Corrections to the Electron Compton Scattering Cross Section

Corrections to the Electron Compton Scattering Cross Section Liping Gan University of North Carolina Wilmington Dec 16, 2006

Single Compton Scattering Cross section is first calculated by Klein and Nishina in 1929:

Virtual-Photon Radiative Correction • Calculated by Brown and Feynman in 1952: • Contribution to the measurement result is independent of experimental setup.

Double Compton scattering with one soft photon Contributions to the measurement is independent of the experimental setup and analysis procedures.

Double Compton scattering with one hard photon Contributions to the measurement depend on the experimental setup and analysis procedures. There are two cases in our experiment: • Case (a), Unsymmetrical photon pair with an undetected photon’s energy within the Compton selection cuts. • Case (b), Both scattering photons have relatively large energies, however, they hit on the HYCAL with a small opening angle which are misidentified as a single cluster by HYCAL.

Calculation based on the Work of Mykhailo Konchatnyi • Theory inputs based on work of Brown and Feynman (<1%) • Estimated numerical error is at <1%.

Corrections to differential cross sections

Corrections to integrated forward (0. 325 o<θ<3. 60 o) cross sections Slope is about 1% per σ !

How to compare with measurements? • Calculate soft-virtual cross section and hard double Compton cross section separately. • Calculate hard double Compton cross section by Monte Carlo in order to implement all Compton cuts. • Experimental analysis should include corrections to the differential cross section (soft-virtual part) to calculate acceptance. • Suggest to use θ to define fiducial acceptance of Compton in order to improve the precision of theoretical calculation.

Summary • We have theoretical tool to study Compton at ~1% • Further work is need to compare theory and experiment.