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<font color="#000099"><b><font color="#3333ff">Physics Seminar<br>
Friday, April 16, 2009<br>
11:00AM<br>
CEBAF Center AUD.<br>
Cookies & Coffee at 10:45AM<br>
<br>
</font></b></font>Simona Malace
<br>
University of South Carolina
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"The Proton in the Nuclear Medium: JLab Experimental Constraints on the
Modeling of 4He(e,e'p)3H Reaction"
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Whether the nucleon changes its fundamental properties while embedded
in nuclear medium has been a fundamental, long-lasting question in
nuclear physics. Two experiments in Hall A, at Jefferson Lab, E93-049
and E03-104, set out to investigate the properties of nucleons inside
nuclear medium using the quasielastic scattering off 4He via the
polarization transfer technique. The polarization-transfer double
ratio and the induced polarization, P_y, have been extracted in the
reactions 4He(vec e,e' vec p)3H and H(vec e,e' vec p) with great
accuracy. The polarization-transfer double ratio has been modeled by
two competing theoretical predictions: the RDWIA calculation by the
Madrid group which uses medium-modified form factors by the QMC model
and the calculation of Schiavilla et al. which assumes free nucleon
form factors but has different modeling of nuclear conventional
effects, in particular the final-state interactions. The two
calculations, however, give different predictions for the induced
polarization P_y, which is largely insensitive to nuclear medium
modifications of the nucleon structure but fully sensitive to
conventional nuclear medium effects. Thus, whether the two models give
an accurate description of P_y has become the key in the interpretation
of the polarization-transfer double ratio. I will present a summary of
the analysis of the induced polarization P_y and comparisons of our
preliminary results from E03-104 to calculations from Madrid and
Schiavilla.
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Upcoming Seminars
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April 23: John Schiffer (ANL)<br>
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