last update : 01-15-07
This page is a summary of the research I did for my Phd.
Virtual
Compton Scattering (VCS) of
the
proton
below pion threshold :
The scattering of a photon off a proton allows the
measurement
of the rigidity of the internal structure of the nucleon. It is a
fundamental
process as the shape of the proton (as measured with the nucleon form
factors)
is modified under the influence of the scattered photon. Below pion
production
threshold (but arbitrary squared quadri-momentum transfer of the
virtual
photon), the measured observables are the Generalized Polarizabilities
(GP). They generalize the concept of electric and magnetic
polarizabilities
measured in Real Compton Scattering. Between 1995 and 1998 we have
measured
the absolute unpolarized cross-sections for the photon
electro-production
off the Proton with the three-Spectrometer-Setup at MAMI
(Mainz, Germany) at a momentum transfer of 0.33 GeV 2
/c 2
and a virtual photon polarization of 0.62. We extracted two
combinations
of the generalized polarizabilities and compared them to theoretical
predictions
of the non perturbative structure of the nucleon. Our experiment at
Mainz
was the first precise measurement of the photon electro production to
be
carried on, thanks to the advance of the CW beam delivery technology.
Since
that time, similar experiments have been performed at JLab/Hall A and
MIT/Bates.
The advance of the theoretical formalism allows also to measure the GP
in the Delta region where the effect is larger.
- PRL 85, 708 (2000) : "The First determination of generalized polarizabilities of the proton by Virtual Compton Scattering experiment ", J. Roche at al.
- My thesis write-up (in French, careful it is pretty long)
- This research topic was my PhD thesis subject. For this project I worked at the SPhN/CEA/Saclay under the direction of N. D'Hose while being a student registered at the Université B. Pascal (France) .