<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body bgcolor="#ffffff" text="#000000">
<font color="#000099"><b><font color="#3333ff">Seminar <br>
Monday, Oct. 26, 2009<br>
10:00 AM<br>
CEBAF Center F113<br>
<br>
Sam Boblit<br>
BNL<br>
<br>
</font></b></font>
<pre><font color="#cc0000">
<b>"Recent results of double polarization pion photoproduction
measurements with frozen-spin HDice from the LEGS facility at BNL."</b></font>
The last round of experiments at the Laser-Electron-Gamma-Source facility at
Brookhaven produced tagged polarized photon beams up to 0.4 GeV and utilized
frozen-Spin HDice targets to measure spin-dependent pion production cross
sections. A quasi-4pi spectrometer was used, first in a calorimeter mode
optimized for neutrals and then incorporating a Time-Projection Chamber and
solenoid to provide pi +/- charge separation. Inclusive results for the
photo-production of charged and neutral pions on the proton have provided
new information on the convergence of the Gerasimov-Drell-Hearn-Hosoda-
Yamamoto (GDH) sum rule. Recent results from Mainz and Bonn exceeded the GDH
prediction for the proton by 22 microbarns. LEGS pi0 data reveal a different
angular dependence from that assumed in Mainz analysis and integrate to a
value 18 microbarns lower, indicating a rapid convergence. Inclusive results
on Deuterium are lower than existing state of the art calculations for the
GDH integrand in Deuterium. Preliminary exclusive results for D(gamma,pi0n)p
allow a separation of coherent and incoherent pi0 production on D and shed
some light on these differences. Restrictive kinematic requirements on these
exclusive pi0 n data will also provide the first spin-data in pi0 production
from an approximately free neutron.</pre>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<font color="#000099"><br>
<b><br>
</b></font><br>
</body>
</html>