Antibaryon Photoproduction Using CLAS at Jefferson Lab

Antibaryon production has been investigated since the advent of nuclear physics, largely motivated by the potential for baryon-antibaryon bound states. Due to the recent availability of high statistics experiments there has been a renewed interest in how antibaryons are created in photoproduction. The g12 (E04-005) experiment conducted at Thomas Jefferson National Accelerator Facility used the CEBAF Large Acceptance Spectrometer to provide the world’s largest dataset for baryon-antibaryon photoproduction on a liquid hydrogen tar- get. The focus of this work is to investigate the photoproduction mechanism of γp → ppp¯ through detailed differential cross section measurements from 3.95 to 5.45 GeV. These first time results as well as the resulting total cross section measurement are reported. In particular the energy dependence (σ(Eγ)) and the angular dependence (dσ/dcos(&thetas; CMp)) have interesting features that have never been seen before. On the other hand, the mass distributions (dσ/ dM(pp) and dσ/dM (pp¯) do not show evidence for previously reported narrow resonances. In addition, the first time total cross section mesurement of an antineutron in photoproduction using the reaction γp → ppn¯π– is reported. The significance and implications of these results will be discussed as well