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<font color="#000099"><b><font color="#3333ff">Physics Seminar<br>
Wednesday, Apr. 27, 2011<br>
4:00PM<br>
Cebaf Center AUD.<br>
<font color="#3333ff">Cookies & Coffee at 3:45PM<br>
<font color="#cc0000"><br>
</font></font></font></b></font><font color="#cc0000"><big><b>"First
Results from PREX"
</b></big><b><br>
<br>
</b></font><b><big><font color="#cc0000">Robert Michaels
<br>
Jefferson Lab</font>
</big></b><br>
<br>
The Lead Parity Experiment PREX ran in the Spring of 2010 in Hall A and
the results will be presented for the first time. The experiment
measures the parity-violating asymmetry in the elastic scattering of
polarized electrons from a lead nucleus at an energy of 1.06 GeV and a
scattering angle of 5 degrees. The Z0 boson that mediates the weak
interaction couples mainly to neutrons and provides a clean measurement
of the RMS radius of the neutron distribution in the nucleus. This
measurement is a fundamental test of nuclear models and can clearly
establish whether a neutron skin exists in heavy nuclei. An accurate
measurement impacts neutron star structure, heavy ion collisions, and
atomic parity violation measurements. The experiment involves all
aspects of CEBAF, from the polarized source to the detector, and
capitalizes on CEBAF's unique strengths for carrying out high-precision
parity experiments. In addition to the data, several technical
challenges will be described, as well as prospects for future
measurements from lead and other nuclei at Jefferson Lab.
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