Electroproduction of the Delta Resonance at High Momentum Transfer

TL;DR

This study investigates the electroproduction of the Delta(1232) resonance at unprecedented high momentum transfers, measuring decay distributions and extracting transition form factors, revealing non-perturbative QCD behavior.

Contribution

It provides the first measurements of exclusive resonance electroproduction at Q^2 = 2.8 and 4.0 GeV^2, and extracts transition form factors and multipole ratios at these high momentum transfers.

Findings

Transition form factor G*_M measured at high Q^2

Resonant multipole ratios remain small

Perturbative QCD not applicable at these Q^2

Abstract

We studied the electroproduction of the Delta(1232) resonance via the reaction p(e,e'p)\pi0 at four-momentum transfers Qsq = 2.8 and 4.0 GeV^2. This is the highest Qsq for which exclusive resonance electroproduction has ever been observed. Decay angular distributions for Delta to p-pi0$ were measured over a wide range of barycentric energies covering the resonance. The $N-\Delta$ transition form factor G*_M and ratios of resonant multipoles E{1+}/M{1+} and S{1+}/M{1+} were extracted from the decay angular distributions. These ratios remain small, indicating that perturbative QCD is not applicable for this reaction at these momentum transfers.