Baryon-antibaryon photoproduction cross sections off the proton

TL;DR

This paper reports the first measurements of baryon-antibaryon photoproduction cross sections off the proton at energies up to 11.6 GeV, revealing angular distributions, cross sections, and model consistency without narrow resonances.

Contribution

It provides new experimental data on hyperon and proton-antiproton photoproduction and introduces a phenomenological model explaining the observed distributions.

Findings

Angular distributions are forward peaked for all pairs.

Cross sections and distributions are measured and match a double t-channel exchange model.

No narrow resonant structures were observed in the reaction channels.

Abstract

The GlueX experiment at Jefferson Lab has observed $p\bar{p}$ and, for the first time, $\Lambda\bar{\Lambda}$ and $p\bar{\Lambda}$ photoproduction from a proton target at photon energies up to 11.6 GeV. The angular distributions are forward peaked for all produced pairs, consistent with Regge-like $t$-channel exchange. Asymmetric wide-angle anti-baryon distributions show the presence of additional processes. In a phenomenological model, we find consistency with a double $t$-channel exchange process where anti-baryons are created only at the middle vertex. The model matches all observed distributions with a small number of free parameters. In the hyperon channels, we observe a clear distinction between photoproduction of the $\Lambda\bar{\Lambda}$ and $p\bar{\Lambda}$ systems but general similarity to the $p\bar{p}$ system. We report both total cross sections and cross sections differential with respect to momentum transfer and the invariant masses of the created particle pairs. No narrow resonant structures were found in these reaction channels. The suppression of $s\bar{s}$ quark pairs relative to $d\bar{d}$ quark pairs is similar to what has been seen in other reactions.