1. EMCal Run4 Recalibration Check Looking at K mass centroid and width
Charles F. Maguire Vanderbilt University

2. Procedure for Mass Checking
Using Stripe 2 CNTs as input processed with recalibrator
Files divided into four groups (only valid runs considered)
First half of ++ runs
Second half of ++ runs
First half of -- runs
Second half of -- runs
Analyze the East and West Arms separately
East Arm has about half the yield of the West Arm
Checks done for hot and dead towers, dual hit towers, DC ghosts
Use 3 track matching with nominal 0.0 centroid (needs iteration)
Mass spectrum fitting (will also compare with May PWG results)
Mass-squared spectrum is fitted from 0.1 to 0.4 [GeV/c2]2
Fit function is 3 parameter background + Gaussian for the Kaon
Background function is c1 + c2/chan2 + c3/chan4 {corrected version}
Plan to investigate alternative background function for systematic check
Use fourteen momentum bins from to GeV Lowest momentum bin has barely visible mass K+ peak
October 17, 2005
EMCal Recalibration Check

3. Mass Centroid Dependence: sample fitsK+ K+ K+ K+
0.325
0.525 K K K K K+ K+ K+ K+
0.975
0.825 K K K K
October 17, 2005
EMCal Recalibration Check

4. Mass Centroid Dependence:++ Field Runs
West Arm
East Arm
Clear charge sign dependence Some East-West dependence
October 17, 2005
EMCal Recalibration Check

5. Mass Centroid Dependence:-- Field Runs
West Arm
East Arm
Clear charge sign dependence More East-West dependence
October 17, 2005
EMCal Recalibration Check

6. Mass Centroid Dependence: ++ to -- transition
West Arm
East Arm
No large transition effect
October 17, 2005
EMCal Recalibration Check

7. Mass Centroid Dependence: compare to PWG
West Arm
East Arm
May 10 PWG result similar
October 17, 2005
EMCal Recalibration Check

8. Mass Width Dependence: ++ Field
West Arm
East Arm
Distinct charge dependence
October 17, 2005
EMCal Recalibration Check

9. Mass Width Dependence: -- Field
West Arm
East Arm
Distinct charge dependence
October 17, 2005
EMCal Recalibration Check

10. Mass Width Dependence: ++ to -- transition
West Arm
East Arm
October 17, 2005
EMCal Recalibration Check

11. Mass Width Dependence: compare to PWG
West Arm
East Arm
PWG  are lower
Need to check fitting function dependence
October 17, 2005
EMCal Recalibration Check

12. EMCal Recalibration Check
Summary
Kaon Mass Centroid
Clear difference between K+ and K- at lower half of momentum range
Difference is almost the same whether in the ++ or the -- field Implies this is not a detector or software artifact due to trajectory bend
Is there any physics explanation for the K+ and K- difference? Should look at the proton and the anti-proton masses
Momentum dependence similar to that observed in May 10 PWG presentation by Dipali and Debsankar
There is some East-West dependence, especially in -- field runs
Kaon Mass Width
Linear rise of width for momentum greater than 0.5 GeV/c
Widths below 0.5 GeV/c are approximately constant or rising
The K+ widths at the lowest momenta are a little larger than the K- widths
The widths derived in this study are systematically larger than the widths shown in the PWG presentation: need to check functional dependencies
October 17, 2005
EMCal Recalibration Check