X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Xiaochao Zheng University of Virginia July 22-23, 2008 Overview of the experiment, schedule Preparation Manpower Plan & Summary E Status Measurement of Deuteron PVDIS Asymmetry at 6 GeV

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Goal of the Experiment Measure PVDIS asymmetry on a deuterium target, A d, at Q 2 =1.10 and 1.90 GeV 2 to a statisical error of 3% within the approved 32 days (50 days originally requested to achieve 2%); Currently scheduled to run: Nov-Dec (about 50 calendar days) Longer running possible pending on budget outcome

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Kinematics Overview (beam time = half of requested) Commissioning: 4 days (DAQ, target/boiling test, Compton) could be down to 2-3 days if following HAPPEX-III (install leadglass) DIS Production: Resonance Measurement: 2 days

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Preparation Target: 25-cm racetrack LD2 – working with Dave A.; Beam polarimetry, Parity DAQ/Polarized source, Lumi -- shared with HAPPEX-III and PREX; DAQ – unique for the experiment

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting DAQ Overview Scaler-based, fast counting DAQ using Cerenkov and leadglass counters; Have made progress this summer on deadtime study (3 methods) and asymmetry measurement (next talk); Will install in the Right HRS August-September, parasitic testing during polarized 3He experiments, use Qasym to study deadtime/systematics; Need trigger simulation Will install in the Left HRS next spring (if not sooner). May re-arrange HRS- L leadglass blocks.

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Current leadglass detector on HRS-L: 2 equal-depth layers, 2x17 blocks each New frame: 2 layers, preshower (using HERMES blocks) + shower (using existing blocks) structure closer to HRS-R, better PID DAQ electronics (almost) identical to HRS-R This summer: lack of design/tech support, but can do this later.

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Manpower Ramesh Subedi: Nov – present Ph.D students: Xiaoyan Deng: July present Diancheng Wang: July/Aug 2008, then Jan Huai-Bo Ding (5 th year Ph.D student from TsingHua U.): Aug ~ Feb We will focus on DAQ/Trigger simulation this fall, but we also want to learn other aspects: Source/Parity DAQ/Lumi/Polarimetry... Looking forward to work with all of you!

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Backup Slides

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Physics Outcome from Reduced Beam Time

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Rescattering Background Effect depends on: How many particles will be re-scattered? — 1% near central momenta, mostly from the Q3 exit (studied by HAPPEX-H and HAPPEX-He). Whether these events carry different asymmetries? — Unlikely, most have DIS kinematics very close to central setting Expect an effect on A d at the level. Will take data at low rate and compare with simulation to pin down the effect.

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Deuteron EMC Effect? Calculations show very small effect on F 2 d : (1.2±0.5)% for x=0.25 and (1.5±0.6)% for x=0.3. Effect on the asymmetry should be much smaller – 2x10 -4 on A d using the smearing technique: W. Melnitchouk, A.W. Thomas, nucl-th/

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting An alternative option (LOI03-106): Scaler-Logic-based Fast Counting DAQ

X. Zheng, July 22-23, 2008, Hall A Parity Collaboration Meeting Two Photon Exchange Effect? TPE contribute to <1% of cross section for 1<Q 2 <2 (GeV/c) 2 Effect on the asymmetry should be even smaller. “Two-Photon Exchange in Electron-Deuteron Scattering”, J. Gunion & L. Stodolsky (SLAC), Phys. Rev. Lett. 30, 345 (1973) Cross section Two Photon Effect Experiment Q 2 (GeV 2 )