The Search for Exotic Mesons in γp→π[sup +]π[sup +]π[sup −]n with CLAS at Jefferson Lab

Abstract

In addition to ordinary qq̄ pairs, quantum chromodynamics (QCD) permits many other possibilities in meson spectra, such as gluonic hybrids, glueballs, and tetraquarks. Experimental discovery and study of these exotic states provides insight on the nonperturbative regime of QCD. Over the past twenty years, some searches for exotic mesons have met with controversial results, especially those obtained in the three‐pion system. Prior theoretical work indicates that in photoproduction one should find gluonic hybrids at significantly enhanced levels compared to that found in pion production. To that end, the CLAS g12 run was recently completed at Jefferson Lab, using a liquid hydrogen target and tagged photons from a 5.71 GeV electron beam. The CLAS experimental apparatus was modified to maximize forward acceptance for peripheral production of mesons. The resulting data contains the world’s largest 3π photoproduction dataset, with γp→π+π+π−n events numbering in the millions. Early results describing the data quality, kinematics, and dysnamics will be shown.