Nuclear Theory·nucl-th

Monday·November 8, 2021

9 papers—4 primary·5 cross-listed

01
The Gluon Exchange Model in proton-nucleus collisions
Marek Jeżabek🇵🇱 · Andrzej Rybicki🇵🇱
We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton-nucleus reactions involving N>1 proton-nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea-sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number of proton-nucleon collisions in the nucleus. As such, the nuclear stopping power appears to be governed by the emergence of new color configurations as a function of N rather than by the energy loss of the original valence diquark. The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, and a set of predictions for the N-dependence of the baryon stopping process, are included in the letter.
nucl-thhep-phActa Phys.Polon.B(2022)·1 citation
02
Nuclear effects on the $ρ$ meson produced in the inclusive photonuclear reaction
Swapan Das🇮🇳
The hadronic properties of the $ρ$ meson produced in the inclusive photonuclear reaction have been investigated. The elementary reaction occurring in the nucleus is assumed as $γ N \to ρ^{0} N$ . The $ρ$ meson, while propagating through the nucleus, interacts with the nuclear particles, and therefore, the properties of the $ρ$ meson can be modified because of this interaction. Being a short-lived particle, the $ρ$ meson decays to various elementary particles, such as, $e^{+} e^{-}$ , $π^{+} π^{-}$ , .... etc. The $e^{+} e^{-}$ invariant mass, i.e., the $ρ$ meson mass, distribution spectra have been calculated to extract the information about the parameters, viz., mass and width, of the $ρ$ meson in the nucleus. The calculated results have been compared with the data reported from Jefferson Laboratory.
nucl-thPRC(2021)·3 citations
03
Multiple $S O (5)$ isovector pairing and seniority $S p (2Ω)$ multi- $j$ algebras with isospin
V.K.B. Kota · R. Sahu
With nucleons occupying several shell model $j$ orbits, the isovector pair creation operator $A_{μ}^{1}$ (creates a two particle state with angular momentum $J = 0$ and isospin $T = 1$ ) is no longer unique. Choosing it to be a sum of single- $j$ isovector pair creation operators each with a phase, there will be multiple pair $S O (5)$ algebras with isospin; with $r$ number of $j$ orbits, there will be $2^{r - 1}$ $S O (5)$ algebras each with a corresponding complementary $S p (2Ω)$ algebra [ $2Ω = \sum_{j} (2 j + 1)$ ] that gives seniority and reduced isospin quantum numbers. Three applications of multiple $S O (5)$ algebras are presented demonstrating the usefulness of considering $S O (5)$ pairing algebras with general sign factors.
nucl-thBulg.J.Phys.(2021)·1 citation
04
Pauli Blocking for a Relativistic Fermi Gas in Quasielastic Lepton Nucleus Scattering
Arie Bodek🇺🇸
The expressions for the overall effect of Pauli blocking in quasielastic (QE) lepton scattering from nuclear targets within the framework of the Relativistic Fermi Gas (RFG) given in several publications are incorrect. For example, the expressions published by Bell and Llewelyn Smith in 1972 are incorrect (probably a typographical error). The expressions for Pauli blocking presented in several subsequent publications including the paper of C.H. Llewelyn Smith in 1972 and the paper of Paschos and Yu in 2002 have the same error. Another example is a 1992 paper by Singh and Oset which has a different (probably also a typographical) error. Other papers such as the papers of Tsai in 1974 and Bosted and Mamyan in 2012 use the correct expressions. In this short preprint we review the geometrical derivation of the overall reduction of the QE cross sections due to Pauli blocking for electron and neutrino scattering for targets with equal numbers of neutrons and protons and for targets with unequal numbers of neutrons and protons and derive the correct expressions. However, we note that the effects of Pauli blocking within the framework of the RFG model are much larger than in other more realistic models of QE scattering such as $ψ^{'}$ superscaling or a spectral function approach.
nucl-thhep-ph11 citations
05
Confinement in Two-Dimensional QCD and the Infinitely Long Pion
Colin M. Weller🇺🇸 · Gerald A. Miller🇺🇸
Three current models of QCD in (1+1) dimensions are examined and extended in light-front coordinates. A pion of high momentum is found to have an infinite extent along its direction of motion.
↳ hep-phnucl-thPRD(2022)·23 citations
06
Collective effects in neutrino scattering on solid and liquid targets
Georgy Donchenko🇷🇺 · Konstantin Kouzakov🇷🇺 · Alexander Studenikin🇷🇺
Neutrino scattering on liquid and solid targets at low energy transfer can serve both as a tool for searching the physics beyond the Standard Model, for example, such as neutrino electromagnetic interactions, and as a test of the Standard Model at low-energy scale. At the same time, the theoretical apparatus for low-energy elastic neutrino scattering on electrons and nuclei bound in liquids and solids must take into account collective effects in the electron and nuclear subsystems of the target. We develop such an apparatus based on the formalism of the dynamic structure factor. A numerical illustration of the role of the collective effects is provided for the case of a superfluid He-4 target.
↳ hep-phnucl-thPoS(2022)·0 citations
07
Building a realistic neutron star from holography
Nicolas Kovensky🇫🇷 · Aaron Poole🇬🇧 · Andreas Schmitt🇬🇧
We employ the recently improved description of dense baryonic matter within the Witten-Sakai-Sugimoto model to construct neutron stars. In contrast to previous holographic approaches, the presence of an isospin asymmetry allows us to implement beta equilibrium and electric charge neutrality. As a consequence, we are able to model the crust of the star within the same formalism and compute the location of the crust-core transition dynamically. After showing that a simple pointlike approximation for the baryons fails to satisfy astrophysical constraints, we demonstrate that our improved description does account for neutron stars that meet the current experimental constraints for mass, radius, and tidal deformability. However, we also point out tensions in the parameter fit and large- $N_{c}$ artifacts and discuss how to potentially resolve them in the future.
↳ hep-phastro-ph.HEhep-thnucl-thPRD(2022)·64 citations
08
Transverse momentum broadening in real-time lattice simulations of the glasma
Andreas Ipp🇦🇹 · David I. Müller🇦🇹 · Daniel Schuh🇦🇹
The study of jets in heavy-ion collisions provides important information about the interaction of partons with the medium that they traverse. The seeds of jets are highly energetic partons, which are produced from hard scatterings during the collision event. As such, they are affected by all different stages of the medium's time evolution, including the glasma, which is the pre-equilibrium precursor state of the quark-gluon plasma. Here we report on our numerical lattice simulations of partons traversing the boost-invariant, non-perturbative glasma as created at the early stages of collisions at RHIC and LHC. We find that partons quickly accumulate transverse momentum up to the saturation momentum during the glasma stage. Furthermore, we observe an interesting anisotropy in transverse momentum broadening of partons with larger broadening in the rapidity than in the azimuthal direction. Its origin can be related to correlations among the longitudinal color-electric and color-magnetic flux tubes in the initial state of the glasma. We compare these observations to the semi-analytic results obtained by a weak-field approximation, where we also find such an anisotropy in a parton's transverse momentum broadening.
↳ hep-phhep-latnucl-thPoS(2022)·0 citations
09
Dynamics of the $O (4)$ critical point in QCD
Adrien Florio🇺🇸 · Eduardo Grossi🇺🇸 · Alexander Soloviev🇺🇸 · Derek Teaney🇺🇸
We perform a real-time simulation of the $O (4)$ critical point of QCD, which lies in the dynamic universality class of Model G. The axial charge and the order parameter $ϕ_{a} = (σ, π)$ exhibit a rich dynamical interplay, which reflects the qualitative differences in the hydrodynamic effective theories above and below $T_{c}$ . From the axial charge correlators on the critical line we extract a dynamical critical exponent of $ζ = 1.47 \pm 0.01 (stat)$ , which is compatible with the theoretical expectation of $ζ = d /2$ (with $d = 3$ ) when systematic errors are taken into account. At low temperatures, we quantitatively match the $O (4)$ simulations to the superfluid effective theory of soft pions.
↳ hep-lathep-phhep-thnucl-thPRD(2022)·50 citations

Affiliations

first authorsco-authorsvia INSPIRE