Roper Resonance Structure and Exploration of Emergent Hadron Mass from CLAS Electroproduction Data

TL;DR

This paper investigates the structure of the Roper resonance using CLAS electroproduction data, revealing its complex quark and meson-baryon components, and demonstrates how these studies shed light on the strong interaction dynamics responsible for most of hadron mass.

Contribution

It presents new insights into the Roper resonance structure and its evolution with photon virtuality, linking experimental data with the Continuum Schwinger Method to understand hadron mass generation.

Findings

Roper resonance is a complex interplay of quark core and meson-baryon cloud.

Electroexcitation amplitudes evolve with photon virtuality $Q^2$.

Studies provide insight into the strong interaction dynamics generating hadron mass.

Abstract

The $N(1440)1/2^+$ nucleon resonance, first identified in 1964 by L.D. Roper and collaborators in analyses of $\pi N$ hadroproduction data have continued to provide pivotal insights that serve to advance our understanding of nucleon excited states. In this contribution, we present results from studies of the structure of the Roper resonance based on exclusive $\pi N$ and $\pi^+\pi^-p$ electroproduction data measured with the CLAS detector at Jefferson Lab. These analyses have revealed the Roper resonance as a complex interplay between an inner core of three dressed quarks and an external meson--baryon cloud. Analyses of the CLAS results on the evolution of the Roper resonance electroexcitation amplitudes with photon virtuality $Q^2$, within the framework of the Continuum Schwinger Method, have conclusively demonstrated the capability to gain insight into the strong interaction dynamics responsible for generating more than 98\% of hadron mass. Further extension of such studies to higher $Q^2$--through experiments currently underway with the CLAS12 detector and in the future with a potential CEBAF energy upgrade to 22 GeV--offers the only foreseeable opportunity to explore the full range of distances where the dominant portion of hadron mass and resonance structure emerges.