[Jlab-seminars] HALL D SEMINAR

[Luci Collins]

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* *"Proton Form Factor Measurements at JLab with Polarization Method: 
Detectors, Analyses, Results and Theoretical Interpretation"

 

*Lubomir Pentchev**
**The College of William and Mary***

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*_ABSTRACT_*

 

*          *The discrepancy between the Rosenbluth and Polarization 
results for the proton form factor ratio has not been resolved yet, 
almost 10 years after it was discovered in the first GEp experiment in 
Hall A at JLab. Significant experimental and theoretical efforts have 
been made to reconcile the results and also to extend the form factor 
measurements up to highest possible Q^2 using the polarization method.

 

A new, 1744 channel electromagnetic calorimeter, BigCal has been built 
for the recent Hall C experiments: GEp-2gamma and GEp-3. Details of the 
calorimeter performance will be presented.  Critical issues in the 
analyses will be discussed and preliminary results from the two 
experiments will be presented. GEp-2gamma was the first experiment to 
investigate at percent level effects beyond Born approximation in the 
proton form factor ratio measurements. The GEp-2gamma results will be 
discussed and a brief review of the two-photon exchange calculations 
will be given. GEp-3 measured the form factor ratio up to Q^2 of 8.5 
GeV2. The 12 GeV upgrade will make it possible to target Q^2 values of 
15 GeV^2 . To achieve the needed high detector acceptance at very high 
luminosities, an experiment, that will use GEM technology for tracking 
and calorimetry for triggering, will be described.

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*Friday, October 23, 2009*

*10:00AM*

*CEBAF Center F113***



 
 

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