Single-Arm Compton Analysis

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Single-Arm Compton Analysis

• M. H. Wood
• University of Massachusetts, Amherst

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Motivation
As a systemic check on the p0 analysis, we want
to analyze another reaction from the same
production runs. Since the PS magnet was on, the
complete 2-arm Compton scattering is not
possible. An alternative is to measure the
Compton scattering cross section from the
scattered photon only (single-arm case). With
this goal in mind, I have analyzed the energy and
polar angle information of a single photon during
some p0 production runs. The Compton scattering
kinematics were analyzed given the scattered
photons energy and angle measured by
HyCal. This method was also tested for a few
dedicated Compton scattering runs. In that case,
the photon was selected from the two possible
clusters.
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Event Selection

• Number of clusters in HyCal gt 1
• At least 1 tagger photon from TRIGPHOTON bank
  with bit2
• Cluster energy gt 0.5 GeV
• Beamline cut
• Angular cut 0.5oltqlt1.3o
• Veto cut HYCALCLUSTER.veto lt 0

• Background reduction
• Timing cut Dt lt /- 3.5s on the timing
  coincidence (approximately /- 5 ns)

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Energy Ratio
The physical quantity used in this analysis is
the energy ratio
where Emeas is the measured cluster energy and
ECompton is the calculated energy of the
scattered photon given q and Eg.
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Number of Clusters
In order not to bias the data sample, all
clusters in an event were used to calculate the
energy ratio. I also looped over all possible
tagger photons in the analysis.
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Angular Range
0.5ltqlt0.6
0.5ltqlt0.7
0.5ltqlt0.8
0.5ltqlt0.9
0.5ltqlt1.3
0.5ltqlt1.2
0.5ltqlt1.0
0.5ltqlt1.1
In time events Sidebands
0.5ltqlt1.4
0.5ltqlt1.5
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Comparison with Dedicated Compton Run
All clusters 1 cluster 2 clusters 3 clusters
Run 5003 p0 production
Run 5150 Compton
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Veto Study
Run 5003 p0 production Yveto/YTotal98
Run 5150 Compton Yveto/YTotal46
w/o veto cut w/ veto cut
w/o veto cut w/ veto cut
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Differential Cross Sections
Compton p0 production
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Trigger Threshold Inefficiency
Run 5003 p0 production Trigger threshold -88mV
Run 5150 Compton Trigger threshold -44mV
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Trigger Inefficiency (contd)
To study the trigger inefficiency, I calculated
the normalized yields with various upper limit
on the angular range.
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New Differential Cross Sections
Compton p0 production
0.5o lt q lt 0.9o
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Conclusions

• A single-arm compton analysis was attempted to
  extracted an absolute cross section.
• The analysis was performed on p0 production runs
  as well as dedicated Compton runs.
• Due to a trigger inefficiency for Compton
  scattering during p0 runs, an absolute cross
  section cannot be extracted at this time.
• The analysis will continue using the relative
  cross section for run-to-run checks.

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Normalized Yield per Run
The data are from p0 production runs with the 12C
target.
0.5o ltq lt 0.9o
0.5o lt q lt 1.1o