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<font color="#000099"><b><font color="#3333ff">Physics Seminar<br>
Friday, Feb. 18, 2011<br>
11:00AM<br>
Cebaf Center AUD.<br>
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<b><font color="#990000">Kent Paschke
<br>
University of Virgina
<br>
<br>
"HAPPEX-III and Strangeness Contributions
<br>
to the Nucleon Vector Form-Factors"</font></b>
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Precision measurements of parity violation in electron-nucleus elastic
scattering are sensitive to possible strange quark contributions to the
electric and magnetic form-factors of the nucleon. Such measurements
provide a unique opportunity to illuminate the role of the quark-
antiquark sea in low-energy Quantum Chromodynamics. While published
results have placed a tight upper-bound on strange quark contributions
to the electric form-factor at low Q<sup class="moz-txt-sup">2</sup>,
they have not ruled out possible significant contributions to the
proton magnetic form-factor.
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<br>
The HAPPEX-III collaboration has completed a measurement of
parity-violation in forward angle scattering at Q<sup
class="moz-txt-sup">2</sup> of 0.62 [GeV]<sup class="moz-txt-sup">2</sup>
with much greater precision than had previously been achieved in that
kinematic range. This measurement is an important complement to the
existing world data, and in particular will test a region where
previous results appear to suggest a positive signal. The result of
the HAPPEX-III measurement will be revealed, and implications for the
determination of the strange vector form-factors discussed.<br>
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