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L2 Muon Trigger Status Report: L2 seeding study

L2 Muon Trigger Status Report: L2 seeding study. B. de la Cruz , C. Diez (CIEMAT, Madrid) Muon HLT Meeting 17th April, 2009. L2 seeds reminder. Parameters from L1 muon candidates converted into seeds for L2 muon reco  pt estimated at interaction point

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L2 Muon Trigger Status Report: L2 seeding study

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  1. L2 Muon Trigger Status Report: L2 seeding study B. de la Cruz , C. Diez (CIEMAT, Madrid) Muon HLT Meeting 17th April, 2009 Muon HLT Meeting C. Diez

  2. 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 MB4 MB3  MB2 MB1 ,  pt Muon HLT Meeting C. Diez 2 24-Sep-14

  3. Motivation for the study 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 • Study the L2 Seeding • Vector values : Evaluate pt, h, f at IP and second station • Errors : Study L1 resolution, compared to the default errors given in the seeding Muon HLT Meeting C. Diez

  4. Tests on L2MuonSeedGenerator • /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 • Change L2 seed in RecoMuon/L2MuonSeedGenerator /src/L2MuonSeedGenerator.ccand check results comparing distributions of several variables (pt, eta, phi), their pulls and resolutions. Muon HLT Meeting C. Diez

  5. Comparison: variablesat Vtx-MB2 SimTracks (vtx)-SimHits(MB2) • At simulated level: Compare simulated pt, h, f given at the interaction point and in the second station (ZMuMu sample) Firstapprox.: shift in pt by a constant ~2 GeV (CSC), ~3 GeV (DT), Muon HLT Meeting C. Diez

  6. Comparison pt Vtx-MB2 SimTracks (vtx)-SimHits(MB2) pt vtx-MB2 vs pt(at vtx) • Check the distributions for the available “RelValSingleMuPt1000” • more bremmstrahlung losses at high Pt as expected No statisticsfor Pt > 60-70GeV Muon pt=1000GeV Pt vtx-MB2 vs h (at vtx) Muon HLT Meeting C. Diez

  7. Changed pt seed: Effect in L2 distribution Someexamples of pulls, Pt resolutionafterrerunningthe L2 triggerwiththe new seeds FastStepHelix + Refitwith default pt seed • 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) Muon HLT Meeting C. Diez

  8. L2 seed Errors Default Errors: • Are theyoverstimated? • Check L1 resolution (L1 vs sim.) and takethosevalues as seed error Muon HLT Meeting C. Diez

  9. L1 resolution Resolution (L1-simulated) : p/pt, L, f Error(q/pt)=0.25 /pt (1/GeV) Error(L)=0.02 rad Error(f)=0.03 rad 1.5 times smaller for CSC 2 times smaller ~10 times smaller Muon HLT Meeting C. Diez

  10. Effect in L2 distributions: Pulls No ReFit • Same number of entries • Sigma changes by less 0.1% • Notseenanyremarkableeffect: Justtocheckseeifthischangeactuallyaffects at all, we removed the “refit” (rightplots) • Theeffectis a bit more visible, butstillnotimportant Muon HLT Meeting C. Diez

  11. Effect in L2 distributions: Resolution • Comparing resolution for the “default seeds”, changed pt and pt+new error estimation : • Theresolutionimproves a bit for pt and h, notforf, withthe “pt corrected” • Changingtheseedsaffectsspeciallyh Muon HLT Meeting C. Diez

  12. 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? Muon HLT Meeting C. Diez

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