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Preliminary results on DT T0s in beam collisions

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.

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Preliminary results on DT T0s in beam collisions

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

  2. 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.

  3. 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.

  4. 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’)

  5. RESULTS • PHI segments (Tmean_avg = 21000 [mm]/54.5[mm/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 15+-6 ns global ‘T0’ shift’ • It does not seem to be a wrong vDrift, according to Tbox. expected width from intrinsic resolution ~ 6-7 ns Tmean – Tmean_avg (ns) Digi Time (ns)

  6. Station by station MB1 MB2 Tmean – Tmean_avg (ns) Tmean – Tmean_avg (ns) MB3 MB4 Tmean – Tmean_avg (ns) Tmean – Tmean_avg (ns)

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

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

  9. RESULTS • THETA segments: same shift? Digi Time (ns) Tmean – Tmean_avg (ns)

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

  11. Conclusions (preliminary) • There seems to be a global T0 shift of 15+- 6 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. 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.

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