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M2-M5 Absolute Efficiency

Alessia, Roberta. M2-M5 Absolute Efficiency. R.Santacesaria, February 3, 2010- Muon meeting@CERN. Efficiency calculation. Method: - MuonTrackRec standalone reconstruction using 4 stations, - Look for Clusters in the 5 th station within large tolerances

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M2-M5 Absolute Efficiency

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  1. Alessia, Roberta M2-M5 Absolute Efficiency R.Santacesaria, February 3, 2010- Muon meeting@CERN

  2. Efficiency calculation • Method: • - MuonTrackRec standalone reconstruction using 4 stations, • - Look for Clusters in the 5th station within large tolerances • around the prediction, no time cut • Assume the found cluster multiplicity distribution is due to efficiency + poissonian background • - Fit with this assumption • Data used: • - All existing beam TAE=2 events (92K) in range 63454-63990 • - All existing no-TAE events to increase statistics in some cases

  3. Reconstructed tracks-TAE events Nev=92000 Reconstructed tracks with 4 stations • Ntr-sel: • - standalone tracks confirmed by the tracker requiring agreement • within 1s between the M1 hit and the Tracker extrapolated point on M1 In addition: On M2, where more physical noise is present, also: • only one track per event (avoid clone tracks) • < 10 pad/region • no Pad ambiguity within the TS, Only combinations (1X, >1 Y) or (>1X, 1Y) are kept On M5, further cuts were needed, not enough statistics remains go to no TAE events

  4. Efficiency calculation Search window in the 5th station is ~ 6s where s isobtained by fitting the distributions of the difference between the prediction and the clusters Example of M4 x coordinate

  5. Efficiency calculation Number of clusters found within the defined windows in M4 R2 R1 R4 R3

  6. M4 k=# of clusters If k>0 SUM [(1-e) Pbgk e -Pbg/ k! + e Pbgk-1 e -Pbg/ k-1!] If k=0 SUM[ e -Pbg(1-e) ] Where SUM = Sum of the entries e = Efficiency P bg= Background probability Efficiency calculation From each histogram the efficiency e and the background probability Pbg Is extracted by fitting the following function: In this way the event correlated background is taken into account automatically since it is estimated in the vicinity of the track

  7. Efficiency calculation Number of clusters found within the defined windows in M4 R2 R1 R4 R3

  8. Efficiency calculation M4 This is efficiency in infinite time window M4R2 lower...

  9. M4R2 xy coordinates of predictions where no clusters where found c Somewhat less efficient but no clear bad regions identified

  10. Efficiency calculation M3 This is efficiency in infinite time window Lower efficiency of M3R2 is due to a particular chamber, excluding it e rises to normal values

  11. M3R2 – Chamber 16A3 A side M3R2 xy coordinates of predictions where no clusters where found c In some cases hits on wires at the right place but no cathods are hit (double readout), it that region e<~85%

  12. Efficiency calculation M2 This is efficiency in infinite time window - R1 slightly worse, probably due to leakage in the inner hole of R1. More work on the definition of the inner fiducial volume, prediction on M2 less well constrained since upstream Calo and M1

  13. Efficiency calculation M2- no TAE events Due to additional cuts on M2 low statisticslook also at no TAE events This is the total efficiency, including 25ns time window • Bad e on R1 and R2 due to bad timing - OK for R2 after having excluded the corresponding Trigger Sectors - ~ OK for R1, some residual time misalignment is still present

  14. Inefficiency in M2R1 and M2R2 is due to bad timing

  15. Efficiency calculation M5 - no TAE • Further cuts to analyze M5 in order to define a penetrating track: • Tight matching of Tracker track extrapolated to M4 • P>8GeV • - Bad e on R1 due to a broken TTC • on one ODE . Better after having • excluded it • On R4 lower e due to softer spectrum of tracks reaching R4 Need to work with a bigger sample of high momentum tracks. Tighter cuts more statistics needed Clearly This is efficiency in 25 ns

  16. Conclusions • - A first evaluation of the absolute efficiency gives results well above 99% • in almost all cases. • - A small clearly inefficient zone on M3R2 has been identified but • no explanation so far • - As far as efficiency in 25ns, eT, is well above 99% in M2R2-R4, still some residual time misalignment in M2R1 - More high momentum tracks are needed to analyze M5 • More work and more statistics to evaluate systematics - M1 efficiency to be done, big BG, different approach

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