[Poster title]

1
Focal Plane Polarimeter
Proton Form Factor
About This Experiment

• Non Point-like Particle

• Low Q2 region (0.30.7 (GeV/c)2)
• High precision (0.5)
• Measure the polarization of the recoil proton

1933 Stern measured Proton magnetic moment
Not that simple

• How are the charge/current distributed
• inside Proton?

A powerful tool electron elastic scattering
1.192GeV
e
Polarized measurement
Recoil Polarization Technique
Leading order of pQED (single photon exchange)
Preliminary Analysis
Unpolarized
Rosenbluth Separation
Experimental Advantages

• Only one measurement is necessary for each Q2
• Much better precision than a cross section
  measurement

What we know
Sachs Form Factors
Dipole form factor
GE related to electric part of interaction GM
related to magnetic part of interaction
Difficulties for Rosenbluth
Exponential charge and magntization distribution
E08-007 statistical uncertainties and world data
at low Q2
Large Q2 not sensitive to GEP Low Q2 not
sensitive to GMP
Rosenbluth and Polarization methods do NOT agree
at high Q2 2g exchange?