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Tracking session Jochen Markert, IKF Frankfurt

Tracking session Jochen Markert, IKF Frankfurt. Topics. Activities Lepton efficiency estimation Implementation of efficiency in digitizer Dependency of efficiency on the ionization of the particle track Number of wires in cluster Estimation of layer efficiency

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Tracking session Jochen Markert, IKF Frankfurt

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  1. Tracking sessionJochen Markert, IKF Frankfurt

  2. Topics • Activities • Lepton efficiency estimation • Implementation of efficiency in digitizer • Dependency of efficiency on the ionization of the particle track • Number of wires in cluster • Estimation of layer efficiency • Comparison of different tracking code versions • Reconstruction of opening angle of lepton pairs • Dependency of resolution on the ionization of the particle track • PID with MDC: energy loss

  3. Activities in MDC analysis

  4. Future tasks • First priority: Efficiency correction • Tracking for high multiplicities + CPs, needed for final DSTs of SEP05!!! • CODE STABILITY!!!!! (we lost weeks for debugging!) • Second priority: (several weeks) • Time offsets from pulser method (Khaled) • Development of “ideal tracking” • MDC part ( done by Vladimir) • Other detectors ? • Development of embedding of simulated tracks in real events • MDC part already existing • Other detectors ? • Investigation of events with very large unphysical multiplicity • How many ? Definition of reasonable numbers of tracks (SIM/DATA) • Fixing of geometry of outer MDCs • Wire angles , layer thickness (Geydar) • Wire layer offsets (Geydar + Thierry + Emilie) • Measurements on MDCIV (Thierry + Jean-Lois) • Optimization of cal2 parameters • Smoother values + analytical description (Jochen) • Retrieving parameters for out MDCs from DATA (Thierry + Emilie)

  5. Influence on the tracking efficiency • MDC efficiency (cell efficiency: gas, thresholds, noise). • MDC hardware problems (missing MBo, …). • Calibration quality • Alignment • Track finder efficiency. • Momentum reconstruction efficiency. • Matching efficiency. • Cuts efficiency (chi2 cut etc.). • Particle identification efficiency. • …

  6. Properties of wire clusters • CPR by properties of cluster size and number of wires in cluster • Tuned to get good agreement between simulation and experiment

  7. Cell efficiency in digitizer Cell efficiency not depending on energy loss of particle in digitizer

  8. Mean number of wires in cluster NOV01

  9. MDCI

  10. MDCII

  11. MDCIII

  12. MDCIV

  13. Method: Particle Layer 6 Layer 5 Layer 4 Layer 3 Layer 2 Layer 1 MDCII MDCI Detection efficiency of MDC Efficiency of Layer: A particle track has to be detected at least once per NOV01 • efficiency of wire layer better than als 89% (MIPS) Segment theoretical better than 98,4% !????? • Good agreement with laboratory measurement

  14. Layer efficiency including the wires which have been removed by tukey weights NOV02

  15. Layer efficiency from fit accepted wires NOV02 MDCI MDCII

  16. MDC Ip-blue, --red MDC II SEP05

  17. Ratio fitted segments/all segments of lepton pairs Comparison for • Exp • URQMD • PLUTO Full pair analysis and background rejection applied!

  18. Comparison of fitting track fitter for different HYDRA versions Subtitle: long story about nothing

  19. Problem description • Efficiency of track reconstruction of lepton pairs • Rumors about change in reconstruction efficiency of pairs (10%) observed by Laura between old calculation with HYDRA v7_05b and new v7_07/v7_08

  20. Method • Tracking + ideal tracking parallel (HMdcTaskSet/HMdcIdealTracking) • Filling of ntuple with HMdcTrackingEff • Efficiency calculation: • Input Pluto Sim Nov02 • Reference sample ideal segments (both inner and outer segments + Meta hits found in GEANT) • Pairs definition : inner segments cluster/fitted, no condition on outer segments, opening angle cut of 9 degree • Efficiency: found pairs / ideal pairs

  21. opening angle distribution of lepton pairs Comparison of different code versions of tracking

  22. Efficiency of lepton pairs as function of opening angle • 1ook events in simulation • No significant efficiency between the different versions

  23. Opening angle reconstruction Cut on opening angle 9 degree : Difference between GEANT angle accepted reconstructed angle accepted gives 5% more accepted pairs.

  24. Reconstruction of invariant Mass

  25. Position resolution of the track reconstrution • Resolution of the drift cells • Drift time residuals • spatial resolution : • Dependence on the primary ionization clearly visual Drift cell resolution better than 150 m design value MDCII NOV01 Data • Position resolution of the reconstruction Meets requirements

  26. Energy loss measurement with MDCs ? Contra: • MDCs measure drift times not pulse height • „Low-mass“ - concept of MDCs not optimized for dE/dx - measurement with high resolution Measurement of energy loss through width of the drift time signal („Time above Threshold“, t2-t1) as measure of deposed charge ?1 1 T. Akesson et al. Nucl. Inst. and Methods, A(474):172–187, 2001.

  27. Impact angle Normalization of signal width Drift cell Impact angle , distance from wire Drift chamber Gas amplification (HV) Track segment Mean over all cells

  28. Normalized and averaged Signal width • Protons and pions can be separated • Electrons and pions overlay • deuterons and protons overlay

  29. + 10.6 % - 9.8 % p 7.6 % d 7.2 % Resolution of signal width measurement • resolution for protons 6-9 % • resolution for pions 10-12% Data Resolution comparable with dE/dx measurement through pulse height!

  30. Correlation of signal width with dE/dx Fitted with F(dE/dxBethe-Bloch) • Correlation of signal width measurement with dE/dx property of signal shape and readout electronic1 • Good agreement for protons and pions 1L. Ratti et al., WCC 2004, Vienna, Vortrag 2004.

  31. Cathode wires Sense wire Field wire Amplification area Cathode wires The drift cell • Dimension of the drift cells 5x5 - 10x14 mm2 • Gas mixture He/i-Butan (60/40) • Simulation of the drift cells with GARFIELD - Geometry, Field, Drift MAGBOLZ - Gas properties HEED - Primary ionization

  32. Simulation: • Inhomogeneous electric Field inside the drift cell • VDrift depending on electric field Inhomogeneous distribution of VDrift inside drift cell y [cm] x [cm] Simulation with GARFIELD drift

  33. Time distance • For track reconstruction space points are needed, but MDCs measure drift times • Relation between drift time and minimal distance of the particle track from sense wire has to be known

  34. x-t- correlation • 2-dimensional drift cell model: • Simulation of the drift signals using GARFIELD • Parameterization through impac angle and minimum distance from wire • Implementation into track reconstruction and GEANT - Simulation

  35. Normalization of signal width (t2-t1) MDCII Data Nov01 • Normalization with one curve per impact angle step (5°) • MDCI/II normalized to the same value • Deviation for higher momenta

  36. Nomalization Data Nov01 Normalization of signal width • Normalization: • Impact angle (), minimal distance from wire • All chamber types normalized to common value • Normalization point at 450 MeV/c • Inner segment (MDCI/II) : • Good agreement at small momenta • Deviation at higher momenta • MDCIII/IV show different behavior as MDCI/II (statistic/geometry/working point?)

  37. Empiric formula for calculation of dE/dx resolution (MIPS): A. H. Walenta et al. Nucl. Instr. Methods, 161(45), 1979 Comparison of dE/dx resolution with other experiments • dE/dx resolution for gas mixtures with large fraction of hydrocarbon (Quencher) better as predicted

  38. The drift time measurement • The drift time measurement started by the induced signal at the sense wire • The signal gets amplified, shaped and discriminated • The TDC measures the time between the edges of the logic signal and an external signal („common stop“ (CMS))

  39. Calibration of drift times

  40. Track fitting: Track reconstruction

  41. Energy loss measurement with MDCs • Energy loss calculation with GARFIELD • Protons above 1GeV nearly minimal ionizing • Protons at 100 MeV have 4 times larger dE/dx compared to ,e,

  42. Simulation with GARFIELD

  43. y [cm] x [cm] Impact of a asymmetrical cathode voltage • Cathode voltage -1000V instead t -1750V (MDCI in NOV01) • Electric field deformed near the cathode

  44. Impact of a asymmetrical cathode voltage • Relative error of the drift time measurement compared to normal working conditions is large • Affected wire layers should nor be used in analysis

  45. Analysis of the GARFIELD Signals • „Leading“- and „trailing edge“ –times are calculated at a give threshold • Distribution of drift times of 100 tracks for a given parameter set (minimal distance, angle) are accumulated and the mean and sigma of the time measurement calculated

  46. Shape of the signals • Broad arrival time distribution near sense wire • slow electrons from the edge of the drift cell

  47. Anzahl der Cluster pro cm als Funktion der Teilchenenergie • Nimmt mit steigender Energie ab • Unterschiede zwischen Teilchenspezies ver-schwinden bei hohen Energien

  48. Anzahl der Cluster pro cm als Funktion der Gasmischung • Ändert sich mit der Zusammensetzung des Zählgases • Nimmt mit steigendem i-Butan Anteil zu

  49. Signalbreite versus Teilchenimpuls Single cell Single cell Data Nov01 • Messung einzelner Driftzellen (oberer Reihe) • Normalisierte Signalbreite für ein Segment (unten) Segment

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