Nuclear Theory·nucl-th

Monday·June 19, 2023

7 papers—3 primary·4 cross-listed

01
The paradox of coherent photoproduction in incoherent interactions
Spencer R. Klein🇺🇸
The Good-Walker (GW) paradigm relates coherent and incoherent exclusive reactions to the average target configuration and its nucleonic and partonic fluctuations. In it, coherent photoproduction occurs when the target remains in the ground state, while, in incoherent photoproduction, the target breaks up. However, the GW paradigm fails to explain the observation of coherent vector meson photoproduction accompanied by nuclear breakup in ultra-peripheral collisions (UPCs) , and in peripheral relativistic heavy-ion collisions. In the latter, hundreds of particles can be created. This writeup will explore this paradox, and also present an alternate, semi-classical approach toward coherent production: adding the amplitudes with an appropriate propagator. The semi-classical approach explains the transverse momentum dependence of exclusive vector meson production in UPCs, but does not address the target final state. I will address these two approaches, and suggest possible future work to resolve the paradox \cite{Klein:2023zlf}.
nucl-thhep-ph1 citation
02
Open charm phenomenology with a multi-stage approach to relativistic heavy-ion collisions
Mayank Singh🇺🇸 · Manu Kurian🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
We study open charm flavor observables in Pb+Pb collision at $s_{N N} = 2.76$ TeV within the MARTINI framework. The space-time expansion of the quark-gluon plasma is described using the hydrodynamical approach-MUSIC with IP-Glasma initial conditions. The model parameters, including the viscous coefficients, were obtained from a recent Bayesian model-to-data comparison. We evolve heavy quarks in this background using Langevin dynamics while incorporating their collisional and radiative processes in the medium. The sensitivity of charm observables to the IP-Glasma initial state, bulk evolution, and centrality of the collision is studied. We find that the elliptic flow of open charm flavor has a strong dependence on the fluctuating initial conditions in addition to the strength of the interaction of heavy quarks with the medium constituents. Within this framework, the nuclear suppression factor and elliptic flow of D-mesons act as efficient probes to study the initial stages of heavy-ion collisions, transport coefficients associated with QGP medium as well as heavy quark interactions.
nucl-thhep-phPRC(2023)·28 citations
03
Early-times Yang-Mills dynamics and the characterization of strongly interacting matter with statistical learning
Matthew R. Heffernan🇨🇦 · Charles Gale🇨🇦 · Sangyong Jeon🇨🇦 · Jean-François Paquet🇺🇸
In ultrarelativistic heavy-ion collisions, a plasma of deconfined quarks and gluons is formed within $1$ fm/c of the nuclei's impact. The complex dynamics of the collision before $\approx 1$ fm/c is often described with parametric models, which affect the predictivity of calculations. In this work, we perform a systematic analysis of LHC measurements from Pb-Pb collisions, by combining an \emph{ab-initio} model of the early stage of the collisions with a hydrodynamic model of the plasma. We obtain state-of-the-art constraints on the shear and bulk viscosity of quark-gluon plasma. We mitigate the additional cost of the ab-initio initial conditions by combining Bayesian model averaging with transfer learning, allowing us to account for important theoretical uncertainties in the hydrodynamics-to-hadron transition. We show that, despite the apparent strong constraints on the shear viscosity, metrics that balance the model's predictivity with its degree of agreement with data do not prefer a temperature-dependent specific shear viscosity over a constant value. We validate the model by comparing with discriminating observables not used in the calibration, finding excellent agreement.
nucl-thhep-phnucl-exPRL(2024)·41 citations
04
Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab
A. Accardi🇺🇸 · P. Achenbach🇺🇸 · D. Adhikari🇺🇸 · A. Afanasev🇺🇸 · C.S. Akondi🇺🇸 · N. Akopov🇦🇲 · M. Albaladejo🇪🇸 · H. Albataineh🇺🇸 · M. Albrecht🇺🇸 · B. Almeida-Zamora🇲🇽 · M. Amaryan🇺🇸 · D. Androić🇭🇷 and 432 other authors
This document presents the initial scientific case for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) to 22 GeV. It is the result of a community effort, incorporating insights from a series of workshops conducted between March 2022 and April 2023. With a track record of over 25 years in delivering the world's most intense and precise multi-GeV electron beams, CEBAF's potential for a higher energy upgrade presents a unique opportunity for an innovative nuclear physics program, which seamlessly integrates a rich historical background with a promising future. The proposed physics program encompass a diverse range of investigations centered around the nonperturbative dynamics inherent in hadron structure and the exploration of strongly interacting systems. It builds upon the exceptional capabilities of CEBAF in high-luminosity operations, the availability of existing or planned Hall equipment, and recent advancements in accelerator technology. The proposed program cover various scientific topics, including Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic highlights the key measurements achievable at a 22 GeV CEBAF accelerator. Furthermore, this document outlines the significant physics outcomes and unique aspects of these programs that distinguish them from other existing or planned facilities. In summary, this document provides an exciting rationale for the energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific potential that lies within reach, and the remarkable opportunities it offers for advancing our understanding of hadron physics and related fundamental phenomena.
↳ nucl-exhep-exhep-phnucl-thEPJA(2024)·223 citations
05
Transverse momentum dependent factorization for SIDIS at next-to-leading power
Simone Rodini🇫🇷 · Alexey Vladimirov🇪🇸
The semi-inclusive deep-inelastic scattering (SIDIS) is the golden process for investigating the nucleon's transverse momentum-dependent (TMD) structure. We present the complete expression for SIDIS structure functions in the TMD factorization formalism at the next-to-leading power. All perturbative elements of the factorization theorem -- coefficient functions and evolution kernels -- are presented at one-loop accuracy. We found several differences with earlier derivations, which are due to accounting for nontrivial kinematics of the quark-gluon interference terms. As a side result, we present the definition and evolution of twist-three TMD fragmentation functions, including the leading-order evolution kernel.
↳ hep-phnucl-thPRD(2024)·30 citations
06
Skin values and matter radii of $^{208}$ Pb and $^{58, 60, 64}$ Ni based on reaction cross section of $^{3, 4}$ He scattering (published in Results in Physics)
Shingo Tagami · Tomotsugu Wakasa · Masanobu Yahiro
The PREX group reported a new skin value, $r_{skin}^{208} (PREX2) = 0.283 \pm 0.071 fm$ . Using the chiral (Kyushu) $g$ -matrix folding model with the proton and neutron densities determined with D1S+GHFB+AMP, we determined neutron skin thickness $r_{skin}^{208} (exp)$ from reaction cross sections $σ_{R} (exp)$ of p+ $^{208}$ Pb scattering. The method also yielded $r_{skin}^{208} (exp)$ from $σ_{R} (exp)$ of $^{4}$ He+ $^{208}$ Pb scattering. We accumulated the 206 EoSs and determined a sloop parameter from the 206 EoSs. The value yields $r_{skin}^{208} = 0.102 \sim 0.354 fm$ . As the first aim, we first determine $r_{skin}^{208} (exp)$ from $σ_{R} (exp)$ of $^{3}$ He scattering on $^{208}$ Pb target and take the weighted mean and its error for $r_{skin}^{208} (PREX2)$ , three skin values of p+ $^{208}$ Pb, $^{3, 4}$ He+ $^{208}$ Pb scattering and the $r_{skin}^{208}$ based on the 206 EoSs. As the second aim, we determine matter radii $r_{m} (exp)$ of $^{58, 60, 64}$ Ni from $σ_{R} (exp)$ of $^{3, 4}$ He scattering on $^{58, 60, 64}$ Ni targets. Our result is $r_{skin}^{208} (exp) = 0.512 \pm 0.268 fm$ for $^{3}$ He+ $^{208}$ Pb scattering. Our conclusion is $r_{skin}^{208} = 0.285 \pm 0.030 fm$ . It is determined from the 5 skin values mentioned above.
↳ nucl-exnucl-th1 citation
07
Towards a Stability Analysis of Inhomogeneous Phases in QCD
Theo F. Motta🇩🇪 · Julian Bernhardt🇩🇪 · Michael Buballa🇩🇪 · Christian S. Fischer🇩🇪
The possible occurrence of crystalline or inhomogeneous phases in the QCD phase diagram at large chemical potential has been under investigation for over thirty years. Such phases are present in models of QCD such as the Gross-Neveu model in 1+1 dimensions, Nambu-Jona-Lasinio (NJL) and quark meson models. Yet, no unambiguous confirmation exists from actual QCD. In this work, we propose a new approach for a stability analysis that is based on the two-particle irreducible effective action and compatible with full QCD calculations within the framework of functional methods. As a first test, we reproduce a known NJL model result within this framework. We then discuss the additional difficulties which arise in QCD due to the non-locality of the quark self-energy and suggest a method to overcome them. As a proof of principle and as an illustration of the analysis, we consider the Wigner-Weyl solution of the quark Dyson-Schwinger equation (DSE) within a simple truncation of QCD in the chiral limit and analyse its stability against homogeneous chiral-symmetry breaking fluctuations. For temperatures above and below the tricritical point we find that the boundary of the instability region coincides well with the second-order phase boundary or the left spinodal, respectively, obtained from the direct solutions of the DSEs. Finally, we outline how this method can be generalized to study inhomogeneous fluctuations.
↳ hep-phnucl-thPRD(2023)·31 citations

Affiliations

first authorsco-authorsvia INSPIRE

The paradox of coherent photoproduction in incoherent interactions

Open charm phenomenology with a multi-stage approach to relativistic heavy-ion collisions

Early-times Yang-Mills dynamics and the characterization of strongly interacting matter with statistical learning

Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab

Transverse momentum dependent factorization for SIDIS at next-to-leading power

Skin values and matter radii of 208Pb and 58,60,64Ni based on reaction cross section of 3,4He scattering (published in Results in Physics)

Towards a Stability Analysis of Inhomogeneous Phases in QCD

Affiliations

Skin values and matter radii of $^{208}$ Pb and $^{58, 60, 64}$ Ni based on reaction cross section of $^{3, 4}$ He scattering (published in Results in Physics)