Nuclear Theory·nucl-th

Friday·January 7, 2022

9 papers—4 primary·5 cross-listed

05
Hyperons and $Θ_{s}^{+}$ in Holographic QCD
Yizhuang Liu🇵🇱 · Maciej A. Nowak🇵🇱 · Ismail Zahed🇺🇸
We revisit the holographic description of strange baryons in the context of the Sakai-Sugimoto construction, by considering the strange quark mass as heavy. Hyperons are described by a massive $(K, K^{*})$ multiplet, bound to a light-flavor instanton in bulk, much in the spirit of the Callan-Klebanov construction. The modular Hamiltonian maps onto the Landau problem, a charged particle in a 2-dimensional external magnetic field, induced by the bulk Chern-Simons interaction, plus spin-orbit coupling. The ensuing holographic hyperon spectrum compares fairly with the empirical one. The holographic strange pentaquark baryon $Θ_{s}^{+}$ is shown to be unbound.
↳ hep-phnucl-exnucl-thPRD(2022)·5 citations
06
Status of Lattice QCD Determination of Nucleon Form Factors and their Relevance for the Few-GeV Neutrino Program
Aaron S. Meyer🇺🇸 · André Walker-Loud🇺🇸 · Callum Wilkinson🇺🇸
Calculations of neutrino-nucleus cross sections begin with the neutrino-nucleon interaction, making the latter critically important to flagship neutrino oscillation experiments, despite limited measurements with poor statistics. Alternatively, lattice QCD (LQCD) can be used to determine these interactions from the Standard Model with quantifiable theoretical uncertainties. Recent LQCD results of $g_{A}$ are in excellent agreement with data, and results for the (quasi-)elastic nucleon form factors with full uncertainty budgets are expected within a few years. We review the status of the field and LQCD results for the nucleon axial form factor, $F_{A} (Q^{2})$ , a major source of uncertainty in modeling sub-GeV neutrino-nucleon interactions. Results from different LQCD calculations are consistent, but collectively disagree with existing models, with potential implications for current and future neutrino oscillation experiments. We describe a road map to solidify confidence in the LQCD results and discuss future calculations of more complicated processes, important to few-GeV neutrino oscillation experiments.
↳ hep-lathep-exhep-phnucl-ex+1Ann.Rev.Nucl.Part.Sci.(2022)·81 citations
07
Anomalous enhancement of dilepton production as a precursor of color superconductivity
Toru Nishimura🇯🇵 · Masakiyo Kitazawa🇯🇵 · Teiji Kunihiro🇯🇵
We compute the modification of the photon self-energy due to dynamical diquark fluctuations developed near the critical temperature of the color superconductivity through the Aslamasov-Larkin, Maki-Thompson and density of states terms, which are responsible for the paraconductivity in metals at vanishing energy and momentum. It is shown that the rate has a significant enhancement at low invariant-mass region over a rather wide range of temperature in the normal phase. This enhancement is worth exploration in the relativistic heavy-ion collisions, which may thereby reveal the significance of the diquark fluctuations in dense quark matter.
↳ hep-phnucl-exnucl-thPTEP(2022)·18 citations
08
Analyzing transverse momentum spectra by a new method in high-energy collisions
Li-Li Li🇨🇳 · Fu-Hu Liu🇨🇳 · Muhammad Waqas🇨🇳 · Muhammad Ajaz🇵🇰
We analyzed the transverse momentum spectra of positively and negatively charged pions ( $π^{+}$ and $π^{-}$ ), positively and negatively charged kaons ( $K^{+}$ and $K^{-}$ ), protons and antiprotons ( $p$ and $p ˉ$ ), as well as $ϕ$ produced in mid-(pseudo)rapidity region in central nucleus--nucleus (AA) collisions over a center-of-mass energy range from 2.16 to 2760 GeV per nucleon pair. The transverse momentum of the considered particle is regarded as the joint contribution of two participant partons which obey the modified Tsallis-like transverse momentum distribution and have random azimuths in superposition. The calculation of transverse momentum distribution of particles is performed by the Monte Carlo method and compared with the experimental data measured by international collaborations. The excitation functions of effective temperature and other parameters are obtained in the considered energy range. With the increase of collision energy, the effective temperature parameter increases quickly and then slowly. The boundary appears at around 5 GeV, which means the change of reaction mechanism and/or generated matter.
↳ hep-phhep-exnucl-exnucl-thUniverse(2022)·17 citations
09
How well do we know the gluon polarization in the proton?
Y. Zhou🇨🇳 · N. Sato🇺🇸 · W. Melnitchouk🇺🇸
We perform the first simultaneous global QCD analysis of spin-averaged and spin-dependent parton distribution functions (PDFs), including single jet production data from unpolarized and polarized hadron collisions. We critically assess the impact of SU(3) flavor symmetry and PDF positivity assumptions on the quark and gluon helicity PDFs, and find strong bias from these, particularly on the gluon polarization. The simultaneous analysis allows for the first time extraction of individual helicity-aligned and antialigned PDFs with a consistent treatment of uncertainties.
↳ hep-phhep-exnucl-thPRD(2022)·62 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hyperons and Θs+​ in Holographic QCD

Status of Lattice QCD Determination of Nucleon Form Factors and their Relevance for the Few-GeV Neutrino Program

Anomalous enhancement of dilepton production as a precursor of color superconductivity

Analyzing transverse momentum spectra by a new method in high-energy collisions

How well do we know the gluon polarization in the proton?

Affiliations

Hyperons and $Θ_{s}^{+}$ in Holographic QCD