General Meeting Summary 7/12/18

DISCUSSION OF TCS PAC PRESENTATION DRAFT AND COMMITTEE QUESTIONS

• General feedback: keep answers short, avoid introducing additional material

• Suggestion: Include question from committee on the slide and present an answer for it

• Details on selected questions

• Theory - higher twist contribution: possible sign change analogous to that in SIDIS, enters with different sign, measuring two different processes allows to access experimentally

• CPS - committee questions are really not about CPS, but optimization of experiment and reduction of background in detectors, e.g.

• Background in tracker hodoscope, which is low energy photons from photon-target interactions. Solution of inserting plastic "filter" in beamline outside is a solution - heating not a problem, but need to study additional backgrounds
• Target fringe field - working on it

• Calorimeter, e.g.,

• Calibration - neutral pion decay can give in-situ calibration (as done in SANE experiment), in DVCS used hydrogen too

• PID and rates - what is the trigger rate for calorimeter?

• Need proton detection for experiment, high rate capability is important and smaller paddles or GEMs can do that. However, most important question is where to find signal - solution could be tracking (hit + direction information) through magnetic field, identify tracks pointing to the target based on momentum predicted by calorimeter based on exclusivity

• DAQ and trigger - NPS plans to use fADCs (concept similar to HPS), add cluster triggering

• Data analysis and observables:

• target spin observables, opportunistic measurements of cross section and beam spin asymmetry
• present as constraint on CFF, and in particular in relation to GPD E - translate error bar of experiment into error bar on E and compare to H (with different Ju, Jd parameterizations)