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15-Apr-15 Muon HLT Meeting C. Diez L2 Muon Trigger Status Report: L2 seeding study B. de la Cruz, C. Diez (CIEMAT, Madrid) Muon HLT Meeting 17th April, 2009 1
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15-Apr-15 Muon HLT Meeting C. Diez L2 seeds reminder Parameters from L1 muon candidates converted into seeds for L2 muon reco pt estimated at interaction point global position ( , ) of hit at second station (MB2/ME2) firing L1 A TSOS (L2 trajectory seed) is defined at the second station with this previous info and some initial errors assigned. Great care needed, as info is not given at the same reference system At this point, L2 pattern recognition starts Track parameters from seed propagated to innermost reachable muon chamber Forward pattern reco: navigation outward Bacward pattern reco: navigation inward 2 , ptpt MB1 MB2 MB3 MB4
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15-Apr-15 Muon HLT Meeting C. Diez L2 Muon Trigger is already established but there may be still room for improvement optimizing the 2 step algorithm: Pattern Recognition in the muon system and the tuning of the L2 parameters. http://indico.cern.ch/materialDisplay.py?contribId=2&materialId=slides&confId=53973 http://indico.cern.ch/materialDisplay.py?contribId=2&materialId=slides&confId=53973 Study the L2 Seeding Vector values : Evaluate pt, at IP and second station Errors : Study L1 resolution, compared to the default errors given in the seeding Motivation for the study 3
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15-Apr-15 Muon HLT Meeting C. Diez /RelValZMM/CMSSW_3_1_0_pre3_STARTUP_30X_v1/GEN-SIM-DIGI-RAW- HLTDEBUG (9000 evts) Rerun the trigger with the configuration which is implemented for CMSSW_3_1_X Tests on L2MuonSeedGenerator 4 Change L2 seed in RecoMuon/L2MuonSeedGenerator /src/L2MuonSeedGenerator.cc and check results comparing distributions of several variables (pt, eta, phi), their pulls and resolutions.RecoMuonL2MuonSeedGenerator /srcL2MuonSeedGenerator.cc
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15-Apr-15 Muon HLT Meeting C. Diez Comparison: variables at Vtx-MB2 SimTracks (vtx)-SimHits(MB2) At simulated level: Compare simulated p t, given at the interaction point and in the second station (ZMuMu sample) 5 First approx.: shift in pt by a constant ~2 GeV (CSC), ~3 GeV (DT),
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15-Apr-15 Muon HLT Meeting C. Diez Comparison p t Vtx-MB2 SimTracks (vtx)-SimHits(MB2) 6 No statistics for Pt > 60-70GeV Check the distributions for the available “RelValSingleMuPt1000” more bremmstrahlung losses at high Pt as expected Muon pt=1000GeV Pt vtx-MB2 vs (at vtx) p t vtx-MB2 vs p t (at vtx)
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15-Apr-15 Muon HLT Meeting C. Diez Changed pt seed: Effect in L2 distribution 7 The effect is negligible (~0.3% in pt resolution) It doesn´t seem worthy to further parametrise the shift (for this sample ZMuMu at least) Some examples of pulls, Pt resolution after rerunning the L2 trigger with the new seeds FastStepHelix + Refit with default pt seed
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15-Apr-15 Muon HLT Meeting C. Diez L2 seed Errors 8 Default Errors: Are they overstimated? Check L1 resolution (L1 vs sim.) and take those values as seed error
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15-Apr-15 Muon HLT Meeting C. Diez L1 resolution 9 1.5 times smaller for CSC 2 times smaller~10 times smaller Resolution (L1-simulated) : p/pt, Error(q/pt)=0.25 /pt (1/GeV) Error( )=0.02 radError( )=0.03 rad
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15-Apr-15 Muon HLT Meeting C. Diez Effect in L2 distributions: Pulls 10 Same number of entries Sigma changes by less 0.1% Not seen any remarkable effect: Just to check see if this change actually affects at all, we removed the “refit” (right plots) The effect is a bit more visible, but still not important No ReFit
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15-Apr-15 Muon HLT Meeting C. Diez Effect in L2 distributions: Resolution 11 Comparing resolution for the “default seeds”, changed pt and pt+new error estimation : The resolution improves a bit for pt and , not for with the “pt corrected” Changing the seeds affects specially
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15-Apr-15 Muon HLT Meeting C. Diez Summary Changes in the seeding with the L2 optimizations (FastSteppingHelixPropagator (bigger extrap. steps), Refit to the L2 muon track) do not affect significantly the resolution (in pt, , ) nor the pulls. The errors studied don´t seem to be “too overestimated” For the CMSSW_3_1_X release the useful samples are only RelVal samples (ZMM, SingleMu) available, not so big statistics, relatively small pt range available Would it make sense to use other samples where there could be more muons, not back to back, etc? Ie. Min bias or pp->mu+X? 12
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