Photon BackTracker in LArSoft J. Stock, J Reichenbacher. South Dakota School of Mines and Technology. December 14, 2016. Photon Detector Sim/Reco Meeting./SNB-LowEnergy Meeting
Why do we need Photon Backtracking? ● Position Studies. The Backtracker for electronic ● Potential Calibration Source signals has been available for a long Studies time in LArSoft, but due to a lack of ● Truth disambiguation. manpower and a long tasklist the same has never been provided for Photons. As the simulation is maturing and detector designs are being finalized this has become a very important feature to add. 2 J. Stock (SDSMT 12/14/2016)
Important for Radiological Background Studies to understand the detector response from various contaminants together we need to be able to disambiguate the sources of various signals. and for understanding the detector response at low energies is also crucial for other experimental goals: ● Supernova Neutrino Events ● Solar Neutrinos (day/night asymmetry) ● Low energy calibration (understanding the response to potential calibration sources) ● Understanding detection thresholds. 3 J. Stock (SDSMT 12/14/2016)
Important for Full-Blown Radiological Background Simulation Studied by Radiopurity group (desired input for example for SNB neutrino simulation or DAQ simulation): ● Ar-39 (1 Bq/kg) ● K-40 in the Field Cage and Cathode (1.4 MeV gamma) ● Co-60 in the APA (2x1.3 MeV gamma) ● Rn-222 (alphas w/~5 MeV and betas in the subsequent decay chain -as part of the late U-238 decay chain-) ● Po-210 on PDs (scintillators from Indiana have been tested and failed the established requirements, whereas additional samples directly from Eljen were tested and are well within limits. Tested by Juergen Reichenbacher using AlphaBACH, a large volume Alpha/Beta Assay CHamber at SDSMT.) 4 J. Stock (SDSMT 12/14/2016)
Obtaining the Backtracker 5 J. Stock (SDSMT 12/14/2016)
Services_dune.fcl #include "photonbacktracker.fcl" Under dunefd_services: PhotonBackTracker: @local::dunefd_photonbacktracker End of File: services.PhotonBackTracker.Delay: 260 6 J. Stock (SDSMT 12/14/2016)
How to use the Backtracker yourself: In your analysis module using the backtracker, the following sections need the lines provided: Header #include "larsim/MCCheater/PhotonBackTracker.h" Private art::ServiceHandle<cheat::PhotonBackTracker> pbt; Time permits, will publish short Wiki page/tutorial. 7 J. Stock (SDSMT 12/14/2016)
BackTracker functionality. ● The backtracker takes the OpHit and the Optical Detector the hit was registered on, and uses that to create a list of all events that contributed energy to the Optical Detector at the time of the OpHit . ● Slight forward bias in information. ● Each experiment has their own implementation of their detector response. This is reflected in the time delay between when a particle is simulated at the PDs, and when the opHit is recorded. Calibrate the backtracker. For example, in DUNE one should use: ○ services.PhotonBackTracker.Delay: 260 8 J. Stock (SDSMT 12/14/2016)
Determining the correct Delay parameter to use for the PhotonBackTracker : OpHits Created 2 split No OpHit created from SDP SDPs (Scintillation OpHits Deposited Photons) Taking the difference in time between SDPs and OpHits for a single event can be used to calibrate the detector response time in the simulation. Time (ns) Comparison of times recorded in OpDetBacktrackerRecord SDPs(ScintillationDepositedPhotons) for one 9 event and one Optical Detector vs. PeakTime for OpHits from same Event and Optical Detector.
Examples demonstrating the PhotonBackTracker works: PhotonBackTracked ɣ ’s: PhotonBackTracked muons: (w/ geometry Dune10KT_1x2x6 ) x-position (cm) x-position (cm) 2.6 MeV ɣ’s (Tl-208) 1 GeV muons isotropically produced (5 events superimposed (5 events superimposed started at x=50 and z=200) started at x=100 and z=0) 10 J. Stock (SDSMT 12/14/2016)
More examples demonstrating the PhotonBackTracker works: PhotonBackTracked muons: PhotonBackTracked muons: (w/ geometry Dune10KT_1x2x6 ) x-position (cm) x-position (cm) 1 GeV muons 0.5 GeV muons (5 events superimposed (5 events superimposed started at x=100 and z=0) started at x=100 and z=0) 11 J. Stock (SDSMT 12/14/2016)
Further Validation s n o u M V e (w/ geometry Dune10KT_1x2x6 ) G 0 2 20 GeV Muons 5 events superimposed 5 events superimposed 12 J. Stock (SDSMT 12/14/2016)
Time impact on LArSoft Issues addressed. Module Time Difference* Cleaned up old code related to UseParamaterization methods. ProdSingle 2 Sec ● A bug was introduced in the previous version for particles outside the detector Standard G4 <1 Sec volume. This has been corrected. ● This is corrected. Standard DetSim <1 Sec The PhotonBacktracker is now available in the develop branch of LArSoft and will be available Standard Reco -5.5 Min ** in the next release (v06_18_00). Conclusion: At this time it appears that the PhotonBackTracker has a minimal impact on the simulation runtime. *Times given are for 20GeV Diagonal Muons from previous slide ((With Backtracker Run Time - Without Backtracker Run Time) / # events) ** Another job was started on the GPVM I ran this test on during this stage resulting in all 4 CPUs running at full load. 13 This time is considered unreliable. J. Stock (SDSMT 12/14/2016)
Future Tests and Validations ● Full radiological study including the field cage, argon impurities, cathode and anode materials, and potential radon contaminations. ● Tests on sensitivity to low energy alphas from the radon decay chain. ● Other recommendations? 14 J. Stock (SDSMT 12/14/2016)
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