N->Delta Quadrupole Transition in the Constituent Quark Model

TL;DR

This paper investigates the electromagnetic N-->Delta quadrupole transition to understand proton deformation, highlighting the importance of exchange currents in explaining experimental E2 strength beyond simple quark model predictions.

Contribution

It demonstrates the dominance of exchange currents in the N-->Delta quadrupole transition, providing a physical mechanism for the observed E2 strength that exceeds simple quark model predictions.

Findings

Exchange currents dominate the N-->Delta quadrupole transition

Experimental E2 strength is about 10 times larger than simple model predictions

Identifies the physical mechanism behind the observed E2 strength

Abstract

Information on the intrinsic deformation of the proton can be obtained by studying the electromagnetic p-->Delta+ quadrupole transition. Recent experiments have shown that the electric quadrupole (E2) strength in gamma p --> Delta+ is about 10 times larger than predicted by the simple quark model using only one-body currents. Our analysis provides evidence for the dominance of exchange currents in the N-->Delta quadrupole transition and identifies the physical mechanism leading to the observed E2 strength.