Deep exclusive $\pi^+$ electroproduction off the proton at CLAS

TL;DR

This study measures the cross sections of exclusive $ m{ extpi}^+$ electroproduction off protons at Jefferson Lab, comparing results with hadronic and partonic models to explore the potential for accessing transversity GPDs.

Contribution

First high-precision measurement of $ m{ extpi}^+$ electroproduction cross sections over a broad kinematic range at Jefferson Lab, comparing data with theoretical models to test their validity.

Findings

Both models describe gross features of the data reasonably well.

Data can potentially access transversity Generalized Parton Distributions.

Statistical accuracy of measurements is a few percent in most bins.

Abstract

The exclusive electroproduction of $\pi^+$ above the resonance region was studied using the $\rm{CEBAF}$ Large Acceptance Spectrometer ($\rm{CLAS}$) at Jefferson Laboratory by scattering a 6 GeV continuous electron beam off a hydrogen target. The large acceptance and good resolution of $\rm{CLAS}$, together with the high luminosity, allowed us to measure the cross section for the $\gamma^* p \to n \pi^+$ process in 140 ($Q^2$, $x_B$, $t$) bins: $0.16<x_B<0.58$, 1.6 GeV$^2<$$Q^2$$<4.5$ GeV$^2$ and 0.1 GeV$^2<$$-t$$<5.3$ GeV$^2$. For most bins, the statistical accuracy is on the order of a few percent. Differential cross sections are compared to two theoretical models, based either on hadronic (Regge phenomenology) or on partonic (handbag diagram) degrees of freedom. Both can describe the gross features of the data reasonably well, but differ strongly in their ingredients. If the handbag approach can be validated in this kinematical region, our data contain the interesting potential to experimentally access transversity Generalized Parton Distributions.