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Shower Energy Scale Systematics

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

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Shower Energy Scale Systematics

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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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