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Status Update on the Monte Carlo Simulation

Status Update on the Monte Carlo Simulation. Vlasios Vasileiou April 20-21, 2007 Milagro Collaboration Meeting. Contents. PE Rescaling Cosmic ray rate. PE Scale. Problem: PE scale * in data not constant over Milagro’s lifetime Major reason  Different calibrations

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Status Update on the Monte Carlo Simulation

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  1. Status Update on the Monte Carlo Simulation Vlasios Vasileiou April 20-21, 2007 Milagro Collaboration Meeting

  2. Contents • PE Rescaling • Cosmic ray rate

  3. PE Scale • Problem: • PE scale* in data not constant over Milagro’s lifetime • Major reason  Different calibrations *PE scale  relation between true number of pes in a hit with number of pes derived from the TOT method / MC

  4. PE Scale • MC PE scale was in best agreement with calibration v601. • That calibration version was produced with the new bright laser • Calibration v601 predicts numbers of PEs closer to the true numbers of PEs, than the other calibrations.

  5. PE Rescaling • Reason for the change of the PE scale • Imperfect filter-wheel calibration • Change of laser • And many other reasons Andy and the people that were taking the calibrations know

  6. PE Rescaling • We are now rescaling everything : Rec data, raw data, MC data to match the v501 calibrations • Rescaling enabled by default • Formula applied • PEsrescaled = PEsoriginal (1+factor*log10(PEsoriginal) • For Rec data, factor depends on calibration version that produced the data • Andy calculated the appropriate factor needed to match the median of the mxpe distributions.

  7. PE Rescaling • Plotted the percentiles of mxpe, X2, A4 from Rec data vs MJulianDate using a fluctuating ntop cut. • The cut was selected to keep only the top 500Hz of data

  8. PE Rescaling

  9. PE Rescaling Before After Green 75% percentile Red 50% percentile (median) Black 25% percentile Dashed lines come from the Rescaled MC using the same cut.

  10. PE Rescaling Before After Green 75% percentile Red 50% percentile (median) Black 25% percentile Dashed line comes from the Rescaled MC using the same cut. (it’s the wiggly one)

  11. PE Rescaling Before • A4 calculated with nfit_2layer • For the pre-outrigger era, A3 is plotted After

  12. PE Rescaling • mxpe, x2, A4 are now more stable between epochs

  13. MC Cosmic Ray rates • As showed in previous collaboration meeting, the MC predicts a lower cosmic ray rate than data vs ntop, ntop2, nfit cuts

  14. Effects of air under cover • Mirror cover = 100% diffuse reflections • Reflected light doesn’t produce hits that participate in the fit

  15. Cosmic ray rate vs nfit cut • For most of the nfit cut range, the MC predicts a cosmic ray rate of about ~40-60% of the one from data • This could affect the flux calculation and possibly the energy estimation.

  16. Nfit cosmic ray rates • Out of ideas on what causes the problem • Factors ruled out • reflections from the cover, noise, time jitter, thrown energy range, corsika hadronic model, PMT corrections, using different spectral indices & fluxes from different experiments • Made hit and fit maps to see if there is something funny with the MC

  17. Fit Maps (no nfit cut) Data run 6662 Post-repair Plots have same normalization and scale MC 0.5 air under cover

  18. Fit Maps (nfit>80) Data run 6662 Post-repair Plots have same normalization and scale MC 0.5 air under cover

  19. Cosmic ray rates vs nfit cut • Fit maps look similar • No features present in just one of the maps • Any ideas why the rates are smaller in the MC? • (or why the rates are higher in data?) • Used the same Epoch 5 analysis to calculate the rates • Cross-talk?

  20. Nfit_2layer vs time

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