Nuclear Theory·nucl-th

Monday·December 20, 2021

12 papers—7 primary·5 cross-listed

08
Concerning pion parton distributions
Z.-F. Cui🇨🇳 · M. Ding🇩🇪 · J. M. Morgado🇪🇸 · K. Raya🇪🇸 · D. Binosi🇮🇹 · L. Chang🇨🇳 · J. Papavassiliou🇪🇸 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸 · S. M. Schmidt🇩🇪
Analyses of the pion valence-quark distribution function (DF), $u^{π} (x; ζ)$ , which explicitly incorporate the behaviour of the pion wave function prescribed by quantum chromodynamics (QCD), predict $u^{π} (x ≃ 1; ζ) \sim (1 - x)^{β (ζ)}$ , $β (ζ ≳ m_{p}) > 2$ , where $m_{p}$ is the proton mass. Nevertheless, more than forty years after the first experiment to collect data suitable for extracting the $x ≃ 1$ behaviour of $u^{π}$ , the empirical status remains uncertain because some methods used to fit existing data return a result for $u^{π}$ that violates this constraint. Such disagreement entails one of the following conclusions: the analysis concerned is incomplete; not all data being considered are a true expression of qualities intrinsic to the pion; or QCD, as it is currently understood, is not the theory of strong interactions. New, precise data are necessary before a final conclusion is possible. In developing these positions, we exploit a single proposition, viz. there is an effective charge which defines an evolution scheme for parton DFs that is all-orders exact. This proposition has numerous corollaries, which can be used to test the character of any DF, whether fitted or calculated.
↳ hep-phhep-exhep-latnucl-ex+1EPJA(2022)·57 citations
09
Alpha-alpha scattering in the Multiverse
Serdar Elhatisari🇹🇷 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪 · Thomas Vonk🇩🇪
We investigate the phase shifts of low-energy alpha-alpha scattering under variations of the fundamental parameters of the Standard Model, namely the light quark mass, the electromagnetic fine-structure constant as well as the QCD theta-angle. As a first step, we recalculate alpha-alpha scattering in our Universe utilizing various improvements in the adiabatic projection method, which leads to an improved, parameter-free prediction of the S- and D-wave phase shifts for laboratory energies below 10 MeV. We find that positive shifts in the pion mass have a small effect on the S-wave phase shift, whereas lowering the pion mass adds some repulsion in the two-alpha system. The effect on the D-wave phase shift turns out to be more pronounced as signaled by the D-wave resonance parameters. Variations of the fine-structure constant have almost no effect on the low-energy alpha-alpha phase shifts. We further show that up-to-and-including next-to-leading order in the chiral expansion, variations of these phase shifts with respect to the QCD theta-angle can be expressed in terms of the theta-dependent pion mass.
↳ hep-thastro-ph.COhep-lathep-ph+1JHEP(2022)·17 citations
10
Thermal freeze-out parameters and pseudo-entropy from charged hadron spectra in high energy collisions
Xu-Hong Zhang🇨🇳 · Ya-Qin Gao🇨🇳 · Fu-Hu Liu🇨🇳 · Khusniddin K. Olimov🇺🇿
We collected the transverse momentum (mass) spectra of charged hadrons ( $π^{-}$ , $π^{+}$ , $K^{-}$ , $K^{+}$ , $p$ , and $p$ ) produced in collisions over a center-of-mass energy range from 2.70 to 200 GeV (per nucleon pair). The modified Tsallis--Pareto-type function (the TP-like function) with average transverse flow velocity is used to describe the contribution of participant or constituent quarks to transverse momentum of considered hadron. The experimental spectra of $π^{\mp}$ and $K^{\mp}$ (or $p$ and $p$ ) are fitted by the convolution of two (or three) TP-like functions due to the fact that two (or three) constituent quarks are regarded as two (or three) energy resources in the formation of considered hadron. From the reasonable fits to the spectra, the thermal freeze-out parameters are extracted, and the pseudo-entropy is newly defined and extracted. Some parameters quickly change in the energy range of less than 7.7 GeV, and slowly change in the energy range of greater than 7.7 GeV, indicating the variation of collision mechanism at around 7.7 GeV.
↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2022)·8 citations
11
A Bayesian analysis of the properties of hybrid stars with the NJL model
Antoine Pfaff🇫🇷 · Hubert Hansen🇫🇷 · Francesca Gulminelli🇫🇷
We implement a Bayesian analysis of the properties of non-rotating hybrid stars at equilibrium with quark matter cores, as described by the SU(3) Nambu--Jona-Lasinio (NJL) model. The hadronic phase is described by a unified metamodeling approach, with a prior parameter space covering the present uncertainties on nuclear matter properties with nucleonic degrees of freedom. The parameter space of the NJL model includes vector-isoscalar and vector-isovector couplings and, additionally, an effective bag constant for the quark pressure is introduced as a free parameter. The phase transition is assumed to be first order with charge neutral phases, following the Maxwell construction. Our Bayesian framework includes filters on the experimental and theoretical low-density nuclear physics knowledge (atomic masses, ab initio calculations of the EoS) and high density constraints from astrophysical observations (maximum mass of J0348+0432, binary tidal deformability of the GW170817 event). We find that microscopic vector interactions play an important role in quark matter in order to stiffen the equation of state sufficiently to reach high star masses, in agreement with previous studies. Even within a very large prior for both the hadronic phase and the quark phase and the important freedom brought by the effective bag constant, our posterior quark cores tend to be relatively small and only appear in very heavy stars ( $M ≳ 2 M_{⊙}$ ). Coincidentally, the inclusion of the nucleon-quark transition (deconfinement transition) only weakly affects the radii of compact stars, foreshadowing a very low observability of a possible phase transition using x-ray radii measurements.
↳ astro-ph.HEhep-phnucl-thPRC(2022)·26 citations
12
Proposed Lunar Measurements of $r$ -Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu
Xilu Wang🇨🇳 · Adam M. Clark🇺🇸 · John Ellis🇬🇧 · Adrienne F. Ertel🇺🇸 · Brian D. Fields🇺🇸 · Brian J. Fry🇺🇸 · Zhenghai Liu🇺🇸 · Jesse A. Miller🇺🇸 · Rebecca Surman🇺🇸
244Pu has recently been discovered in deep-sea deposits spanning the past 10 Myr, a period that includes two 60Fe pulses from nearby supernovae. 244Pu is among the heaviest $r$ -process products, and we consider whether it was created in the supernovae, which is disfavored by nucleosynthesis simulations, or in an earlier kilonova event that seeded 244Pu in the nearby interstellar medium that was subsequently swept up by the supernova debris. We discuss how these possibilities can be probed by measuring 244Pu and other $r$ -process radioisotopes such as 129I and 182Hf, both in lunar regolith samples returned to Earth by missions such as Chang'e and Artemis, and in deep-sea deposits.
↳ astro-ph.HEhep-phnucl-exnucl-th+1Astrophysics(2023)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE

Concerning pion parton distributions

Alpha-alpha scattering in the Multiverse

Thermal freeze-out parameters and pseudo-entropy from charged hadron spectra in high energy collisions

A Bayesian analysis of the properties of hybrid stars with the NJL model

Proposed Lunar Measurements of r-Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu

Affiliations

Proposed Lunar Measurements of $r$ -Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu