[Jlab-seminars] Physics Seminar Announcement

[Luci Collins]

*Physics Seminar
Friday, April 16, 2009
11:00AM
CEBAF Center AUD.
Cookies & Coffee at 10:45AM

*Simona Malace
University of South Carolina

"The Proton in the Nuclear Medium: JLab Experimental Constraints on the 
Modeling of 4He(e,e'p)3H Reaction"

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.


Upcoming Seminars
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April 23: John Schiffer (ANL)



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