Preliminary studies on Muon System software alignment LHCb week CERN May 29-th, June 2-nd 2006 Stefania Vecchi INFN Bologna Wander Baldini INFN Ferrara

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Muon system misalignments Muon Chambers will be positioned on the support structure within few mm from the ideal position A muon system misalignment will effect mainly the L0 trigger (Pt measurement & muon candidate selection). It might have a smoother impact in the analysis (Particle ID). With MonteCarlo simulations we can evaluate the effects of a misalignment: –Of the whole detector with respect to the others; –Of M1 respect M2-M5; –Of each station; –Of single chambers in the most critical regions in order to better define the positioning accuracies limits We use the L0muonTrigger routines to evaluate trigger performances. They allow changes in FOI or Pt cut, but not in single chamber position

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June First studies Pt calculation of each muon Candidate Changed in Tower.cpp (L0muonKernel) due to shift in M1 or M2 Study of L0muon trigger performances as a function of misalignment scale: efficiency to signal, Mbias retention, charge asymmetry ONLY effects of L0 performances on Pt calculation can be evaluated no FOI Settings: –Default FOI X/Y: M1=±5/0 M2= ± 3/0 M4= ± 3/1 M5= ±3/1 –Pile Up rejection –L0muon Trigger output rate: 125 KHz

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Data sample / DaVinci In order to use L0mAnalysis package we used RTTC data sample generated by D.Perego –Minimum Bias: events –B s  J/          events –DaVinci v14r4 –L0mAnalysis v4r4 –L0mTrigger v3r0 Run L0mTrigger introducing a shift on M1 and M2 x-coordinate (+-0.5 cm, +-1cm, +-5cm, -10cm) –Affect Pt calculation –No muon candidates losses due to FOI –Introduce charge asimmetry

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June No-Shift

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Shift M1 -0.5cm

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Pt cut and efficiency almost unchanged Charge asymmetry 20% Shift M cm

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Need higher Pt cut to Need higher Pt cut to keep 125 kHz rate keep 125 kHz rate Efficiency drops Efficiency drops Higher MB retention Higher MB retention Big Charge Big Charge asymmetry asymmetry Shift M cm

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Shift M cm Almost only one charge left

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Shift M2 +0.5cm

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Shift M cm

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Slightly different from M1 shift results (geometry) Shift M2 +5cm

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Preliminary performances summary

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Next studies Repeat the study on L0m trigger performances on DC06 ( generated aligned) data with different misaligned geometries (changing geometry reconstruction level. –In this way also effects on FOI can be taken into account. –Need to ask officially for data production? (L0 studies for TDR: 500K mbias + 30K B s ->J/  )

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Conclusions The machinery to see effects of the misalignment is working, now more quantitative studies will start (0.5 – 5.0 cm Given the big amount of combinations, for the moment we will focus mainly on M1-M2-M3 regions

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June spares

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June nominal position nominal position Real situation Simulated situation L0/reconstruction response misaligned Detector misaligned M1 M2 M3 M4 M5

Stefania Vecchi & Wander Baldini LHCb Week 29 May - 2 June Detector Granularity and readout M1M2M3M4M5 R11x2.5 GEM GEM0.6x3.1 mixed r/o 0.67x x3.6 cathode r/o 3.1x3.9 R22x5 GEM GEM1.3x6.3 mixed r/o 1.35x x7.3 cathode r/o 6.2x7.7 R34x10 cathode r/o 2.5x12.5 cathode r/o 2.7x13.5 cathode r/o 11.6x14.5 cathode r/o 12.4x15.5 cathode r/o R4 8x20 wires r/o 5x25 wires r/o 5.4x x x30.9 wires r/o Pad Dimension (cm 2 ) Chamber readout