G0 Apr 07 Update

1
G0 Apr 07 Update
D. Beck UIUC Apr. 07

• All data taking completed
• Hydrogen 362, 687 MeV
• 90 C, 100 C collected, respectively at 84
  polarization
• 170 C proposed at 75 polarization
• Deuterium 362, 687 MeV
• 65, 45 C collected, respectively 84
  polarization
• Backgrounds
• very clean hydrogen elastic signal all
  backgrounds total 5-10
• deuterium has backgrounds up to 20 in elastic
• mostly randoms from real pions ? accidental
  Cherenkov
• measure concurrently

2
Electron Yields
(quasi) elastic electrons
LH2, 678 MeV
LH2, 687 MeV
LH2, 362 MeV
LD2, 362 MeV
LD2, 687 MeV
3
Beam Specifications
Parity qualityData from December
Suleiman, Bailey, Schaub, Pitt.Mammei BCMBPM
calibrations
- 2 ns beam structure, 84 polarization- Beam
Energy (Jones) Apr 17th 2006 685.57 /-
0.92 MeV Sept 27th 2006 684.86 /- 0.92
MeV Dec 19th 2006 689.61 /- 0.93 MeV
Mar 14th 2007 689.41 /- 0.93 MeV Low
energy (e-p from HallA)Two heliciy
states IHWP in and out
4
Quartz PMTs

• Aerogel Cherenkov counters for p/e separation
  (LD2)

• 4 - 5 in. PMTs each
• boroscilicate glass very sensitive to neutrons
• replace with quartz
• beam current for LD2 limited by
• high real p rates ?
• (neutron) Ch. accidentals
• quartz tubes allow increase in effective electron
  efficiency by x2
• current limits 20 mA (35 mA) at 687 (362) MeV
• final tubes installed over Xmas break

boroscilicate
quartz
Note difference in vertical scales
5
Preliminary Raw Elastic Asymmetries
LH2, 687 MeV
LH2, 362 MeV
LD2, 687 MeV
LD2, 362 MeV
6
Deadtime/Randoms Corrections
Deadtimes ()

• Deadtime corrections
• Simulated the complete electronics chain (P.
  Pillot)

LH2, 687 MeV
LH2, 687 MeV, 60 mA 7 LH2, 362 MeV, 60 mA
6 LD2, 687 MeV, 20 mA 9 LD2, 362 MeV, 35
mA 13
LH2, 362 MeV
(work in progress)

• Randoms corrections
• LH2 randoms small
• LD2 randoms significant, esp. inelastic el.
• measure directly! (Breuer)

7
Expected G0 Results

• November projections (including extension)
• goals for charge accumulation met

8
G0 362 MeV LH2 Transverse Asymmetry

• BLINDED online results
• no corrections for h.c. beam parameters,
  deadtime,

Transverse Elastic
P R E L I M I N A R Y
Octant