Nucleon Resonance Electroexcitation Amplitudes and Emergent Hadron Mass

Particles

article

Daniel S. Carman¹  Ralf W. Gothe²  Victor I. Mokeev¹  Craig D. Roberts³ 

[1] Jefferson Laboratory;Department of Physics and Astronomy, University of South Carolina;School of Physics, Nanjing University;Institute for Nonperturbative Physics, Nanjing University

关键词: exclusive meson photo- and electroproduction;    exclusive reactions with the CLAS and CLAS12 detectors;    nucleon resonance photo- and electroexcitation amplitudes;    nucleon resonance spectrum and structure;    emergence of hadron mass;    continuum Schwinger function methods;    hadron structure and interactions;   

DOI  :  10.3390/particles6010023

学科分类：社会科学、人文和艺术（综合）

来源: mdpi

【 摘 要 】

Understanding the strong interaction dynamics that govern the emergence of hadron mass (EHM) represents a challenging open problem in the Standard Model. In this paper we describe new opportunities for gaining insight into EHM from results on nucleon resonance (N *) electroexcitation amplitudes (i.e.,γ vpN *electrocouplings) in the mass range up to 1.8 GeV for virtual photon four-momentum squared (i.e., photon virtualities Q 2) up to 7.5 GeV 2 available from exclusive meson electroproduction data acquired during the 6-GeV era of experiments at Jefferson Laboratory (JLab). These results, combined with achievements in the use of continuum Schwinger function methods (CSMs), offer new opportunities for charting the momentum dependence of the dressed quark mass from results on the Q 2-evolution of theγ vpN *electrocouplings. This mass function is one of the three pillars of EHM and its behavior expresses influences of the other two, viz. the running gluon mass and momentum-dependent effective charge. A successful description of the Δ( 1232 )3 /2 +and N( 1440 )1 /2 +electrocouplings has been achieved using CSMs with, in both cases, common momentum-dependent mass functions for the dressed quarks, for the gluons, and the same momentum-dependent strong coupling. The properties of these functions have been inferred from nonperturbative studies of QCD and confirmed, e.g., in the description of nucleon and pion elastic electromagnetic form factors. Parameter-free CSM predictions for the electrocouplings of the Δ( 1600 )3 /2 +became available in 2019. The experimental results obtained in the first half of 2022 have confirmed the CSM predictions. We also discuss prospects for these studies during the 12-GeV era at JLab using the CLAS12 detector, with experiments that are currently in progress, and canvass the physics motivation for continued studies in this area with a possible increase of the JLab electron beam energy up to 22 GeV. Such an upgrade would finally enable mapping of the dressed quark mass over the full range of distances (i.e., quark momenta) where the dominant part of hadron mass and N * structure emerge in the transition from the strongly coupled to perturbative QCD regimes.

【 授权许可】

CC BY