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PID Capabilities in Hall C

This talk provides an overview of the SHMS PID performance during the Spring and Fall 2018 experiments, focusing on the calorimeter and Cherenkov cut efficiencies, pion contamination, and other issues.

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PID Capabilities in Hall C

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  1. PID Capabilities in Hall C Simona Malace Jefferson Lab Talk at the J/psi Collaboration Meeting, October 26 2018

  2. Overview • SHMS PID performance during Spring 2018 (E12-10-002) •  SHMS Calorimeter and NGC and HGC response •  Pion contamination for standard cuts •  Calorimeter and Cherenkov cut efficiencies •  Issues • SHMS and HMS PID performance during Fall 2018 (Kaon LT experiment) •  SHMS and HMS Calorimeter and HGC response •  Pion contamination for standard cuts •  Issues

  3. SHMS PID during E12-10-002 (F2) – Spring 2018 Run 2788: SHMS at E’ = -2.1 GeV and theta = 33 deg All, just a delta cut HGC: C4F8O at 1 atm NGC: CO2 at 1 atm Pions will not produce Cherenkov light in neither gas for run 2788 + HGC > 2. + NGC > 2. Etottracknorm

  4. SHMS PID during E12-10-002 (F2) Calorimeter is used here to select electrons mostly NGC NPE HGC NPE HGC mean NPE ~ 16 NGC mean NPE ~ 22

  5. SHMS PID during E12-10-002 (F2): The Inefficiency in the “Middle” of Acceptance Calorimeter is used here to select electrons mostly NGC > 2. NGC > 4. delta • NGC: > 2. / > 4. npe cut leads to at most 2.5 % / 4 % additional inefficiency around delta ~ 0

  6. SHMS PID during E12-10-002 (F2): The Inefficiency in the “Middle” of Acceptance Calorimeter is used here to select electrons mostly NGC > 2. HGC > 1. NGC > 4. HGC > 2. HGC > 4. delta delta • HGC: > 1. / > 2. / > 4. npe cut leads to at most 2 % / 5 % / 13% additional inefficiency around delta ~ 0 • NGC: > 2. / > 4. npe cut leads to at most 2.5 % / 4 % additional inefficiency around delta ~ 0

  7. SHMS PID during E12-10-002 (F2): Pion Contamination (- Polarity) Run 2788: SHMS at E’ = -2.1 GeV and theta = 33 deg (ELREAL trigger) All NGC > 2. NGC < 2. NGC < 2. rescaled Etottracknorm

  8. SHMS PID during E12-10-002 (F2): Pion Contamination (- Polarity) Run 2788: SHMS at E’ = -2.1 GeV and theta = 33 deg (ELREAL trigger) All NGC > 2. NGC < 2. NGC < 2. rescaled Pion contamination Etottracknorm NGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 0.3 %

  9. SHMS PID during E12-10-002 (F2): Pion Contamination (- Polarity) Run 2788: SHMS at E’ = -2.1 GeV and theta = 33 deg (ELREAL trigger) All NGC > 2. NGC < 2. NGC < 2. rescaled Pion contamination Etottracknorm Etottracknorm HGC > 1. && Etottracknorm > 0.7 Pion Contamination: ~ 0.5 % NGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 0.3 %

  10. SHMS PID during E12-10-002 (F2): Pion Contamination (- Polarity) Run 3028: SHMS at E’ = -4.4 GeV and theta = 25 deg (ELREAL trigger) At 4.4 GeV the pion will produce light in the HGC; pion contamination not estimated with an HGC cut * Disclaimer: the calorimeter distributions need to be better understood; I am applying a minimal set of cuts for this quick estimation of the pion contamination NGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 0.4 %

  11. SHMS PID during E12-10-002 (F2): Pion Contamination (+ Polarity) Run 2879: SHMS at +2.7 GeV and theta = 29 deg(ELCLEAN trigger) NGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 6.5 %

  12. SHMS PID during E12-10-002 (F2): Pion Contamination (+ Polarity) Run 3089: SHMS at +2.7 GeV and theta = 21 deg(ELCLEAN trigger) Run 2879: SHMS at +2.7 GeV and theta = 29 deg(ELCLEAN trigger) NGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 6.5 % NGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 5.4 %

  13. SHMS PID during E12-10-002 (F2): Calorimeter Cut Efficiency • A“clean” sample of electrons is selected with a tight NG Cherenkov cut; only those electrons that went through the part of the trigger that did not involve the calorimeter are selected (ELLO without PRLO) • Then the effect of the Etottracknorm > 0.7 cut is tested on this sample • The cut efficiency is obtained per momentum setting by extrapolating to zero pion/electron ratio

  14. SHMS PID during E12-10-002 (F2): Calorimeter Cut Efficiency • A“clean” sample of electrons is selected with a tight NG Cherenkov cut; only those electrons that went through the part of the trigger that did not involve the calorimeter are selected (ELLO without PRLO) • Then the effect of the Etottracknorm > 0.7 cut is tested on this sample • The cut efficiency is obtained per momentum setting by extrapolating to zero pion/electron ratio •  Etottracknorm > 0.7 cut efficiency is high E’ = -4 GeV Efficiency at 4 GeV: 99.7 +/- 0.1 E’ = -2.7 GeV Efficiency at 5.1 GeV: 100.5 +/- 1.9 Plots by Fernando Araiza Gonzales (F2 student)

  15. SHMS PID during E12-10-002 (F2): NG Cherenkov Cut Efficiency • A “clean” sample of electrons is selected with a tight calorimeter cut; only those electrons that have made it through the ELHI trigger leg (no Cherenkov input) are used • The NGC npe > 2. cut is tested on this sample • The cut efficiency is obtained by extrapolating to zero pion/electron ratio •  The NGC cut efficiency is high Plots by AbishekKarki (EMCstudent)

  16. SHMS PID during E12-10-002 (F2): NG Cherenkov Cut Efficiency • A “clean” sample of electrons is selected with a tight calorimeter cut; only those electrons that have made it through the ELHI trigger leg (no Cherenkov input) are used • The NGC npe > 2. cut is tested on this sample • The cut efficiency is obtained by extrapolating to zero pion/electron ratio •  The NGC cut efficiency is high NGC cut efficiency vs x (SHMS E’ = -5.1 GeV, theta = 21 deg) 2-3 % cut inefficiency at x close to zero Plots by AbishekKarki (EMCstudent)

  17. Reminder: The NGC and Its Gassy PMTs PMT 1 PMT 2

  18. Reminder: The NGC and Its Gassy PMTs PMT 1 AdcTdcTimeDiff PMT 2 AdcTdcTimeDiff PMT 3 PMT 2 PMT 1 NGC NPE per PMT • PMT 2 should be replaced; timing cuts help a lot reduce high rate background from the gassy tube but some background still left

  19. Reminder: The NGC Calibration • Ideally the calibration should be done via the identification of the single photoelectron (SPE) peak in the npe distribution • During Spring 2018 the gains of the PMTs were such that the FADC threshold (10 mV) was cutting into the SPE peak • It appeared that increasing the gains to push the SPE peak above 10 mV would lead to saturation of PMTs in beam conditions

  20. Reminder: The NGC Calibration • Ideally the calibration should be done via the identification of the single photoelectron (SPE) peak in the npe distribution • During Spring 2018 the gains of the PMTs were such that the FADC threshold (10 mV) was cutting into the SPE peak • It appeared that increasing the gains to push the SPE peak above 10 mV would lead to saturation of PMTs in beam conditions • The calibration is more painful

  21. Reminder: The NGC Calibration • Ideally the calibration should be done via the identification of the single photoelectron (SPE) peak in the npe distribution • During Spring 2018 the gains of the PMTs were such that the FADC threshold (10 mV) was cutting into the SPE peak • It appeared that increasing the gains to push the SPE peak above 10 mV would lead to saturation of PMTs in beam conditions •  When NGC is used again this should be revisited; maybe one can find a way to preserve the SPE in the FADC distribution

  22. SHMS PID during Kaon LT: the HGC • Since Spring 2018 the HGC mirror positions have been slightly adjusted* • We see a more than 30 % increase in the NPE yield in some regions of the acceptance (it is not a calibration artifact, the effect is clear when comparing amplitudes directly for Spring and Fall 2018 runs*) NPE

  23. SHMS PID during Kaon LT: the HGC • Since Spring 2018 the HGC mirror positions have been slightly adjusted* • We see a more than 30 % increase in the NPE yield in some regions of the acceptance (it is not a calibration artifact, the effect is clear when comparing amplitudes directly for Spring and Fall 2018 runs*) • The inefficiency close to delta of zero, however, got worse: from run 4721 it’s a 25% relative* inefficiency for a npe cut > 2. delta NPE NPE delta

  24. SHMS PID during Kaon LT: the HGC Calibration • Calibration done with cosmic data • PMTs are pretty well gain matched PMT 2 PMT 1 PMT 3 PMT 4 Amplitude (mV) Amplitude (mV)

  25. SHMS PID during Kaon LT: the HGC Calibration • Calibration done with cosmic data • The calibration coefficients agree very well with those obtained by the Regina group (fitting a PMT response function to beam data) PMT 1 PMT 2 PMT 3 PMT 4 npe npe

  26. SHMS PID during Kaon LT: Pion Contamination (- Polarity) Run 4721: SHMS at E’ = -2. GeV and theta = 20.5 deg (3/4 trigger) The momentum here was chosen so that the pions do not produce Cherenkov light * Disclaimer: likely overestimated; a more careful study is needed HGC > 2. && Etottracknorm > 0.7 Pion Contamination: ~ 6* %

  27. HMS PID during Kaon LT: the Cherenkov • During Spring 2018 the HMS Cherenkov was a mess

  28. HMS PID during Kaon LT: the Cherenkov • During Spring 2018 the HMS Cherenkov was a mess • Howard replaced the mirrors and readjusted the PMT positions w.r.t. mirrors •  The HMS Cherenkov is in great shape now This is now fixed HMS Cherenkov performance during Fall 2018 npe delta delta

  29. HMS PID during Kaon LT: the Cherenkov Calibration • The HMS Cherenkov PMTs have been gain matched and a calibration with cosmics has been done • Average npe yield now from electrons is ~12.5 npe Amplitude (mV)

  30. HMS PID during Kaon LT Run 4721: SHMS at E’ = -3. GeV and theta = 24.4 deg (3/4 trigger) Etottracknorm • At these kinematics the pion contamination is negligible

  31. Summary • The HMS PID are performing well • The SHMS NG and HG Cherenkovs have few issues

  32. Backup

  33. SHMS Trigger PID Legs: Fall 2018

  34. SHMS Trigger PID Legs: Fall 2018

  35. SHMS Trigger PID Legs: Fall 2018

  36. SHMS Trigger PID Legs: Fall 2018

  37. SHMS Trigger PID Legs: Fall 2018 elec eff. elreal: 5041 5041 1pion rej. elreal: 58127 205741 3.53951 Details: elec eff. prlo: 5019 5041 0.995636pion rej. prlo: 113502 205741 1.81266 elec eff. prhi: 4992 5041 0.99028pion rej. prhi: 53755 205741 3.82738

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