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Systematic Errors in Shower Energy Scale Reconstruction for Neutrino Detectors

Explore systematic errors in shower energy scale reconstruction for neutrino detectors. Calculate total systematic error, evaluate PMT gain miscalibration, light level miscalibration, and more. Investigate remaining effects.

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Systematic Errors in Shower Energy Scale Reconstruction for Neutrino Detectors

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  1. Shower Energy Scale Systematics Philip Rodrigues Oxford Group Meeting 26 April 2007

  2. Aims • Calculate total syst error on shower energy scale • Contributions: • PMT gain miscalibration • Light level miscalibration • Random miscalibrations • Dead channels, noise • Need ND and FD. Only ND so far

  3. Method • Reconstruct reroot files with nominal and altered settings • Follow showers from each true nu in fid vol • Sum shower energy in mips

  4. PMT gain • Only relevant to MC, which does this: • Divide by gain to do deposited energy  PE • Multiplies by gain to do PE  ADC • So it should cancel, but PE counting and randomness can change it

  5. Sanity Check • Change gains by factor 5, to make sure this is doing what we think it is Seems reasonable: Gain calib should cancel in limit of high #photons/PEs (ie low gain regime), but quantization effects occur if low #photons/PE (ie high gain)

  6. Effect of Random Seed • Alter random seed in PhotonTransport/DetSim • Reco same events

  7. Rolling • Effect of random seed dominates effect of gain • To overcome this: • Take moderate # of fiducial events • Reroll each event 500 times • Average the shower energy over all rerollings • For error, use error on the mean (not RMS of distribution)

  8. Result • Still no systematic shift • Low energy events have big spread – why?

  9. Reconstruction Effects • Weird event:

  10. Hybrid method • Reroll events as before • Now add binning – take weighted mean in 0.5 GeV bins in true shw E • Could almost believe there’s a systematic effect in gain up • Will average over all events to get one number

  11. Light level • Should be simpler – 5% change in GeVmip calibration should give 5% change in shw energy • Lo and behold!

  12. Still to do • Finish off gain systematic • Decide what to do with badly reco’d evts • Get one number to characterize the error • Repeat for FD • Check light level for FD • Investigate remaining effects (dead channels, noise, random miscalibrations…)

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