1. Anne Dabrowski Northwestern University NA48/2 Semileptonics Meeting 22 nd February 2005 Update Kmu3 Branching Ratio measurement A. Dabrowski, February 22 2005

2. 2 Particle ID Test 2 Particle ID muon strategies: 1) Muon Veto as Muon ID Check muon veto status 1 or 2 Timing association of 2ns for track between muon veto and hodoscope time 2) LKR and HAC as Muon ID ● Use the mip signal in calorimeters: ● LKR < 1.5 GeV and HAC < 5 GeV for the cluster associated to the tracks.. Requirement for signal and normalisation: ● 1 track and 1 pi0 ● Kinematic cuts using LKR and DCH Strategy: Measure Kmu3 Br normalised to pipi0 A. Dabrowski, February 22 2005

3. ● Compact 7.2 & Database pass 5 Min bias 2003 (15745,15746 and 15747) – Alignment – E-baseline correction – Bad burst – Alphas and betas – Projectivity and Blue Field ● MC Sample: – Ginsberg correction – DCH resolution correction to MC – Energy scale correction to MC (not in presented Dec 2004 numbers) Data Sample A. Dabrowski, February 22 2005

4. Simple selection wanted.... Common for Kmu3 and pipi0 ● Track Section (no extra tracks allowed): – 1 track after excluding Ghost-tracks – Hodoscope time window (-17. 20. ns) – Track quality > 0.8 CDA < 2.5, Beta, alpha corrections from database – x,y vertex (-1.8,1.8) cm, z vertex (-500,8000)cm – Blue Field correction applied ● Pi0 Selection (extra gammas allowed for both) – Energy of gamma (3, 65) GeV – Separation between gammas > 10 cm – Time difference between gammas (-5., 5.) ns – Pi0 mass cuts at 3 sigma and depends on pi0 energy – Projectivity correction – Energy scale A. Dabrowski, February 22 2005

5. Difference between Kmu3 and Pipi0 selection ● Kaon Mass (assuming pi) 0.515 GeV ● Mom (10, 40) GeV ● PT track (0.0, 0.2) GeV ● Nu mass (-0.01, 0.01) GeV 2 ● Dist between track & gammas > 10 cm ● Energy pi0 < 40 GeV ● COM pi0 < 0.24 GeV ● COM Track < 0.23 GeV ● Mass of mu pi0 < 0.445 GeV ● Particle ID for muons (2 methods used) ● Kaon Mass (0.475,0.515) GeV ● Mom (10, 50) GeV ● PT track < 0.215 ● Nu mass (-0.0025, 0.001) GeV 2 ● Distance between track & gammas > 35 cm ● PT pi0 < 0.220 ● E/P < 0.95 ● Use muon rejection only when the muon veto in used in the Kmu3 analysis. A. Dabrowski, February 22 2005

6. Summary of particle ID used: A. Dabrowski, February 22 2005 Method 1Method 2 Pipi0 E/P < 0.95 ! MUV Pipi0E/P < 0.95 Kmu3MUVKmu3(Lkr < 1.5 GeV )& (HAC < 5.0 GeV)

7. Understanding background Main Effort since December: Understanding background Method 1Method 2 Pipi0 (E/P<0.95) !MUV Kmu3 Ke3 Pipi0dk▪ Pipi0 (E/P<0.95) *Kmu3 Ke3 Kmu3 MUV Pipi0dk▪ Pipi0pi0dk ▪ Pipi0 Pipi0pi0 Kmu3 (LKr<1.5)GeV & (HAC < 5.GeV) Pipi0dk ▪ Pipi0pi0dk ▪ *Pipi0 *Pipi0pi0 pipi0g *backgrounds considered in December 2004 meeting ▪dk refers to events where the pion has decayed into a muon Backgrounds are separated into when the pion does or does not decay because the particle ID efficiencies for muons and pions are treated separately.

8. Pion ID efficiency E/P < 0.95 (common to both analysis methods) A. Dabrowski, February 22 2005 Pion ID efficiency calculated using pipi0 sample from min bias run. Kinematic cuts (as in my selection) – Muon veto requirement to reject muons – But have a tighter Kaon mass cut for this sample (0.485, 0.505 GeV). Event Timing and Fiducial cuts as in Kmu3 Br analysis

9. Muon ID efficiency E/P < 0.95 (common to both analysis methods when subtracting muon background in pipi0) A. Dabrowski, February 22 2005 Muon EOP ID efficiency calculated using K μ2 sample from min bias run; – Use only kinematics to select muons Kinematic cuts Momentum (10,40) – Min PT of 0.15 GeV – Banana PT vs P cut (Luca) – Mass ν 2 (-0.02;0.01) GeV 2 Event Timing and Fiducial cuts as in Kmu3 Br analysis Efficiency between 0.99997 and 1.0

10. Muon ID using the Muon Veto Muon ID efficiency calculated using K μ2 sample from min bias run; – check status 1 or 2 and 2 ns between hod time and muon veto time Kinematic cuts Momentum (10,40) – Min PT of 0.15 GeV – Banana PT vs P cut (Luca) – Mass ν 2 (-0.02;0.01) GeV 2 Event Timing and Fiducial cuts as in Kmu3 Br analysis Efficiency between 0.997 and 0.998 Method 1: A. Dabrowski, February 22 2005

11. Correction Factor due to pion not decaying in MC after LKR IN MC 6.4m decay volume, particle decay not simulated (LKr to MUV) Apply a correction to MC acceptance of pipi0, momentum dependent Inefficiency of 0.2% for MUV-ID taken into account Method 1: A. Dabrowski, February 22 2005 The efficiency of pion decay in pipi0 in data and MC (max z is z lkr in MC) Probability of a pion NOT decaying between LKr and MUV

12. Muon Veto ID Acceptance of signal and normalisation channel Raw Acceptance from MC Acceptance * particle ID Final acceptance (including correction factor due to decay between lkr and muon veto) kmu3 0.1052±0.0002 0.1047±0.0002 (muon veto ID) 0.1047±0.0002 No correction needed Pipi0 0.1541±0.0001 (when the pion has not decayed) 0.1531±0.0001 (E/P < 0.95) (excluding μ rejection efficiency) 0.1521±0.0001 Correction due to MC decay bin by bin Integrated value including μ -ID inefficiency overall correction 6.5‰ Method 1: A. Dabrowski, February 22 2005 Normalization Signal

13. Sources of Background to kmu3+ Source of Background Particle ID used RAW MC acceptance no particle ID Acceptance* particle ID Acceptance* Particle ID *correction Background (Accbk*Br_bk)/ (AccS*BR_signal) Pipi0dk (when pion decays before the lkr) Muon veto ID(2.05+-0.05)x10-4(2.04+-0.05)x10-4 No correction needed (1.26 ± 0.04)x10-2 Pipi0 (when pion decays after the lkr) Muon veto ID (2.84+-0.05)x10-4(2.83+-0.05)x10-4 (2.2+-0.1)x10-6 (multiply accepted events by the probability of pion decay after lkr) (1.35+0.04)x10-4 Pipi0pi0dk (when the pion decays before the lkr) Muon veto ID(2.22+-0.07)x10-4(2.21+-0.07)x10-4 No correction needed (1.11 ± 0.05)x10-3 Pipi0pi0 (when pion decays after the lkr) Muon veto ID (3.56+-0.03)x10-3 (2.52+-0.07)x10- 5 (multiply accepted events by the probability of pion decay after lkr) (1.26+-0.04)x10-4 Method 1: A. Dabrowski, February 22 2005

14. Sources of Background to pipi0+ Source of Background Particle ID used Raw AcceptanceAcc*Particle ID Need for a correction to MC decay? Background (Accbk*Br_bk)/ (AccS*BR_signal) Pipi0dk (decay before the lkr) E/P < 0.95 !MUV (2.11+0.01)x10-3(1.6+-0.1)x10-5no(1.07+-0.08)x10-4 kmu3 E/P < 0.95 !MUV (3.27+0.04)x10-3(1.3+-0.2)x10-6no(1.3+-0.1)x10-5 ke3 E/P < 0.95 !MUV (2.33±0.03)x10-3(6.7±0.4)x10-5 no (1.01±0.06)x10-4 Pipi0 (decay after lkr) E/P < 0.95 !MUV 0.1541±0.0001(4.38+-0.05)x10-4* Yes (2.32+- 0.04)x10- 6 (1.52+-0.03)x10-5 Method 1: A. Dabrowski, February 22 2005 *takes into account the decay probability for pions between the Lkr and MUV from DATA

15. Muon ID signals using the LKR and HAC Cuts chosen – LKR < 1.5 GeV and HAC < 5 GeV Muon sample using K μ2 events from min bias run. Kinematic cuts – Momentum (10,40) – Banana PT vs P cut – Mass ν 2 (-0.02;0.01) GeV 2 – Muon Veto requested Event Timing and Fiducial cuts as in Kmu3 Br analysis Method 2: A. Dabrowski, February 22 2005

16. Muon ID efficiency using the LKR and HAC Method 2: Muon ID requirement: – LKR (cluster<1.5 GeV) and HAC (cluster<5.0 GeV) – Muon ID is energy dependent with max ~0.987 – Analysis done bin by bin in momentum A. Dabrowski, February 22 2005 Recall Method 1 eff at 0.998

17. Pion mis-identification as muons using the LKR and HAC Pions can be to mis-identified as muons – Need a pion mis-identification probability, and background subtraction. Sample used for calculating the mis-identification probability – Pions from my standard pipi0 selection, with the muon Veto requirement. – Plus a tighter Kaon mass cut for this sample (0.485, 0.505 GeV). – Event Timing and Fiducial cuts as in Kmu3 Br analysis Method 2: A. Dabrowski, February 22 2005

18. Signal LKR & HAC muon ID Acceptance of signal and normalisation channel Acceptance from MC Acceptance * particle ID Final acceptance (including correction factor due to decay between lkr and hac) kmu3 0.1052±0.0002 0.1019±0.0002 (lkr & hac muon ID) 0.1019±0.0002 No correction factor needed Pipi00.1562±0.0001 No μ -ID 0.1553±0.0001 (E/P < 0.95) 0.1553±0.0001 No correction factor needed Method 2: A. Dabrowski, February 22 2005 Normalization

19. Sources of Background to kmu3+ Source of Background Particle ID used Raw MC acceptance MC acceptance* particle ID MC Acc* particle ID * decay factor Background (Accbk*Br_bk)/ (AccS*BR_signal) Pipi0dk (pion decays before the lkr) Muon ID (lkr hac) (2.05±0.05)x10-4(1.97±0.04)x10-4 No factor needed (1.24±0.03)x10-2 Pipi0 (pion decays after the lkr) Muon ID (lkr hac) (2.84±0.05)x10-4(2.75±0.05)x10-4 Yes, multiply by probability of decay (8.0±0.1)x10-7 (5.1± 0.1.)x10-5 Pipi0 (pion doesn’t decay) MuonID (lkr hac) (mis ID-prob pion as muon) (2.84±0.05)x10-4(2.5±0.1) x10-5 Yes, suppress by probability of not decaying (2.5±0.1) x10-5 (1.6±0.5)x10-3 Pipi0pi0dk (pion decays before the lr) Muon ID (lkr hac) (2.22±0.07)x10-4(2.15±0.07)x10-4 No factor needed (1.11±0.05)x10-3 Pipi0pi0 (pion doesn’t decay) MuonID (mis ID-prob pion as muon) (3.57±0.03)x10-3(2.51 ±0.03)x10-4 Yes, suppress by probability of not decaying (2.51 ±0.03)x10-4 (1.30±0.04)x10-3 Pipi0gdk (pion hast decayed before lkr) MuonID (lkr hac) (2.44± 0.05)x10-3(2.35± 0.05)x10-3No factor needed(1.94±0.01)x10-4 Method 2:

20. Sources of Background to pipi0+ Source of Background Particle ID used Raw MC Acceptance Raw Mc acceptance* particle ID Background (Accbk*Br_bk)/ (AccS*BR_signal) kmu3E/P < 0.95(3.27 +-0.04)x10-3 (3.26+-0.08)x10-3 ke3E/P < 0.95(2.34 +-0.03)x10-3(6.7+-0.4)x10-5(9.9 +-0.6)x10-5 Method 2: A. Dabrowski, February 22 2005

21. Muon Veto LKR HAC Muon Veto Comparison between methods K+ # after Background subtracted #without Background subtracted Raw # Events Data Raw Acc MC Acc*Particle ID (muon veto or E/P < 0.95) Acc * Particle ID * MC decay correction if necessary Backgrounds (Accbk*Br_bk)/ (AccS*BR_signal) pipi0 3209,3983209,815488,334 0.1542±0.000 1 0.1532±0.00010.1522±0.0001 Ke3 (1.01±0.06)x10-5 Pipi0dk (1.07+-0.07)x10-4 Kmu3 (1.3+-0.1)x10-5 Pipi0 dk after lkr (1.52+- 0.03)x10-5 pipi0 3193,7003204,410497,464 0.1562 ±0.0001 0.1553±0.0001 Kmu3 (3.26+-0.08)x10-3 Ke3 (9.9 +-0.6)x10-5 Kmu3 526,373 533,757 55,905 0.1052±0.000 2 0.1047±0.0002 Pipi0dk (1.26±0.04)x10-2 Pipi0pi0dk (1.11±0.05)x10-3 Kmu3 527,958536,110 54,623 0.1052±0.000 2 0.1018 ± 0.00020.1019 ± 0.0002 Pipi0dk (1.24+-0.03)x10-2 Pipi0 (pion doesn’t decay) (1.6+-0.5)x10-3 Pipi0pi0dk (1.11+-0.05)x10-3 Pipi0pi0 (pion doesn’t decay) (1.30+-0.04)x10-3 Pipi0gdk (1.94+-0.01)x10-04

22. ● Important steps have been taken to understand background. ● Since particle decays are not simulated in the last 6.4 m of the MC, the acceptances need to be corrected by the relevant particle decay probability ● When taking into account the particle ID efficiencies, acceptances, and background subtraction, I calculated the number of kmu3 and pipi0 events in both methods. ● Their current level of agreement is at the 3‰ for kmu3 and the 0.5 ‰ for pipi0 for the two methods. There is still some background still to be accounted for. ● Since particle ID eff are momentum dependent, next step is to extract the BR as a function of momentum. Conclusion

23. Probability of pion NOT decaying between the LKR and the HAC Method 2: A. Dabrowski, February 22 2005