The Search for Exotic Mesons in gamma p -> pi+pi+pi-n with CLAS at Jefferson Lab

Abstract

The ${\pi }_1(1600)$, a $J^{PC}=1^{-+}$ exotic meson has been observed by experiments using pion beams. Theorists predict that photon beams could produce gluonic hybrid mesons, of which the ${\pi }_1(1600)$ is a candidate, at enhanced levels relative to pion beams. The g12 rungroup at Jefferson Lab's CEBAF Large Acceptance Spectrometer (CLAS) has recently acquired a large photoproduction dataset, using a liquid hydrogen target and tagged photons from a 5.71 GeV electron beam. A partial-wave analysis of 502K $\gamma p\to {\pi }^{+}{\pi }^{+}{\pi }^{-}n$ events selected from the g12 dataset has been performed, and preliminary fit results show strong evidence for well-known states such as the $a_1(1260)$, $a_2(1320)$, and ${\pi }_2(1670)$. However, we observe no evidence for the production of the ${\pi }_1(1600)$ in either the partial-wave intensities or the relative complex phase between the $1^{-+}$ and the $2^{-+}$ (corresponding to the ${\pi }_2$) partial waves.

arXiv commentProceedings from the XIV International Conference on Hadron Spectroscopy (HADRON2011) 5 pages, 3 figures