Status Update on the Status Update on the Monte Carlo SimulationMonte Carlo Simulation

Vlasios VasileiouVlasios Vasileiou

April 20-21, 2007April 20-21, 2007

Milagro Collaboration MeetingMilagro Collaboration Meeting

ContentsContents

PE RescalingPE Rescaling Cosmic ray rateCosmic ray rate

PE ScalePE Scale

Problem:Problem: PE scalePE scale** in data not constant over in data not constant over

Milagro’s lifetimeMilagro’s lifetime Major reason Major reason Different calibrations Different calibrations

**PE scale relation between true number of pes in a hit with number of pes derived from the TOT method / MC

PE ScalePE Scale

MC PE scale was in best agreement MC PE scale was in best agreement with calibration v601. with calibration v601.

That calibration version was That calibration version was produced with the new bright laser produced with the new bright laser

Calibration v601 predicts numbers Calibration v601 predicts numbers of PEs closer to the true numbers of of PEs closer to the true numbers of PEs, than the other calibrations. PEs, than the other calibrations.

PE RescalingPE Rescaling

Reason for the change of the PE Reason for the change of the PE scalescale Imperfect filter-wheel calibrationImperfect filter-wheel calibration Change of laserChange of laser And many other reasons Andy and the And many other reasons Andy and the

people that were taking the calibrations people that were taking the calibrations knowknow

PE RescalingPE Rescaling

We are now rescaling everything : We are now rescaling everything : Rec data, raw data, MC data to Rec data, raw data, MC data to match the v501 calibrationsmatch the v501 calibrations

Rescaling enabled by defaultRescaling enabled by default Formula appliedFormula applied

PEsPEsrescaledrescaled = PEs = PEsoriginaloriginal (1+factor*log10(PEs (1+factor*log10(PEsoriginaloriginal)) For Rec data, factor depends on calibration version that For Rec data, factor depends on calibration version that

produced the dataproduced the data Andy calculated the appropriate factor needed to match Andy calculated the appropriate factor needed to match

the median of the mxpe distributions.the median of the mxpe distributions.

PE RescalingPE Rescaling

Plotted the percentiles of mxpe, X2, Plotted the percentiles of mxpe, X2, A4 from Rec data vs MJulianDate A4 from Rec data vs MJulianDate using a fluctuating ntop cut.using a fluctuating ntop cut.

The cut was selected to keep only The cut was selected to keep only the top 500Hz of datathe top 500Hz of data

PE RescalingPE Rescaling

PE RescalingPE Rescaling

Green 75% percentileRed 50% percentile (median)Black 25% percentile

Before After

Dashed lines come from the Rescaled MC using the same cut.

PE RescalingPE Rescaling

Green 75% percentileRed 50% percentile (median)Black 25% percentile

Before After

Dashed line comes from the Rescaled MC using the same cut.(it’s the wiggly one)

PE RescalingPE Rescaling

Before

After•A4 calculated with nfit_2layer•For the pre-outrigger era, A3 is plotted

PE RescalingPE Rescaling

mxpe, x2, A4 are now more stable mxpe, x2, A4 are now more stable between epochsbetween epochs

MC Cosmic Ray rates MC Cosmic Ray rates

As showed in previous collaboration As showed in previous collaboration meeting, the MC predicts a lower meeting, the MC predicts a lower cosmic ray rate than data vs ntop, cosmic ray rate than data vs ntop, ntop2, nfit cutsntop2, nfit cuts

g4sim 2.1, 5GeV-500TeV

0

0.2

0.4

0.6

0.8

1

1.2

10 40 70 100 130 160 190

nfit cut

Rate

MC

/Rate

Data

Mirror cover

100% air under cover

50% air under cover

0% air under cover

Effects of air under coverEffects of air under coverg4sim 2.1, 5GeV-500TeV

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

10 40 70 100 130 160 190

Ntop2 cut

Rate

MC

/Rate

Data

Mirror cover

100% air under cover

50% air under cover

0% air under cover

g4sim 2.1, 5GeV-500TeV

0

0.5

1

1.5

2

2.5

10 40 70 100 130 160 190

Ntop cut

Rate

MC

/Rate

Data

Mirror cover

100% air under cover

50% air under cover

0% air under cover

o Mirror cover = 100% diffuse reflections

o Reflected light doesn’t produce hits that participate in the fit

Cosmic ray rate vs nfit Cosmic ray rate vs nfit cutcut

For most of the nfit cut range, the For most of the nfit cut range, the MC predicts a cosmic ray rate of MC predicts a cosmic ray rate of about ~40-60% of the one from dataabout ~40-60% of the one from data

This could affect the flux calculation This could affect the flux calculation and possibly the energy estimation. and possibly the energy estimation.

Nfit cosmic ray ratesNfit cosmic ray rates

Out of ideas on what causes the Out of ideas on what causes the problemproblem Factors ruled outFactors ruled out

reflections from the cover, noise, time jitter, reflections from the cover, noise, time jitter, thrown energy range, corsika hadronic thrown energy range, corsika hadronic model, PMT corrections, using different model, PMT corrections, using different spectral indices & fluxes from different spectral indices & fluxes from different experimentsexperiments

Made hit and fit maps to see if there Made hit and fit maps to see if there is something funny with the MCis something funny with the MC

Fit Maps (no nfit cut)Fit Maps (no nfit cut)

Data run 6662Post-repair

MC 0.5 air under cover

Plots have same normalization and scale

Fit Maps (nfit>80)Fit Maps (nfit>80)

Data run 6662Post-repair

MC 0.5 air under cover

Plots have same normalization and scale

Cosmic ray rates vs nfit Cosmic ray rates vs nfit cutcut

Fit maps look similarFit maps look similar No features present in just one of the No features present in just one of the

mapsmaps Any ideas why the rates are smaller Any ideas why the rates are smaller

in the MC?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 Used the same Epoch 5 analysis to

calculate the ratescalculate the rates Cross-talk?Cross-talk?

Nfit_2layer vs timeNfit_2layer vs time