1. 07/16/2002 p. 1 Muon Fake RatesPetra Merkel Muon Fake Rates Concept: determine rate of fake muons due to pion/kaon punch-through (PT) muons out of pion/kaon decay-in-flight (DIF) Need source of identified high-pt pions/kaons: reconstruct D0 K  reconstruct K s  Method in Run1: use inclusive photon sample, look for isolated high-pt tracks therein compute probability for PT per track from hadronic interaction lengths compute probability for DIF per track from c   / c  K sum over all high-pt tracks in sample see: Thesis by J.Berryhill, PRD of note 5569; no dedicated note found

2. 07/16/2002 p. 2 Muon Fake RatesPetra Merkel K s Selection Use B_CHARM dataset: L1: (2 XFT tracks, opp. charge,  5.5) or (7 tracks w/ Pt > 2) L2: 2 SVT tracks,  2 2, 100  m < |d 0 | < 1 mm L3: 2 SVX-COT hybrid tracks, Pt > 2, |  | < 1.2, 120  m < |d 0 | < 1 mm, opp. charge, |  Z 0 | 200  m,  Pt > 5.5 Offline selection: Track cuts: N ax > 24, N st > 24, |Z 0 | 2 Track pairs: opp. charge, |  Z| 5 Secondary vertex fit: CTVMFT algorithm, x2 1 cm, d 0 (K s ) < 0.3 mm (SVX) / d 0 (K s ) < 0.3 cm (COT)

3. 07/16/2002 p. 3 Muon Fake RatesPetra Merkel K s Peak – BCHARM sample M  [GeV] Peak: 0.46 < M  < 0.53 SB: 0.425 < M  < 0.46 0.53 < M  < 0.565

4. 07/16/2002 p. 4 Muon Fake RatesPetra Merkel Pions – Kinematics eta Pt [GeV] D 0 (SVX) D 0 (COT) D 0 (SVX) : both legs have silicon hits D 0 (COT) : only one leg or none have silicon hits peak sideband

5. 07/16/2002 p. 5 Muon Fake RatesPetra Merkel Muon Cuts Use same cuts as in  (W  ) analysis: Tracking: N ax > 24, N st > 24 Calorimeter, isolation: E(R<0.4) corrected for track < 2 Calorimeter, MIP: E em < max(2, 2+0.0115 (Pt – 100)) E had < max(6, 6+0.028 (Pt – 100)) Matching: |  x| CMU < 3 cm, |  x| CMP < 6 cm, (no cut for CMX)

6. 07/16/2002 p. 6 Muon Fake RatesPetra Merkel Fake Rate – BCHARM sample K s in peak: 16,316  (Pt>5): 17,724 [%]  is  : 117 = 0.66 +- 0.06 Muon fake rate from  is CMU  : 90 = 0.51 +- 0.05 PT and DIF [%]:  is CMP  : 31 = 0.17 +- 0.03  is CMUP  : 20 = 0.11 +- 0.03 peak – SB:  is CMX  : 17 = 0.10 +- 0.02 all  : 0.65 +- 0.06 CMU  : 0.52 +- 0.06 Events in SB: 1,032 CMP  : 0.16 +- 0.03  (Pt>5): 1,179 [%] CMUP  : 0.11 +- 0.03  is  : 9 = 0.76 +- 0.25 CMX  : 0.09 +- 0.02  is CMU  : 4 = 0.34 +- 0.17  is CMP  : 5 = 0.42 +- 0.19  is CMUP  : 2 = 0.17 +- 0.12  is CMX  : 2 = 0.17 +- 0.12

7. 07/16/2002 p. 7 Muon Fake RatesPetra Merkel Fake Rate BCHARM ALL PHOTON DIPHOTON ELE8x20 ELENOV peak sideband

8. 07/16/2002 p. 8 Muon Fake RatesPetra Merkel Fake Rate – diff. distr. CMU CMP CMUP eta Pt [GeV] Only Ks peak fake rates shown, not SB subtracted yet…

9. 07/16/2002 p. 9 Muon Fake RatesPetra Merkel ELECTRON sample M  [GeV] d 0 [cm] SVX COT

10. 07/16/2002 p. 10 Muon Fake RatesPetra Merkel Physics Bias? Observe systematic difference between different datasets: BCHARM, DIPHOTON: high fake rates PHOTON, ELECTRON: low fake rates BCHARM, DIPHOTON are muon enriched Hypothesis: in muon enriched samples the pion track gets accidentally matched to the stub from a real muon nearby Check: loosen / tighten |  x| cut on CMU, CMP : fake rate / (check it both for the BCHARM and the electron sample)

11. 07/16/2002 p. 11 Muon Fake RatesPetra Merkel Physics Bias! Difference between datasets is good handle on systematic uncertainty of this measurement Tendency also seen in electron dataset…but within statistical error… BCHARM ELECTRONS |x|<15 cm |x| < 3 / 6 cm |x| < 1 cm

12. 07/16/2002 p. 12 Muon Fake RatesPetra Merkel Comparison to Run1 Numbers In Run1 (photon-lepton analysis, J.Berryhill): 1.87 +- 0.99 PT background events 1.08 +- 1.20 DIF background events 2.95 +- 2.19 background events DIF+PT 398 high-Pt tracks in inclusive photon sample Using (0.65 +- 0.06)% fake rate for Run2 Combine with 398 tracks: 2.6 +- 0.2 background events Main systematic uncertainty in Run1 was pion/kaon fraction, probably much too pessimistic…

13. 07/16/2002 p. 13 Muon Fake RatesPetra Merkel ToDo Still to do for K s : go to lower Pt (2 instead of 5 GeV) to see Pt dependence better plot peak-SB fake rate vs. eta and Pt Do the same for D0 in order to get to higher Pt and to get kaons: the signal is there, needs clean-up: