Tracking and Validation

1. Tracking and Validation • What kind of feedbacks tracking can provide? • This talk: by no mean, a working package; more likely a messy collection of first ideas 15/12/04 Cern

2. Effects on tracking • The momentum measurement depends on: • Efficiencies of first and second coordinates measurements devices • Resolution of precise measurements, i.e. R-T relations • Magnetic Field • Correction of Energy losses in calorimeters • Alignment of chambers • Robustness of reconstruction program (not addressed here) The challenge is to disentangle their different effects One should take advantage of the different detector configurations (Cosmics, Toroid on/off) and try to study the different effect as soon as possible e.g. check alignment before to have to figure out how it mixes with E losses and Magnetic Field to build the Z peak 15/12/04 Cern

3. Devices functioning: checking efficiencies • 1st coordinate trigger measurement is predictable from precise measurements (MDT), so check is local and easy (segment reconstruction is enough) • One 2nd coord measurement is enough to build the track (in Muonboy at least) so prediction can be made on other 2nd coord devices and 2nd checked • 1st coordinate precise measurements • Tracks: exploiting angle-angle reconstruction, one can predict measurements in one chamber using the 2 others, and check 1st (experienced in H8) • Segments: special reconstruction with N-1 tubes, check the remaining; give tube vs impact parameter (a.f.a.I.k. not done in H8) 15/12/04 Cern

4. Devices functioning: checking efficiencies • Efficiencies can be checked what ever the detector configuration is • if one takes a position matching criteria at cm level (2nd coord.), approximate Alignment and Magnetic Field are Ok • Toroid off offers only the advantage of simpler trajectories • Some dedicated settings of the reconstruction programs are required (exclusion of device under test, or of “sick” devices); quite similar to H8; not a big deal • Time scale: for a 95% efficiency, +/-0.5% is obtained at chamber level in ~10 hours with cosmics (~1 hour at at 1033cm-2s-1 ) • With cosmics, all dead channels will be easily mapped 15/12/04 Cern

5. Devices functioning: R-T relation • Check can be local and segments reconstruction is then enough • Typical checks are those done in H8 now: residual distribution vs 1st, vs 2nd coordinate, vs radius digits/segments radius distribution… <Resid>vs radius <Resid>vs radius residual resid. vs radius digit radius H8 2004 track radius 15/12/04 Cern

6. Devices functioning: R-T relation • R-T can be checked without special setting of reconstruction • To some extent, tracks can provide consistency check between 2nd coord. dependence of RT (60/200.5 =13 cm), and 2nd coord. Measurements (cm) • It is important to do these checks with Toroid off and on, to evaluate Lorentz angle correction in R-T relation • For a residual width of 80 m, +/-1 m is reached at chamber level in, ~10 h with cosmics (~1 h at 1033cm-2s-1) • For Lorentz effect study, 2nd coordinate should be sampled; ~factor 6 in statistic if half meter scale is aimed 15/12/04 Cern

7. Checking alignment with straight tracks • “Since curvature is known for straight tracks”, they can be used to check absolute alignment delivered by optical alignment system: measured sagitta should be null Sagitta/with ali H8 2003 Sagitta/No ali Sagitta vs 1st coord • Typical feedbacks H8 analysis: checks that optical alignment compensates chambers movements, see remaining misalignments in sagitta dependencies of 1st and 2nd coordinates, .. • Up to now, H8 data have not been used to outline a procedure Observed Sagitta  Chamber Positions (work just started) 15/12/04 Cern

8. Checking alignment with cosmics • Estimates from C.Guyot, 10 k muons per chamber tower (12 parameters) needed to reach 20m: ~2-3 days (~6 h at 1033cm-2s-1) Need projective tracks PERSINT Muonboy reconstruction • Pattern recognition is not an issue with cosmics • Muonboy without algorithmic changes reconstruct projective cosmics tracks PERSINT Muonboy reconstruction • The only issue is timing: inversed time sequence and starting point (TOF correction). Not trivial but not major issue 15/12/04 Cern

9. Non projective cosmics tracks • One can envision full 3D tower reconstruction (à la Datcha UA1, 50K muons10m) Need non projective tracks (both for 3D reconstruction and rate) • Tracking is not yet adapted to this as illustrated by the extreme case of Halo event reconstruction PERSINT Muonboy reconstruction Reconstruction should be changed Pointing criteria should be relaxed; fake tracks should be controlled 15/12/04 Cern

10. Matter with straight tracks • In the 20-100 GeV range, Multiple Scattering dominates spectrometer resolution and the dead matter is highly non uniformly distributed Muonboy resolution analytical evaluation • At the low momenta of the straight tracks considered here (20 GeV), sagitta width (~600 m) is dominated by M.S. in spectro • Matter distribution within spectrometer is in principle checkable: ~1 day with cosmics (~2 h at 1033cm-2s-1 ) to trace 10% variation of X0 at 10 cm scale 15/12/04 Cern

11. Alignment with ID (Toroid on or off) • From the point of view of measurement improvement (enlarged lever arm for 1TeV muon), 200 m is the target (width due to MS in calo at 1 TeV). This is easily done • In ~1 day at 1033cm-2s-1, the muons from Z decay allow to check alignment of the ID with each physical tower at that level (~350 control points) • This is 5% of the MS width for 50 GeV ; according to a very old study (Cetraro 97) this could be translated in a control of the longitudinal and ortho-radial components of Magnetic field in Tile at 250 Gauss level • It is worth to study to which extent the alignment ID/Spectro, with or without toroid field, could be a mean to understand B and possibly Eloss in calo 15/12/04 Cern

12. Special Tracking to study alignment in overlap areas (Toroid on) Check alignment of independents sections with tracks Reconstruction should be modified • Overlap areas: • Small/Large chambers Barrel or End Cap • Barrel/End cap transition • BIS7/BIS8, BEE/End Cap • Special reconstruction is needed: measurement in one area; prediction in the other area; comparison with measurement there (NB: For barrel, tracking will directly provide the small/large chambers alignment) PERSINT Small/large sectors 15/12/04 Cern

13. Momentum measurement • At that time, (Efficiencies, R-T) will be understood and under control. • Remaining effects, Alignment, Magnetic Field and E losses will mix in any momentum measurement. • Only Alignment will have been checked before. Further checks, will be obtained comparing 3 points and angle-angle reconstructions • To disentangle Alignment, Magnetic Field and E losses effects, 2 handles (both still need detail studies with full simulations): • Momentum comparison with ID • (PID-PMS) or PID/PMS or F(PID,PMS) signed or not vs , , pT B, Eloss, Alignment effects have different dependencies on kinetic variables (p Bp; p p+E; p p/(1+a/s)) • Resonances: • Estimate (C.Guyot) 44X32 (,) bins (4 bins per tower) 2.106Z2 (1 month)=> (B)~4.10-4, (a)=15m Toy MC, 2 effects out of 3, systematics still to be studied 15/12/04 Cern

14. Conclusions • Efficiencies and R-T: • Tracking feedbacks will be H8 like (although much more effects to be studied) • No major change of reconstruction needed • Alignment: • Check alignment with straight lines tracks, with tracks in overlaps • Reconstruction changes needed • for non projective cosmics tracks (Not a pattern recognition issue) • optional underweighting of some areas w.r.t. others • Still missing but work started: Observed Sagitta->Chambers positions procedure; to be validated both in H8 and in full simulations • Dedicated studies: • check Spectrometer matter distribution through sagitta width • Magnetic Field and E loss (?) in Tile by ID/Spectro alignment • Disentangling Magnetic Field/Alignment/E losses effects: one needs detailed simulations of the potential of the comparison between ID and Spectrometer measurements and of the Z peak 15/12/04 Cern