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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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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


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


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


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


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


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


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


L2 seed Errors

Default Errors:

  • Are theyoverstimated?

  • Check L1 resolution (L1 vs sim.) and takethosevalues as seed error

Muon HLT Meeting C. Diez


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


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


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


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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