June 1, 2005 Milagro Collaboration Meeting

TPed Shifting and the Crab

Curtis Lansdell

University of Maryland

History Timing calibration of outriggers

Examined outrigger TChi distributions for wandering of pedestals with time and temperature

Studied day/night and seasonal variation – how does the TChi peak change?

Found out that some PMTs have poor TChi distributions and decided to try shifting hit times to see if better distributions could be produced

Applied TPed shift method to Crab RAW data files and examined skymaps

Found good angular resolution for hard cut events

Day/Night Differences

Fit TChi peak to Gaussian for day and night data

From Dec. 19, 2004 Get difference in fits’ mean

positions and plot Small differences seen, but

typically < 0.2ns

Summer/Winter Differences

Fit TChi peak to Gaussian for day and night data

From May 19 and Dec. 19, 2004

Get difference in fits’ mean positions and plot

Here, showing only day differences

Worse statistics because May data from SAV file (probably should have used Crab RAW)

Even with worse statistics, there does seem to be larger variations (> 0.5ns)

Timing Problem

Can temperature effect be removed?

Examining TChi distributions show that timing can be off by large amounts (by as much as ~60ns in some cases)

Shifting hit times can fix this

original

ns

Measured hit time = difference between the pedestal time and the TDC time

TChi = difference between shower front fit time and the measured hit time

If the TChi peak is at positive time, the hits were usually early, else hits were late

First reconstruction of events, find TChi peak times

Store fit peak times in text files Reconstruct events again with adjusted

hit time

Fixing the Time Pedestals (offline)

TDCtimetime

TDCtimePeakTimetime )(

ns

after shift

Apply TPed Shifts to the Crab

Reconstructed same period of Crab data as done before January 2005 collaboration meeting

September 2003 to October 2004 – 416 solar days Unlike previous reconstruction, only AS and OR PMTs used in fits TPed shifting was applied

Created skymaps 2 hour maps summed up – total integration duration of 100 days

Previous Crab Results

AS+MU+OR used in fit 12 parameter MARS models used (see January 2005 collaboration

meeting talk)

  nFit>80 nFit>80, x2>2.5 MARS (on>1, off>2.5) MARS (1, 0.6) MARS (0.8, 0.8)

Significance 2.65 4.56 2.66 3.62 3.27

On Source 2212841 240608 24681 69100 61763

Off Source 2208997.25 238434.3 24275.41 68177.84 60973.69

Excess 3843.75 2173.7 405.59 922.16 789.31

FracExcess 0.00174 0.00912 0.01671 0.01353 0.01295

  nFit>150 nFit>150, x2>2.5 nFit>150, x2>5

Significance 2.4 3.13 4.19

On Source 88484 51681 12594

Off Source 87753.91 50953.76 12117.9

Excess 730.09 727.24 476.1

FracExcess 0.01 0.01 0.04

TPed Shifted Crab Results

AS+OR used in fit See memo (to be posted) “Timing Pedestal Shifting and the Crab” for

full table of the cuts examined (various nFit and x2 cuts) Same MARS cuts give higher signal to background and significance

Q-factor increase of 1.3 just from new reconstruction

MARS (1, 2.5) MARS (1, 0.6) MARS (0.8, 0.8)

Significance 3.52 4.16 4.35

On Source 22326 46340 45423

Off Source 21790.49 45426.55 44478.4

Excess 535.51 913.45 944.6

FracExcess 0.02458 0.02011 0.02124

Finding the Optimal Binsize

  0.4° 0.5° 0.6° 0.7° 0.8° 0.9° 1.0° 1.1° 1.2° 1.3°

Significance 4.1 4.11 5.22 5.23 4.64 4.65 4.66 5 4.31 4.32

On Source 149 149 285 285 431 431 431 622 942 942

Off Source 103.99 103.81 204.75 204.43 340.29 339.93 339.56 502.8 812.87 812.33

Excess 45.01 45.19 80.25 80.57 90.71 91.07 91.44 119.2 129.13 129.67

FracExcess 0.43 0.44 0.39 0.39 0.27 0.27 0.27 0.24 0.16 0.16

Looked for largest significance in hard cut events

nFit>150, x2>6, x2cx>6 (x2cx=nb2/cxPE)

marsOn>0, marsOff>0 was used by accident…

Made smoothed maps in square bins from 0.4° on a side to 1.3°

0.6°x0.6° or 0.7°x0.7° square bin size seems optimal

Angular resolution is 0.25° for 0.7° square bin

Radial Distribution

Plot radial excess distribution using unsmoothed maps from Crab coordinates

Normalized to ring area Gaussian fit centered at the Crab gives angular resolution of 0.33±0.06° Gaussian fit centered at the maximal significance (5.26σ) bin gives

0.32±0.06°

Summary

Removal of muon layer PMTs from fit and addition of TPed shifting appears to give better angular resolution for hard cut events

Scanning bin sizes gives 0.25° angular resolution which corresponds to a 0.7°x0.7° optimal square bin size (S/B = 39%)

Radial distribution fit at the Crab bin gives 0.33±0.06° angular resolution

Maximal S/B = 44% is seen for a 0.5°x0.5° square bin size Currently reconstructing the same Crab data a third time with only

AS+OR PMTs in the fit and no TPed shifting to see exactly what effect the shifts have – memo will be submitted after examining the no-TPed shift results and running on current reconstruction without MARS cuts

How do we put TPed shifting online? Create TPed shift files once per run number

corresponds to basically once per day – this should be plenty because largest variations on timing come from seasonal temperature changes

Use TPed shift files when creating REC files Will also create AS only reconstruction of the Crab data to see what

effect the outriggers have (not for memo)