Muon scintillator timing studies

Introduction

Starting run 144568 (Jan 28 2002), online T0 subtraction has been implemented for the forward muon scintillator systems. That means if we study scintillator timing, we have to distinguish between data taken before and after this date. I have analyzed two samples, one from run 142626 (i.e. without online T0 subtraction), and one from run 144570 and 144571.
The T0's used online starting Jan 28 can be found here (source: Dmitri Denisov). The T0's I used for my personal offline T0 subtraction I measured from the data and can be found in the sections below.
What can be said when comparing the two samples:
We compare the spread on the A-layer pixel time of non-isolated forward ABC-tracks. The smaller this spread, the better. If we compare the "pre-run 144568" data with offline T0 subtraction applied, to the "post-run 144568" data without offline T0 subtraction applied, then we notice that "post" data without offline is slightly worse than "pre" data with offline corrections. The spread is 3.288 ns for "pre" vs. 3.577 ns for "post".
On the other hand, "post" data with offline corrections beats 'em all: a spread of only 2.3 ns can be reached.

Data from run 142626

I have analyzed 60k events from run 142626 (taken Dec 31 2001).
I plotted the time of the scintillator hits associated with a) all A-layer segments and b) all ABC-tracks. The ABC-tracks are required to have a scintillator hit in the A- and BC-layers, and the reconstruction will only make an ABC-track if there are at least two wirehits in the A-layer and at least two wirehits in the B- or in the C-layer (one in B- and one in C-layer is not enough). This is what's shown in the green histograms. In addition, the red histograms show the same information, but here both the segments and the ABC-tracks are required to be nnon-isolated (within ΔR 0.5 of a Run II 0.5 cone jet).

I made plots with and without T0 subtraction. The plots without T0 subtraction use the raw time from the Segment block. The plots with T0 subtraction use this time, but then subtract a T0 that has been derived for each octant individually from the following plots: central and forward. The plots for the forward system show a significant late "peak" in octants 3 and 4. This is due to the fact that I select forward tracks by requiring |η|>1, so some central tracks spill over into the forward ploits. The late peaks are compatible with the T0's for central octants 3 and 4.
The T0's I find for the central system are compatible with the numbers Steve Doulas obtained from the hardware logs (?). The T0's I find for the forward system seems to be identical for the North and South, i.e. octant X on the North seems to have the same T0 as octant X on the South. This is why data from the North and the South have been combined in the T0 plot for the forward system. The T0's I used are listed below.

Andrew Askew's plots

These plots separate out isolated and non-isolated muons, with respect to RunII 0.5 cone jets (JCCB jets). Data is from the express stream, all before Jan 28.

T0's used

A-layer T0's measured on 60k events from run 142626 (run was taken Dec 31 2001).

Central
OctantT0 [ns]
0 60.926 ± 0.161339
1 60.475 ± 0.171714
2 69.811 ± 0.120715
3 72.1748 ± 0.138529
4 71.7 ± 0.119499
5 68.4999 ± 0.226754
6 68.0184 ± 0.242053
7 60.254 ± 0.210183
Forward
OctantT0 [ns]
0 59.7337 ± 0.283239
1 57.7916 ± 0.126712
2 54.7731 ± 0.104566
3 53.7443 ± 0.157515
4 51.7629 ± 0.148291
5 56.5791 ± 0.0988442
6 62.0252 ± 0.118888
7 54.363 ± 0.15004

Data from runs 144570 and 144571

I analyzed ~55k events from runs 144570 and 144571. The plots show the same info as for run 142626: ABC-tracks are required to have a BC-scintillator hit and the red histograms show tracks within 0.5 of a RunII 0.5 cone jet.
The T0's for the forward system are shown to be closer to 0 now (see table below), and the T0's in the central system unmodified, when compared to previous runs.
 We can also again make the t0 subtracted plots of tracks and A-stubs. Of course some T0 subtraction has been done online already, but we can choose to apply the T0's measured offline from the plots above (and listed in tables below), or not.
These plots have been made without applying the T0's measured offline.
These plots have been made after applying the T0's measured offline.

T0's used

A-layer T0's measured on 55k events from runs 144570 and 144571.
Central
OctantT0 [ns]
0 61.2881 ± 0.337062
1 60.2775 ± 0.290371
2 69.6061 ± 0.090214
3 72.2197 ± 0.0956785
4 71.9667 ± 0.134443
5 67.425 ± 0.230882
6 68.4592 ± 0.227996
7 60.7341 ± 0.277114
North pixels
OctantT0 [ns]
0 2.53159 ± 0.116724
1 2.36548 ± 0.108203
2 2.14939 ± 0.108272
3 2.39191 ± 0.0999657
4 3.04749 ± 0.109696
5 3.03447 ± 0.108472
6 2.5292 ± 0.1045
7 3.49885 ± 0.111537
South pixels
OctantT0 [ns]
0 3.27362 ± 0.102518
1 3.38013 ± 0.0993673
2 -5.13433 ± 0.104742
3 -5.25512 ± 0.10654
4 0.689987 ± 0.106811
5 0.635043 ± 0.105752
6 1.50898 ± 0.0950992
7 1.58099 ± 0.0971563

Data from run 145101

[updated Feb 13 2002]
I analyzed ~71k events from runs 145101. The plots show the same info as for the other sections above, but I have now also imposed the "tight" requirements on the tracks in the red histograms.
The T0's for the A-phi counters (central A-layer scintillators) appear to have been changed since run 144571. They are close to 0 now, and the spread of the times within one octant is comparable to what we see in the forward system.

T0's measured offline and T0 subtracted plots

Central
OctantT0 [ns]
0 -0.0157684 ± 0.0733317
1 0.703921 ± 0.0979259
2 -0.746395 ± 0.107281
3 -0.144362 ± 0.0992987
4 0.177359 ± 0.132837
5 -0.698409 ± 0.188276
6 -0.369296 ± 0.17568
7 -0.00937825 ± 0.115377
North pixels
OctantT0 [ns]
0 1.89939 ± 0.081544
1 1.97893 ± 0.0820215
2 2.02046 ± 0.0842969
3 2.30156 ± 0.0930689
4 2.48974 ± 0.0858334
5 2.68039 ± 0.0842256
6 2.50192 ± 0.0843851
7 2.71939 ± 0.0904449
South pixels
OctantT0 [ns]
0 3.26868 ± 0.0901949
1 2.81664 ± 0.0870499
2 -2.42391 ± 0.089649
3 -2.26803 ± 0.0958574
4 0.100034 ± 0.0919722
5 -0.0405667 ± 0.0929423
6 1.48043 ± 0.0956141
7 1.3859 ± 0.0942129
My muon page
URL of this page is http://www-d0.fnal.gov/~balm/muon/scint_times
Paul Balm, last modified: Feb 13, 2002