January 30, 2014 - Special Theory Meeting

Meeting Logistics

Thursday, January 30th 9am EST

JLAB Meeting Room TBD

Remote call-in information TBD

BACKGROUND FOR THEORISTS

OUR EXPERIMENTAL PROGRAM

To precisely measure scattering asymmetry of spin polarized electrons from thin pure Z foils

Accessible energy range is about 3 to 8 MeV

Targets on hand are gold, silver, copper foils of varying thickness, but can install others readily

Measure polarimeter systematics with goal <0.5%

OUR SIMULATION PROGRAM

Build GEANT4 model of polarimeter and benchmark detector response against measurement

Implement physics (cross-section, Sherman function, spin transfer functions) provided by theory

Develop ab initio simulation dependence of asymmetry on target thickness (multiple scattering, radiation effects, etc) to measurement

By calibrating model to experimental data predict zero-thickness asymmetry with high precision <1%

DESIRED THEORY PROGRAM

Provide physics tables for simulation (cross-section, Sherman function, spin transfer functions)

Describe theoretical basis, corrections, uncertainties

Advise which measurements may be best tests on leading corrections or limit absolute knowledge of physics

Consider calculation to improve uncertainty in physics below 1%

Questions (Please follow format shown)

Question #1 (Joe 1/13/2014)

Coulomb screening is a leading effect for electron energies <1 MeV, and finite nuclear size is a leading effect for energies >10MeV (when DeBrogile wavelength is comparable to nuclear radius). Although our polarimeter is optimized for 5MeV we can operate with beam energies typically from about 3-8 MeV. What is the size of the uncertainty on the corrections in this energy range and for Z we use such as gold, silver, copper? Are we sensitive enough in this region to perform a test on the uncertainty of the physics calculations, e.g. using suitable Z or extending the energy reach?

Question #2 (Joe 1/15/2014)

Is the biggest uncertainty in the theoretical calculations radiative corrections? Can a sound theoretical calculation be made that calculates this contribution with relative accuracy of ~30%?

Question #3 (Who, When)

My question is...

Please copy and paste format, and so on...