A measurement of the differential cross section for the reaction $\gamma n \to \pi^{-} p$ from deuterium

TL;DR

This study measures the differential cross section for the gamma neutron to pion minus proton reaction using CLAS at Jefferson Lab, revealing a broad enhancement around 2.2 GeV and analyzing its angular dependence.

Contribution

First measurement of the differential cross section for gamma n to pi- p from deuterium in this energy and angular range, confirming and extending previous observations.

Findings

Confirmed a broad enhancement at 2.2 GeV in scaled cross section.

Analyzed angular dependence of the enhancement from 70° to 105°.

Provided new data on gamma n to pi- p reaction at high energies.

Abstract

We report a measurement of the differential cross section for the $\gamma n \to \pi^- p$ process from the CLAS detector at Jefferson Lab in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles ($\theta_{c.m.}$) between 50$^\circ$ and 115$^\circ$. We confirm a previous indication of a broad enhancement around a c.m. energy ($\sqrt{s}$) of 2.2 GeV at $\theta_{c.m.}=90^\circ$ in the scaled differential cross section, $s^7 {\frac{d\sigma}{dt}}$. Our data show the angular dependence of this enhancement as the scaling region is approached in the kinematic region from 70$^\circ$ to 105$^\circ$.