Straw and Cerenkov Timing Studies

Introduction
As many of you know I have been working on an algorithm to flag track as out of time using straw TDC information. Similarly Angel and Carlos have been working on flagging using cerenkov TDC information. The time has come to study merging the two systems to form a single timing signal for each track.

This study looks at the effects of the different timing cuts on vee signals. I also include a study of trigger timing as determined by the straws, and a study of the effects of reme cuts on SSD KS's compared to straw timing cuts.

The Sample
This sample of vees was taken from 18 full files. I selected vees of type 1, 4, 5 or 9. Each vee was require to have unambiguous timing information (cerenkov or straw) on both tracks. The criteria for unambiguous track timing are:

Straw timing: Cerenkov Timing:
  • More than one straw view contributing.
  • Greater than 50% of the views agree.
  • Greater than 50% of contributing stations agree.
  • Within a station:
    • 66% of contributing cells must agree.
    • Cell that fall into more than one cerenkov cone are not used.
    • All cells must have a corroborating ADC hit.

Out of 516,540 vees,

238,520 (46.2%) have timing information on both tracks,
211,380 (40.9%) have timing on only one track, and
  66,640 (12.9%) had no timing information.

Timing Consistency Cuts.

 

These plots show the effects of three different timing consistency cut.

The solid lines show what pass the cut and the dashed lines show the failing vees. The sum of both curves in plots 2 through 4 equal plot 1.

The same series of plots are avalible for the lambda and for SSD KS's.

These plots qualitativly show the screw-up rate for the straw tc and cer tc cuts.

The first plot show all vee that pass straw tc and fails cer tc.

(Note the signal. This indicates cer tc screw-ups!)

The second plot shows vees which pass cer tc and fail straw tc. Here we see no signal.

Lambda     SSD KS

Based on this study I intend to investigate using the cerenkov timing in cases where sufficient straw timing is not avalible. In this case the straw timing would always take precedence over cerenkov timing.

The results of this study are now avalible.

Hadronic Events out of Time.

 

These plots are fairly self-explanatory.

They show that we only have a significant KS signal in the triggering bucket (rf=0) and the buckets one removed from the trigger (abs(rf)=1).

This is consistant with the two bucket integration in the HC energy latch of the master gate.

Plots of the x opening angle for these plots are avalible.

Lambda


 
(10/16/97)

These new plots were made to investigate a hypothesis of Harry's. According to Harry, out of time hadronic events could be the result of a hadronic event following, by one rf bucket, a pair. The pair sets the trigger timing in TR2 and the hadronic event satisfys EHC latch. In this case we would expect KS in rf=1.

Timing Cuts vs. Reme

 

This study attempts to compare timing to reme for linked tracks by using SSD (type 9) vees.

Plots 1, 2, and 4 show the SSD KS mass for various straw timing conditions. The dashed lines show what would be cut out by rejecting all vees where one or both of the tracks are identifed as pair consistant by reme.

Plot 3 (lower left) show what is cut out (dashed line) by both straw tc and rf=0 cuts.

Timing cuts applied to unlinked tracks such as those used in the vee signals first vee signal study are completly orthogonal to cuts made by reme, since the 0 degree hypothosis checked by reme is done on ssd tracks.

Unfortunatly, the timing cuts have very little effect on ssd vees because their tougher vertexing requirements rule out most randomly paired tracks. Overall rf cuts are also less effective in the case of linked vees because the KS is decayed before TR2 and therfore is able to set the timing of the trigger.

On the other hand, it is clear that reme cuts, cut physics.

Questions, Comments: Jonathan Link