic background for relativistic heavy-ion collisions

Hypernuclei production with a modified coalescence model in BUU transport calculations

The time evolution of light nuclei cumulants and ratios with a first-order phase transition in the UrQMD transport model

Dark energy effects on realistic neutron stars

Affiliations

Precision evaluation of the $η$ - and $η^{'}$ -pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon