E04007 p0 electroproduction near threshold

1
E04-007p0 electroproduction near threshold

• Hall A run coordinator report
• April 1st 2008 April 8th 2008
• Alexandre Camsonne

2
Experiment setup

• Electroproduction near threshold
• Missing mass technique detecting electron in HRS
  and low momentum protons with BigBite to
  reconstruct the p0
• First use of the hadron package with wire chamber

3
Detector commissioning

• DAQ checkout
• Detector checkout
• Wire chamber
• HRS
• New tracking code
• Helium Balloon setting
• Rate acceptance optimization

4
Beam tune

• Compton chicane beam looks pretty good
• Helicity checks
• Beam polarization
• Wien Angle set at 40 degrees
• Moeller
• Beam position pretty stable
• Alignment checked with target with hole
• No beam deflection for Big Bite at full current

• Run without raster
• Cell have 1 inch diameter

5
DAQ

• VME V767
• Noticed an issue of MWDC with V767, events empty
  for no apparent reason even at cosmics rate ( did
  not see with pulser tests )
• Switch to fastbus for MWDC ( April 2nd )
• ROC5 F1 TDC frequent errors and reboot
• ( situation improved when Bryan increased buffer
  )
• Might improve after tune of thresholds

6
DAQ

• Coincidence window

7
Calibration

• Efficiency
• Optimization of focal plane
• Optics
• Sieve
• Bigbite sieve
• Calibration
• Ta
• C
• H elastic

8
Big bite trigger scintillator calibration
9
HRS acceptance optimization
10
Bigbite wire chamber

• Operating fine
• One part of chamber disabled might be a broken
  wire. Short wire and edge of acceptance, we hope
  to be able to continue to run this way.
• Once tracking code works fine, we will compare
  the difference before and after the problem
• Spare chamber being repaired

11
Bigbite wire chamber
1500 V
1550 V
In process of finding optimal running
conditions Efficiency vs background Can be
thoroughly studied when tracking fully operation
12
Done this week

• Target cooldown ( both loops use less than 10 g
  og flow)
• Switch to fastbus
• Calibration data
• Production data
• Kin A and Kin B
• Moeller around 66 polarization

13
Issues resolved

• Target both loop can stay cool. Very few power
  from beam.
• VDC U2 plane TDC change fixed inefficiency
• Noise issue MWDC ( grounding )
• DAQ switch

14
Unresolved Issues

• Being worked on
• Tracking efficiency as function of HV and
  threshold
• Helicity ( MPS mistakenly flipped will change
  back at next down )
• Correlation beam trip / Bigbite trips
• Spare chamber being worked on

15
Beam use

• Scheduled hours 151 hours
• ABU 40.3
• BANU Fastbus switch, Wire Chamber work,
  detector HV trips, DAQ crash ( ROC 5 ), target
  and momentum changes
• ACC availability 68

16
Plan

• Production with optimized thresholds
• Additional calibration data
• Detector in reasonable state
• Still optimizing
• Still some parameters can be tweaked for the most
  difficult kinematics
• ( HRS, time windows, thresholds ) give margin for
  handling rates

Conclusion