1. EMCal Recalibration Check
Check of Debsankar’s and Dipali’s PWG Presentation on Kaon Mass Spectrum Fits
PWG presentation on May 10
Determined the EMCal particle ID function parameters based on fits to mass spectra in each momentum bin
Initial check of results shown last Monday at group meeting
My mass width results are ~30% larger than those at the PWG (slide 9)
Differences in two analyses
Different background function choices
Different mass fit regions for each momentum bin
Use of PC3 tracking cut in my analysis (re-did my analysis without PC3 cuts)
Results of checks of effects of differences done this week
Background function difference does not lead to different fit widths
PWG results are not stable with respect to size of mass fit region (slide 4) Not enough representative satellite channels for background
PC3 tracking cut leads to better Signal/Background in kaon mass region We need to think about using this cut for the Run4 analysis Effects of PC3 cuts on S/B will be tabulated in a future spreadsheet but use of PC3 cut does not explain the larger  values which I obtained
October 24, 2005
EMCal Recalibration Check

2. Slide 11 from May 10 PWG presentation
Examples of Kaon mass spectra with fits
Top half should be for K+ and K- in the 0.50 to 0.55 GeV/c momentum bin Mistake that the same K- spectrum and fit are shown twice
Corrected by Debsankar in mail to me last week See correction next slide
= 0.018
Bottom half is for the 0.90 to 0.95 GeV/c momentum bin.
Also has typo error in that right “m2n” is not the K- but it is the K+ Spectrum on the left is the K-
= 0.032
= 0.032
Note fit regions in mass2 essentially covering just larger than the peak region
October 24, 2005
EMCal Recalibration Check

3. Corrected K+ mass spectrum for 0.50 to 0.55 GeV/c
Background function = p0 + p1*exp(-p2*m2)
Note the fit region is for mass2 from 0.18 to The shape of the background at the high edge should arouse suspicion
= 0.019
October 24, 2005
EMCal Recalibration Check

4. Sensitivity of Fit Results to Fit Starting Parameters Example of 0
Sensitivity of Fit Results to Fit Starting Parameters Example of mass2 Spectrum (Using to fit range) K+ K-
Top half: Spectra and fits as shown in PWG meeting Using PWG background function
= 0.033
= 0.032
Bottom half: Same spectra but with fits as derived from different starting parameters
Gives larger  and the 2/NDF is improved
= 0.042
= 0.043
October 24, 2005
EMCal Recalibration Check

5. EMCal Recalibration Check
Checks of validity of PWG background extrapolation Using fit parameters obtained from PWG study
Plotting range 0.10 to 0.40 in mass2
K to 0.55 GeV/c
K to 0.55 GeV/c
K to 0.95 GeV/c
= 0.019
Backgrounds determined just under mass peak do not extrapolate accurately very far from mass peak region itself
= 0.018
= 0.032
October 24, 2005
EMCal Recalibration Check

6. EMCal Recalibration Check
Checks of stability of fitting using different mass2 ranges Compare PWG spectra for and my own spectra
Fitting range 0.10 to 0.40 in mass Fitting range 0.14 to 0.36 in mass2 K K K K-
= 0.024
= 0.020
= 0.021
= 0.025
= 0.024
= 0.020
= 0.021
= 0.023
Fit widths, centroids, and backgrounds are stable for two wider choices of mass2 fit region
October 24, 2005
EMCal Recalibration Check

7. EMCal Recalibration Check
Checks of stability of fitting using different mass2 ranges Compare PWG spectra for and my own spectra
Fitting range 0.10 to 0.40 in mass Fitting range 0.14 to 0.36 in mass2 K K K K-
= 0.045
= 0.045
= 0.045
= 0.045
= 0.047
= 0.044
= 0.052
= 0.047
For this momentum bin the background fit is unstable when the fit region is narrowed
October 24, 2005
EMCal Recalibration Check

8. Kaon Centroids Compared Between East and West Arms
K+ ++ field
K+ -- field
K- ++ field
K- -- field
Trends of PWG results and my results agree
The PWG results were summed over East and West Arms and over the ++ and the -- fields
For the -- field there is a distinct separation between East and West Arm centroids for both K+ and K-
For the ++ field there is less separation especially for the K-
October 24, 2005
EMCal Recalibration Check

9. Comparison of Kaon Widths with PWG results
The PWG width results are significantly lower than my results for all particle, arm, and field combinations
No big separation between East and West arm results, but there is a small separation for K+ in ++ field
For the lowest momentum bins the K- widths are slightly smaller than the K+ widths, but this difference disappears at higher momentum bins
October 24, 2005
EMCal Recalibration Check

10. Check of EMC Azimuthal Residual Centroids for Kaon m2
Azimuthal recalibration for EMCal was not completed
Centroids show consistent, systematic deviation from nominal 0.0 as momentum decreases, for all charge-field sign combinations
The same is true for the widths of residuals, next slide
Plots are for scans not using a PC3 hit requirement
October 24, 2005
EMCal Recalibration Check

11. Check of EMC Azimuthal Residual Widths for Kaon m2
Azimuthal recalibration for EMCal tracking was not done??
Widths show a significant deviation from nominal 1.0 as the momentum decreases The deviations are large enough to lead to a loss of efficiency even with a 3 tracking cut
Plots are for scans not using a PC3 hit requirement
October 24, 2005
EMCal Recalibration Check

12. Checking Effects of Requiring a PC3 Match
October 24, 2005
EMCal Recalibration Check

13. EMCal Recalibration Check
Sample kaon m2 spectrum without PC3 hit requirement Example from -- field runs
Signal and background yields in a +/- 2 wide m2 window for Gev/c momentum bin
Part
Arm
Sig
Bgrd
S/B K+ W
4502
1954
2.30 E
2096
897
2.33 K-
5013
1883
2.67
2130
645
3.30
= 0.028
= 0.026
= 0.024
= 0.025
October 24, 2005
EMCal Recalibration Check

14. Sample kaon m2 spectrum with PC3 hit requirement Same -- field runs as previous slide
Signal and background yields in a +/- 2 wide m2 window
Part
Arm
Sig
Bgrd
S/B K+ W
3881
940
4.23 E
1957
492
3.98 K-
3999
913
4.38
1831
345
5.31
= 0.027
= 0.026
Effect of PC3 cut:
Average signal loss = 14%
Average S/B gain = 1.69
= 0.024
= 0.025
October 24, 2005
EMCal Recalibration Check

15. Sample EMC azimuthal residual without PC3 hit requirement Same -- field runs as previous slides
= 1.26
c = 0.082
= 1.21
c =
= 1.14
c =
= 1.17
Fits with Gaussian + Constant Bgrnd Centroids should be nominally 0.0 and the widths should be 1.0
These are significantly not at nominal values
Constant bgrnd is at a high (~10%) level?
October 24, 2005
EMCal Recalibration Check

16. EMCal Recalibration Check
Sample EMC azimuthal residual with PC3 hit requirement Same -- field runs as previous slides
Fits with Gaussian + Constant Bgrnd Centroids similar to before but the  are slightly smaller
Constant bgrnd level is much smaller (3%) Residuals are closer to Gaussian shapes
c = 0.225
= 1.15
c = 0.096
= 1.10
c =
= 1.08
c =
= 1.14
October 24, 2005
EMCal Recalibration Check

17. EMCal Recalibration Check
Summary
Kaon particle widths derived for PWG study are too small
Larger m2 fitting region will lead to larger  values
We need to check the stability of the fitting results
We have to re-do the EMCal recalibration mass parameters
Should have separate parameterizations for East and West arms since the mass centroids are generally different between East and West
There is also some difference between the ++ and the -- fields
Other issues
Also need to fix the tracking cut parameterizations
Should investigate that use of PC3 matching PC3 was not used for Run2 because there is a loss (~15%) of yield in the single kaons and more for the pairs: Need to compare with MC Statistics not as big an issue in Run4 for the dN/dy studies
NTUPLEs with 2% of particle pro.59 CNT yields available on VUPAC system including latest recalibration software
We should check that this is no change with the newer pro.66 CNTs
October 24, 2005
EMCal Recalibration Check