A new paper on muon detector performance ------- Discuss the paper content (bepo + roberta)

1. A new paper on muon detector performance ------- Discuss the paper content (bepo + roberta) Martellotti 24-09-2010

2. Paper content (1) • LHCb muon detector calibration and performance (after HV optimization) with collisions tracks (field on – high p muons) •  Do not treat in detail MuonID and TRIGGER • Detector setting up • optimization of the chambers working point • time alignment • Detector performance • space alignment • cluster size • efficiency of the detector

3. Content (2) Same as in previous slide with an “Historical approach” (this approach could be used in the introduction to explain the work) # A first setting up of the detector was performed in 2009 with hardware and software tools and the use of cosmic rays (ref). The settings chosen allowed to reach an adequate performance of the detectors to run the system with the first collisions with a reasonably good efficiency. # here we briefly report on the status of the detector at the time of very first collisions # we describe the subsequent improvements in the detector settings (noise, thr, HV,…) discussing the effects (…time shift…) # we describe the actions taken and procedures to improve the detector performance (new time alignment…) # we assess the “final” performance of the system with high momentum muons from collisions

4. Let’s go through possible CHAPTERS • to help discussion on • - paper content • results already established • work to be done

5. The LHCb muon system A full description of detector is needed once again ? Probably yes. In the cosmic paper we started with a very short description and we were obliged to extend…

6. Track reconstruction & Data sample • # Are the track reconstruction algorithms different for • different analysis ? Is it relevant ? • # Data sample needed for analysis to be completed may be different for different analysis: • space alignment : new analysis needed. There is an “old stripping” of min. bias with “loose” muons that should be OK. • time alignment : data already analyzed. Old HV data for equalization inside regions + new HV - TAE mode (scanning). • Do we need new analysis / new data sample for the paper? • cluster size : new analysis needed with single BC new HV data. Statistics needed? • - efficiency : we need a new high statistics sample (new HV): • Do we use downscaled minimum bias or make a selection of “non triggering” muons in triggered events ? •  Decision / Preparation of high statistics sample

7. Setting up of the detector • Status of the detector settings and performance at the beginning of LHC operation • - Briefly report on the hardware and software work done in 2009 to set up the detector for the first collisions (ref cosmic paper) • - recall the initial status of settings (and initial performance) • Do we report on the efficiency measured with the first 2009 collisions ??? • (if not, I would unify this paragraph with the next one)

8. Setting up of the detector • 2) Optimization of the chambers working point • principles - method - setting chosen : • noise level, threshold, optimized HV. • Explain the effects of changing settings (HV) on detector performance (time resolution and time alignment, cluster size, efficiency) • Are there other significant detector improvements to mention • (dead channels recovered, actions taken for GEM, …) ?

9. Setting up of the detector 3) New time alignment • # 1) equalization among channels of the same region • Collision data with old HV have been used (much higher statistics available w.r.t. cosmics in the inner regions) • # 2) optimization of the time offset per region with new HV (time-scanning data in TAE mode) • shall we give chamber time resolution ? (problem with the • distribution tails. I would avoid discussing again TDC)  • explain the “timing efficiency” in 25ns measured with TAE • events as a direct consequence of the time resolution. • report about checks done, M1, dead channels …other items? • Is further analysis needed for the paper ? On which data ? • (check with muons matched to high momentum tracks ?)

10. Detector performance 1) Space alignment - alignment done with trigger unbiased muons (from min bias events) matched to high momentum tracks - We should conclude if hardware alignment is satisfactory (yes it is) and if further (minor) improvement is possible and useful. It would be good to have an (even rough) estimate of the effect of misalignment on Trigger efficiency. # Global alignment with OT must be done. The “old” muon data sample from min bias is OK but probably we must re-run the events (tracking software modified) (*) # Alignment with MUON stand alone if possible should also be done (it is a complementary check…) (*) The present OT alignment should be good enough for us (Select field on – high momentum tracks) ?

11. Detector performance 2) Cluster size Give CS along X (or X,Y separately). Report the CS for 5 stations 4 regions (average value and CS vs angle) Use events of single BC with final HV settings Select hits associated to high momentum tracks (for other selections see Walter – ambiguities, chamber edges….) Data sample ? Statistics needed ? Explain the expected contribution from geometry… Explain the relevance of CS : show dependence on HV, stress the importance to have reasonable CS values as a check of a safe chamber working point, explain the (limited) effects of CS on Trigger

12. Detector performance 3) Efficiency Can we have efficiency vs momentum (statistics) ? If not give the efficiency measured with “high energy” muons Compare with “timing efficiency” and discuss other contributions. Try to disentangle detector efficiency and acceptance effects. Geometrical acceptance - Hermeticity - Fiducial volume… Compare with MC Data sample ?

13. Some material for discussion with some personal comment

14. Setting up of the detector Optimization of HV Time alignment

15. Multiplicities at HV_optimal.vs.2650V settings Effect of HV on cluster Show CS versus HV measured in lab? Region M1 M2 M3 M4 M5 Ratio of the average number of Pads (red) and Clusters (blue) HV_optimal/2650V for noTAE events (time centering for HV_optimal) • ~ larger DV corresponds to lower ratio (M2R1,M3R1), also Clusters change, even if less than Pads Alessia, Rob 23 apr

16. timing Giacomo 16 apr

17. Detector performance 1) Space alignment

18. Trigger efficiency - Y misalignments In the Y intercept of fitted track with plane Z=0 we see A spike of tracks with all Y pads perfectly aligned and many tracks with not aligned pads  trigger inefficiency Trigger fails for Multiple scattering Punch through Decays with large kink & Detector misalignments 1 m Stefania muon meeting 23-04-2010

19. How to spot possible trigger losses due to Y misalignment with stand alone alignment • Muon ID with ISMUON (or other equivalent algorithm) • 2) Select tracks with only 1 hit in M3 (or a cluster of hits having the same Y) • 3) Assume the projective slope IP-hitM3 (do not fit θYZ) • 4) Consider the hits “belonging” to the track and plot • ΔMi = YMi – YMiM3 (projective-extrapol from M3 to Mi) • 5) Look separately at different regions and side A-C • (eventually consider only tracks crossing M3 in the inner pads of the chambers in regions R1, R2) • # For tracks crossing the same region in Mi and M3 • Δ = 0  good alignment • Δ = ± 1 pad  physical misalignment (Mult Scatt…) • or detector misalignment • If Δ ≠ 0 for M1,M2  no L0mu trigger

20. YM2-YM3 DY = ± ½ pad When tracks change region DY = ± 1 pad Mult Scatt or misalignment R2 R3 R4 R1 Stefania

21. Y station alignment w.r.t. M3 when track change region M1 R1 R2 R3 R4 M3 Y M3 M1 M3 M1 X ± 1/4pad± 1/2pad rare frequent YM1-YM3 = R2 R3 R4 Z M3 WITH MAGNET ON TRACKS OFTEN CHANGE REGION A track in M1R3 can easily go in M3R4 rarely in M3R2 M1 X

22. +½ pad YM1-YM3 R2 R3 • DY = ± 1 pad • Mult Scatt or • misalignment -½ pad R2 R3 With uniform track distributions +1pad Misalignment (n+1-n-1) / n0 -1pad Stefania

23. 2) Cluster size

24. Walter: COSMICS - CS versus θxz Log.pad X (cm) pys.pad / log.pad 0.7 0.6 1 1 1 2.9 1 3.1 w w Wire Cath r/o 2 1 1 1 1.3 1.4 6.2 1 5.8 1 R2 w w 2.5 1 2.7 1 12 2 4 2 2 12 R3 23 4 25 5 1 5.4 1 4 8 2 R4 w w w w w M4 M2 M3 M5 M1

25. MY COMMENTS: • All regions have reasonable values but M2R4 and M3R4 • Remember that CS are measured in PAD unity •  smaller values are expected for larger pads • For wire pads we don’t expect large Cluster Size: • there is no “induction” and we never measured so high values with cosmics in Lab • Compare M2R4 M3R4 with M1M4M5-R4 that have small values as expected • M2R4 M3R4 should be much smaller than M2R3 M3R3 (having half pad size and induction) For collisions 2010 with optimized HV Giacomo reported results compatible with Walter cosmics old HV for all the stations but M2R4, M3R4 where he finds smaller values

26. COLLISIONS – no angular cut – optimized HV different definition of CS counting both X and Y adjacent hits (angular dependence neglected - is not alwais negligible) Giacomo 21-05-10

27. Giacomo

28. collisions-25ns CS versus θ (θxz woud have been better *) Giacomo * θ can be dominated by θyz that is not significant for CS

29. 3) Efficiency / acceptance

30. search window M1 to measure the efficiency of M2, M3 and M4 require the M5 hit in Dx = 5 (padx + 6. x errx) Dx = 4 padx , Dy = 2 pady Dy = 3 (pady + 4. x erry) to measure the efficiency of M5 require the M4 hit in search window M4 search window M3 search window M5 search window M2 Dx = 4 padx , Dy = 2 pady Dx = padx + 6. x errx Dx = padx + 7. x errx Dx = padx + 6. x errx Dx = padx + 6. x errx Dy = pady + 4. x erry Dy = pady + 4. x erry Dy = pady + 4. x erry Dy = pady + 5. x erry efficiency (p > 8 GeV/c) M1 M2 M3 M4 M5 ~80% of the selected Long Tracks are m’s m stations efficiency 2009 Data/MC • Distinguish between detector inefficiency and geometrical effects (acceptance at detector borders and non hermeticity) • Comparison with MC • where the detector efficiency is plugged in and well known • Acceptance effects for M1, M5 (fiducial volume...) Muon Meeting – 23/4/2010 P. de Simone 5

31. Alessia 19/05/2010 Monte Carlo