Calibration of the new Particle Identification Detector (PID)
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Calibration of the new Particle Identification Detector (PID)
Tom Jude, Derek Glazier, Dan Watts
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Talk overview
• A brief description of the new PID.
• Energy corrections for light loss in the PID.
• Calibration of energy deposition in the PID by comparison with simulated data.
• Particle identification and reconstruction of missing masses using the PID.
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Description of the PID• The PID is a cylinder of 24 plastic scintillators, surrounding the target and parallel to the beam.
• The PMTs for light collection from the plastic scintillators is upstream from the target.
• The PID can be used for particle identification via E-E plots (Figure 1).
Figure 1. Example of a E-E plot Figure 2. PID cross-section
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Correcting for light loss in the PID
• At forward angles, protons stop further from the PMTs in the PID elements.
• Less scintillation light from these protons reach the PMT.
Figure 3. Light loss corrections. Mean energy of minimum ionised pions vs. . Red points are without light loss correction, blue with the correction. A 3rd order polynomial was fitted to the data.
•A cut on the minimum ionised pions that punch through the Crystal Ball was made.
•The mean energy was plotted
as a function of •A 3rd order polynomial was fitted and the parameters used to correct for light loss in the Crystal Ball reconstruction software.
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Calibration of the PID
• A Geant4 simulation was used to simulate Pion and Proton detection.
• E-E plots of the energy in the Crystal Ball Vs. the energy in the PID.
• Sliced into 50 intervals across the Crystal Ball energy axis.
• Projected as one dimensional histograms onto the PID axis.
• Two Gaussian functions fitted, giving peaks over the pions and protons.
Figure 4. A projected slice of the E-E plot of experimental data. First peak is the slice from the pion curve, second peak the slice from the proton curve. Two Gaussian peaks are fitted to the data.
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Figure 5. Means of the proton peaks from projections. Experimental Vs. simulated data.
/MeV
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Figure 6. E-E plot at forward angles where a curve of kaons can be seen.
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Graphically cutting on the E-E plots
Figure 7. Graphical cuts on proton, kaon and pion curves
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Strange meson production
• The reaction channels in Equations 1 and 2 were reconstructed using the graphical cuts on the previous slide (Figure 6).
• mesons were identified from their decay into two photons.• Other decay channels were avoided by vetoing on charged particles.
(1)
(2)
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First look at K+ in the Crystal Ball
Figure 8. Missing mass measurements for strange decay channels. In (a),(b) and (c) red lines are simulated data.
(a) K+ missing mass
(b) K+ and 0 combined missing mass
(b) angle between measured and expected recoil from missing 4 momentum
(c) K+ missing mass Vs. K+, 0 combined missing mass
Expected missing masses:
= 1193 MeV
= 1116 MeV
n = 940 MeV
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Summary
• As a first approximation, the PID was calibrated using simulated data.
• Energy corrections for light loss in the PID were incorporated into the reconstruction software and shown to enhance E-E plots.
• Graphically cutting on E-E plots and vetoing charged particles successfully reproduced missing masses from strange meson production channels.