1. Tau31 Tracking Efficiency at BaBar Ian Nugent UNIVERSITY OF VICTORIA Sept 2005 Outline Introduction  Decays Efficiency Charge Asymmetry Pt Dependence cos(  ) and  Dependence Status/Summary

2. Ian NugentTau31 Tracking Efficiency at BaBar2 What is a Track? In BaBar, there are three track definition: Charged Track Any reconstructed track Good Track Loose Meets the Good Track Very Loose criteria Transverse momentum >100MeV 12 or more hits in the Drift Chamber Good Track Very Loose Meets the Charge Track criteria Momentum<10GeV Distance to closest approach to (0,0) in the xy plane <1.5cm Distance to closest approach to z=0 <10cm

3. Ian NugentTau31 Tracking Efficiency at BaBar3  Decays and the Efficiency When a  particle decays, it produces an odd number of charged tracks due to charge conservation. There are four type of events employed in this analysed: (  e  e,   )e-  (   ,   )  -  (  e  e,   )e-  (   ,   )  -  Where  represents the fourth track which may or may not be identified.

4. Ian NugentTau31 Tracking Efficiency at BaBar4 Defining Efficiency If an event is identified as a  pair decaying with two charged tracks or four charged tracks, it can be concluded that there is a missing or an extra track. The efficiency of finding a track has been defined by two methods: Where  is used as a measure of the systematics associated with the fake tracks and background from  pair decays with more than 3 tracks. Where N 3 is the number of events with a lepton tag and two charged tracks. Where N 4 is the number of events with a lepton tag and three charged tracks. Where N 5 is the number of events with a lepton tag and four charged tracks. A is the geometric acceptance of the tracking detectors.

5. Ian NugentTau31 Tracking Efficiency at BaBar5 The Correction Factor The correction factor can the be defined as a function of the Data and Monte Carlo efficiencies. Since this method is independent of the detector reconstruction, a global correction can be determined. Unfortunately, the correction factor is not surveyed in P t, cos(  ) and . Moreover, the ratio of data to MC relies on the MC to accurately model the geometric acceptance of the detector.

6. Ian NugentTau31 Tracking Efficiency at BaBar6 Efficiency as a Function of Time Rel12-18 Data The efficiency is relatively stable as a function of time. FEX BUG

7. Ian NugentTau31 Tracking Efficiency at BaBar7 Efficiency as a Function of Time Rel18 Run 3 Comparison of Data and MC with SP5 and SP8 Data GEANT4 BUG

8. Ian NugentTau31 Tracking Efficiency at BaBar8 Systematic Uncertainties The sources of the Systematic uncertainties for the Correction factor are: Channel - ½ the deviation between the  -  and  -  channel. Di-muon - ½ the deviation between the correction factor with and without the muon MC. Ghost & Loopers – ½ the deviation between  and . Non-uniformity in P t miss – ½ the maximum deviation between 3 P t miss distributions Non-uniformity in  avg – ½ the maximum deviation between 3  avg distributions Non-uniformity in  avg – ½ the maximum deviation between 3  avg distributions

9. Ian NugentTau31 Tracking Efficiency at BaBar9 Systematic Uncertainties The systematics determined from release 12.x for the muon channels.

10. Ian NugentTau31 Tracking Efficiency at BaBar10 Charge Asymmetry Because the charge of the missing track is known, the two efficiencies may be calculated for both positive and negative charged tracks. The charge asymmetry is defined as: Understanding the charge asymmetry of the detector is important at BaBar because the experiments primary focus is CP Violation, which is detected through measuring charge asymmetries.

11. Ian NugentTau31 Tracking Efficiency at BaBar11 The efficiency as a function of P t was determined with the use of a probability matrix determined from the distribution of the 4 th track in events with 4 tracks. This transformation matrix was then applied to events with 3 tracks to determine the P t distribution of the missing track. This enabled the efficiency to be binned in P t. Efficiency as a Function of P t

12. Ian NugentTau31 Tracking Efficiency at BaBar12 Efficiency as a Function of P t The utilization of a probability matrix to determine the efficiency in bins of P t was successfully demonstrated. 10% of MC and 20% of Data from Rel 12.x Run1-3 The statistical uncertainties represented here were calculated with a Toy MC program.

13. Ian NugentTau31 Tracking Efficiency at BaBar13 The Efficiency in Terms of cos(  ) and  The number of events in bins of cos(  ) and  were determined from the average value corresponding to cuts on the cos(  avg ) and  avg.

14. Ian NugentTau31 Tracking Efficiency at BaBar14 The Efficiency in Terms of  Vertical Error bars are the error on the mean, while the horizontal error bars are the RMS 10% of MC and 20% of Data from Rel 12.x Run1-3

15. Ian NugentTau31 Tracking Efficiency at BaBar15 The Efficiency in Terms of  Vertical Error bars are the error on the mean, while the horizontal error bars are the RMS 10% of MC and 20% of Data from Rel 12.x Run1-3

16. Ian NugentTau31 Tracking Efficiency at BaBar16 Status A new Tau31Tracking Efficiency skim has been developed to reduce storage as well as CPU time. Tau13 TrkEff nutples now have MC Truth information for the P t, cos(  ) and  studies and have been reduced in size to save disk space. However, request for extra variables for future detector checks are welcome. The Fortran Tau31 Tracking selection Code has been converted to C++ and merged with existing C++ Efficiency extraction Code. This reduces the disk space required and processing time. New code development is in the final stage of testing. The reproducibility issues have been satisfied (several bugs found and fixed) and the selection is now ready to be re-optimized.

17. Ian NugentTau31 Tracking Efficiency at BaBar17 Future Work P t, cos(  ) and  studies need to be Tested and verified with MC Truth information before being implemented. The source of the cos(  ) dependence of the correction factor and the charge asymmetry need to be determined. The correlations between cos(  ) and P t need to be studied. Add tau and qqbar background systematic check.

18. Ian NugentTau31 Tracking Efficiency at BaBar18 Summary The systematics of the tracking efficiency of the BaBar detector is currently limited to an accuracy of approximately 1% using the Global Tau31 Method. The results of the global tracking efficiency study can be directly applied to event, such as  decay, that contain similar topologies. For analysis which contain significantly different topologies or event with more tracks, the results of this study will be combined with the other tracking efficiency studies at BaBar, to determine an averaged correction factor, and charge asymmetry.