Luminosity Analysis Plan Status Prim Ex Friday Meeting

Luminosity Analysis Plan & Status Prim. Ex Friday Meeting October 7, 2005 Dan Dale

Analysis efforts • • • Electron counting (absolute flux) Pair spectrometer (relative tagging ratios) TAC (absolute tagging ratios) Target thickness Known cross sections (pair production, Compton)

Status of electron counting: • Primary technique: -clock trigger, sample tagger electron rate essentially done. • Secondary technique: -HYCAL trigger, sample tagger rate out of time with trigger Deemed lower priority.

Pair Spectrometer Analysis Plan • Stability of relative tagging ratios over time -First pass done for carbon production runs. -Needs to be redone without beam trips. • Study upstream scraping from pair spectrometer and target out runs -done. Looks ok. • Different radiator thicknesses -Does this effect relative tagging ratios/beam profile? -first pass done. No effect detectable. • Study effect of electron-electron bremsstrahlung (radiative Moller) in tagger -Marianna

Stability of relative tagging ratios

Radiator A B B B

TAC Analysis Plan • Resolve discrepancy in tagging ratios obtained by taking 1 versus multiple tagger hits (2% problem). DONE. • Collimator studies: out, 8. 6 mm 12. 7 mm -How much are we cutting beam with photon collimator? -What are the downstream consequences of scraping?

TAC Analysis Plan • HYCAL moved around a few mm -How much is HYCAL central hole cutting measured tagging ratios? Relevant runs: 4287 x=4. 02 4288 x=0. 0, y=+0. 49 4289 x=0. 0, y=-7. 095 4290 x=2. 0, y=0. 0

TAC Analysis Plan • • Collimator moved a few mm left and right -How much are we cutting beam with photon collimator? -What are consequences scraping? (x=-7 mm to +8 mm) Beam purposely mis-steered -Impact of beam position on tagging ratios Pair Spectrometer magnet on, off, low (900 Amps) -Effects of upstream scraping Consistency check of tagging ratios over time Effect of beam current on tagging ratios -40 -120 p. Amps (+300 p. Amps) Effect of leakage current (particularly Hall C) on -tagging ratios -electron counting Target photon absorption Radiative Moller

*TAC analysis algorithms established and ready to go. *Tagging ratios on a run by run basis being compiled.

Radiative Moller Two concerns: • Energy reconstruction • Flux determination

Radiative Moller and Photon Energy Determination

Radiative Moller and Flux. TAC Investigation Radiative Moller contributes here

Radiative Moller and Flux. Investigation with Pair Spectrometer

Upcoming priorities (1) Finish electron counting, including beam trips. (2) TAC analysis. (3) Pair spectrometer analysis. In parallel: Theoretical calculations of pair, Compton cross sections.

Plans on cross section calculations • Alexandr Korchin (Kharkov) has submitted a calculation plan (available upon request). It includes (1)Bethe-Heitler (modified by nuclear form factor). Ready to program. (2)Virtual Compton scattering. Model under development. (3)Radiative effects. (4)Atomic screening. (5)Electron field pair production.