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

2. Contents PE Rescaling PE Rescaling Cosmic ray rate Cosmic ray rate

3. PE Scale Problem: Problem: PE scale * in data not constant over Milagro’s lifetime PE scale * in data not constant over Milagro’s lifetime Major reason  Different calibrations 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. MC PE scale was in best agreement with calibration v601. That calibration version was produced with the new bright laser 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. 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 Reason for the change of the PE scale Imperfect filter-wheel calibration Imperfect filter-wheel calibration Change of laser Change of laser And many other reasons Andy and the people that were taking the calibrations know 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 We are now rescaling everything : Rec data, raw data, MC data to match the v501 calibrations Rescaling enabled by default Rescaling enabled by default Formula applied Formula applied PEs rescaled = PEs original (1+factor*log10(PEs original ) PEs rescaled = PEs original (1+factor*log10(PEs original ) For Rec data, factor depends on calibration version that produced the data 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. 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. 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 The cut was selected to keep only the top 500Hz of data

8. PE Rescaling

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

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

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

12. PE Rescaling mxpe, x2, A4 are now more stable between epochs 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 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 o Mirror cover = 100% diffuse reflections o 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 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. This could affect the flux calculation and possibly the energy estimation.

16. Nfit cosmic ray rates Out of ideas on what causes the problem Out of ideas on what causes the problem Factors ruled out 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 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 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 MC 0.5 air under cover Plots have same normalization and scale

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

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

20. Nfit_2layer vs time