Preliminary Analysis Results of PoGO Argonne Beam Test

1
Preliminary Analysis Results of PoGO Argonne Beam
Test

• December 10, 2003
• Tsunefumi Mizuno
• mizuno_at_SLAC.Stanford.EDU

2
Data Files

• 212 data files and the log (txt and pdf format)
  can be obtained through the web
• http//www.slac.stanford.edu/mizuno/PoGO/Argonne/
  index.html
• Digitized data files, where peak voltage is
  converted in 10 bit integer will be used in the
  following analysis.
• Data files are also available via ftp ftp as
  'anonymous' to ftp.slac.stanford.edu then "cd
  groups/astro_gam/PoGO/Argonne

3
Run Summary

• Coincidence Trigger (every 15 degree)
• run048-073 83.5 keV run
• run106-149 60.2 keV run
• run164-190 73.2 keV run
• Ch4 Trigger (every 30 degree, does not cover the
  whole azimuth angle)
• run191-197 73.2 keV run
• run210-212 83.5 keV run
• Calibration Run
• run088,090-096 83.5 keV run
• run090-105,150-156 60.2 keV run
• run157-163 73.2 keV run
• For more details, please read the log in
  http//www.slac.stanford.edu/mizuno/PoGO/Argonne/
  index.html.
• We also took the BG data but does not use them in
  this preliminary analysis report. BG is small and
  does not affect the results very much.

4
Calibration Run

• Fit data with gaussian linear function
• Use channel/energy conversion factors for 73.2
  keV run in the following analysis. Conversion
  factors for 83.5 keV run and 60.2 keV run are
  consistent with them within 2.
• ch1 p326.5, sigma34.9 (FWHM25.1), f4.46
• ch2 p331.5, sigma32.3 (FWHM22.9), f4.53
• ch3 p334.9, sigma39.5 (FWHM27.7), f4.58
• ch4 p317.7, sigma41.5 (FHWM30.7), f4.34
• ch5 p350.9, sigma49.1 (FHWM32.9), f4.79
• ch6 p326.0, sigma35.5 (FHWM25.6), f4.45
• ch7 p377.2, sigma43.6 (FHWM27.2), f5.15

5
Definitions

• We defined that xy plane is normal to the
  scintillator principle axis.
• Scintillators are numbered from 1 to 7. Central
  scintillator is number 4.
• Beam goes from z to -z. Polarization vector is
  along x-axis.
• We rotated the detectors. When we rotate them by
  30 degree, scintillator number 2 is along the y
  axis.

y
30degree
polarization vector
1
2
3
4
5
x
Beam Direction
6
7
6
73.2 keV Ch4 Trigger Run (1)
Event selection criteria Detection threshold2
keV 2 scintillators are with hit (one hit in
central scintillator) depE4lt40keV,
depE4lt0.5totE 45 keV lt totE lt 100 keV
Total deposit energy seems to be 70 keV, a
little bit smaller than the beam energy.
7
73.2 keV Ch4 Trigger Run (2)
ch3
ch7
ch5
Modulation Factor (1650-650)/(1650650) 43
ch1
ch2
ch6
8
Trigger Efficiency (1)

• During the beam test, we found that trigger
  efficiency is not 100 for coincidence trigger
  run and it varies among channels. E.g.,
  efficiency of ch6 seemed to be 2/3 of others.
• To obtain unbiased events, we performed ch4
  trigger run, and the results were shown in page
  7. By comparing them with coincidence trigger run
  of the same energy and rotation angle, we can
  evaluate the relative trigger efficiency of each
  channel.

9
Trigger Efficiency (2)

• Use 73.2 keV runs.
• Efficiency of ch7 is normalized to 1.
• Errors shown are statistical errors only.
• Fitting by constant (dof5)
• ch10.843-0.017, chi26.6
• ch20.979-0.021, chi28.7
• ch30.987-0.021, chi26.1
• ch50.803-0.018, chi25.7
• ch60.621-0.013, chi27.6
• Chi2/dofgt1. Probably there are systematic errors
  comparable to statistical ones.

ch2
ch3
ch1
ch5
ch6
10
73.2 keV Coincidence Trigger Run(1)

• Selection criteria are the same as those for ch4
  trigger run.

• Total deposit energy seems to be a little bit
  smaller than beam energy.
• We observe a small dip in energy deposit in
  scintillator number 4 (around 10 keV).

11
73.2 keV Coincidence Trigger Run(2)

• Selection criteria are the same as those for ch4
  trigger run.
• Trigger efficiency is not collected.
• Normalized based on the number of triggers.

ch3
ch2
ch7
ch5
ch1
ch6
12
73.2 keV Coincidence Trigger Run (3)

• Selection criteria are the same as those for ch4
  trigger run.
• Trigger efficiency is collected.
• Normalized based on the number of selected events.

ch3
ch2
ch7
ch1
ch5
ch6

• MF(2400-1000)/(24001000)41
• Small (but statistically significant) difference
  between ch1/ch7, ch2/ch6, and ch3/ch5. Due to
  geometry? Error of trigger efficiency?

13
83.5 keV Coincidence Trigger Run(1)

• Selection criteria Eth2keV, 2hits (one in
  central scint.), depE4lt45keV, depE4lt0.5totE,
  55keVlttotElt110 keV.
• Trigger efficiency is not collected.
• Normalized based on the number of triggers.

ch3
ch2
ch7
ch5
ch1
ch6
14
83.5 keV Coincidence Trigger Run (2)

• Selection criteria are the same as those in the
  previous page.
• Trigger efficiency is collected.
• Normalized based on the number of selected events.

ch3
ch6
ch7
ch5
ch2
ch1

• MF(2400-1000)/(24001000)41
• Small difference between ch1/ch7, ch2/ch6, and
  ch3/ch5.

15
60.2 keV Coincidence Trigger Run(1)

• Selection criteria Eth2keV, 2hits (one in
  central scint.), depE4lt35keV, depE4lt0.5totE,
  35keVlttotElt90 keV.
• Trigger efficiency is not collected.
• Normalized based on the number of triggers.

ch3
ch2
ch7
ch5
ch1
ch6
16
60.2 keV Coincidence Trigger Run (2)

• Selection criteria are the same as those in the
  previous page.
• Trigger efficiency is collected.
• Normalized based on the number of selected events.

ch3
ch1
ch2
ch7
ch5
ch6

• MF(2400-1000)/(24001000)41
• Difference between ch1/ch7, ch2/ch6 and ch3/ch5.
  Somewhat larger than those seen in
  73.2keV/83.5keV runs.

17
Summary

• We applied preliminary event selection criteria
  to data. Modulation factor for ch4 trigger run of
  73.2 keV is 40-45 (pages 6 and 7).
• We evaluated the rigger efficiency of ring
  scintillators. There could be some systematic
  errors, but they are small and comparable to
  statistical ones (pages 8 and 9).
• We took the trigger efficiency into account for
  coincidence trigger runs and obtained clear
  modulation curves. MF (40-45) does not depend on
  the beam energy very much and is consistent with
  that of ch4 trigger run (pages 10-16).
• We observe small difference between ch1/ch7,
  ch2/ch6 and ch3/ch5. It could be due to geometry
  and/or errors of trigger efficiency (pages 12, 14
  and 16).
• We also found some strange features (probably not
  a big problem)
• Total energy deposition is 5 smaller than the
  beam energy.
• We observed small dip in energy deposition of ch4
  (central scintillator) for coincidence trigger.
• Future Plan
• Understand features mentioned above (if
  possible).
• Improve event selection.
• Compare data with simulation prediction.