Preliminary results on DT T0s in beam collisions J. Santaolalla, J. Alcaraz (+ help/suggestions from C. Battilana, C. Fouz)

MOTIVATION Check/study DT timing with muons from collisions. STRATEGY Even if statistics will be poor, try to select a rather pure sample, with minimal contamination from cosmics. Many of the ‘muons’ could be really punch- through (pions), MB1 dominated, but provided they are ‘in time’, it is OK. 12 Dec

PROCEDURE INPUT SAMPLE: –/MinimumBias/BeamCommissioning09- SD_InterestingEvents- PromptSkimCommissioning_v2/RAW-RECO SAMPLE SELECTION: –HLT bits: "HLT_MinBiasBSC_OR” | "HLT_L1Mu” | "HLT_L1MuOpen" (not critical) –At least 3 tracks in inner tracker with pt>0.5 GeV, impact parameter<0.5 cm, and at least 1 valid hit in the pixel detector (good events+well in time) FOR THE SURVIVING SAMPLE: –Compute Meantimers, tboxes, …, to check DT timing. 12 Dec

PROCEDURE We look for segments attached to StandAlone muons: –All segments having at least one hit attached to the stand-alone muon are considered. –All hits in those segments are used (wether or not they are actually included or used in fit). Some of the stand-alone muons have just one ‘station’ (stand-alone muon consider at least ‘two’, but the DT+RPC combination in one station counts as ‘two’) 12 Dec

RESULTS PHI segments (Tmean_avg = [  m]/54.5[  m/ns]) T0 used: exactly the same used in current reconstruction All hits in plot (MB1+MB2+B3+MB4). Dominated by MB1. Chamber to chamber things seem to change by <~10 ns (low statistics). Tmean points to a ns global ‘T0’ shift’ It does not seem to be a wrong vDrift, according to Tbox. Tmean – Tmean_avg (ns)Digi Time (ns) 12 Dec expected width from intrinsic resolution ~ 6-7 ns

Station by station Tmean – Tmean_avg (ns) MB1MB2 MB3MB4 12 Dec

RESULTS using t0 from segment fit. PHI segments segment->t0()~10 ns 5 ns difference with respect MeanTimer estimate Difference wire propagation correction, … ? Tmean – Tmean_avg (ns) Digi Time (ns) After ev-by-ev t0 correction 12 Dec

RESULTS using t0 from segment fit PHI segments: good correlation between meantimer and segment->t0() hit by hit Tmean – Tmean_avg T0 cor Tmean – Tmean_avg (ns) 12 Dec

RESULTS THETA segments: same shift? Digi Time (ns) Tmean – Tmean_avg (ns) 12 Dec

RESULTS using t0 from segment fit THETA segments Digi Time (ns) Tmean – Tmean_avg (ns) After ev-by-ev t0 correction 12 Dec

Conclusions (preliminary) There seems to be a global T0 shift of ns everywhere (with respect to ‘standard current’ reconstruction code). T0 determined by optimal segment fit gives a T0 shift of order 10 ns. Both Phi and Theta seem to ‘like’ this shift. Remaining (systematic) T0 shifts from chamber to chamber seem to be of order ~ 4-5 ns (systematic, i.e. on top of intrinsic statistical accuracy). T0 determined 12 Dec

TO DO Look at things in more detail (what it is shown, it was done yesterday). Understand some ‘features’: –5 ns difference between ‘meantimer shift’ and “results from t0 segment fit”. –Some strange concentrations around t=350 ns in phi timebox plot, … Try to still increase statistics as much as possible. 12 Dec