[Clas_hadron] Abstract for April APS meeting

[Diane Schott]

Sorry about the format problem. I will keep the most recent copy in
/site/www/html/Hall-B/secure/clas_hadron/abstracts/2012/APS-April12-dschott.pdf

Here's the latest in latex format:

Over twenty years ago QCD-inspired models of hadronic states suggested the
existence of mesons beyond the Naive Quark Model (NQM), which motivated a
rigorous search for so-called exotic mesons. The lightest of these states
is the $\pi_1(1400)$ decaying to $\eta\pi^-$, this was observed in E852 at
Brookhaven and confirmed in data previously taken for VES at IHEP.
Photoproduction is predicted to favor production of the $J^{PC}=1^{-+}$
state resulting in the increase of the ratio of $\pi_1$ to $a_2$ mesons. A
Partial Wave Analysis was conducted on the reaction $\gamma
p\to\Delta^{++}X\to p\pi^+\pi^-(\eta)$, using the $\Delta^{++}$ to select
the $\pi$ exchange. The analysis has shown the final spectra of the
resonance decaying to $\eta\pi^-$ to be dominated by the quantum state of
$J^{PC}=2^{++}$ corresponding to the presence of the $a_2(1320)$. The
$J^{PC}=1^{-+}$ state, shows no structure in the intensity distribution.
However, the phase difference between the $J^{PC}=1^{-+}$ and
$J^{PC}=2^{++}$ amplitudes show the interference between the two states.
The PWA mass independent fits, along with the mass dependent fits of the
partial wave results, will be shown.