Proton form factors: Measurement of the proton form factors ratio up to Q(2) = 5.6 GEV(2) by recoil polarimetry

• Main Author: Gayou, Olivier
• Format: Others
• Language: English
• Published: W&M ScholarWorks 2002
• Online Access: https://scholarworks.wm.edu/etd/1539623396; https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=3187&context=etd

In this thesis, we present the results of the experiment E99-007, which measured the ratio of the electric to magnetic form factors of the proton to the four momentum transfer square Q2 = 5.6 GeV2, by recoil polarimetry. Data were taken in 2000 at the Thomas Jefferson National Accelerator Facility in Virginia, USA. A 4.6 GeV polarized electron beam was scattered off a cryogenic hydrogen target. The polarization of the recoil proton was measured in the Focal Plane Polarimeter, located after one of the two High Resolution Spectrometers in the hall. The ratio of the transverse to longitudinal components of the recoil proton polarization is proportional to the ratio of the form factors. Elastic events were selected by detecting the scattered electron in a large acceptance lead-glass calorimeter.;The main result of this experiment is the linear decrease of the form factor ratio with increasing Q2, corresponding to different spatial distributions of the electric charge and the magnetization. Numerous theoretical calculations show that relativistic effects, such as mixing of spin states due to Lorentz boosts, are important to account for the observed data in this critical intermediate kinematic region.