Measurement of Compton Scattering at MAMI for the Extraction of the Electric and Magnetic Polarizabilities of the Proton

Abstract

A precise measurement of the differential cross sections dσ/dω and the linearly polarized photon beam asymmetry ς3 for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: αE1=10.99±0.16±0.47±0.17±0.34, βM1=3.14±0.21±0.24±0.20±0.35; in units of 10-4 fm3 where the errors are statistical, systematic, spin polarizability dependent, and model dependent.