D0 Calorimeter Task Force

1
Offline zero suppression

• Aim
• Understand the huge value of Missing ET at 1.5?
• Principally two runs have been studied from p11
• - 158541 1.5? run
• 157581 2.5? run
• On QCD and Bias (zero bias and minimum bias)
  events
• A method to simulate the cut at 2.5? on 1.5? has
  been developed
• ? Look at the MET resolutions for the QCD and
  Bias events

2
Determination of the sigma value

• On a file of 1.5?
• Distribution of cell energy
• by type of preamplifier
• by 4 zones of the calorimeter (-32?ietalt-15
  -15?ietalt00ltieta ? 1515ltieta?32)
• And by layer.
• Look for the maximum of the distribution,1.5?bin
  (20 of the maximum)

Value of 1.5 ?
3
Example of cuts
1.5 sigma cut at 2.5 sigma2.5 sigma
4
Met and Set at 1.5? and at 2.5? on bias events
Mean RMS 3.6 2.5 12.9 8.2
Mean RMS -0.9 2.6 -3.2 8.8
Met is 4 times more importantin run 1.5?. In run
1.5?, there is 6 times more energy than in run
2.5?.
1.5 sigma2.5 sigma
Mean RMS 1.1 3.4 1.8 10.3
Mean RMS 30.3 13.9 202.6 40.6
5
Consequences of cuts on MET and SET
Zero Bias events
QCD events
1.5 sigma cut at 2.5 sigma2.5 sigma
6
Met resolutions for QCD events
? Met value at 1.5? is understandable
7
Met/Set resolution for QCD events
? Met is varying as ?Set
8
Met resolution for Bias events
9
Met/Set resolution for Bias events
Run 1.5?
Run 2.5?
Run 1.5? cut at 2.5?
? On run 1.5?, Met is varying as ?Set
10
A lot of Negative Energy
On bias events
Run 1.5?
Run 2.5?
11
Conclusion

• The method to cut on sigma value is valid
• For a cut at 1.5? we have a MET greater than 10
  GeV on Bias events
• MET is varying as Sqrt(Set) from QCD events
• Still to look at the negative energy cells

Zero bias events
2?
2.5?
1.5?
1.7?