Muon fake rates: a systematical approach

Muon fake rates:a systematicalapproach CMSSWPD meeting - Luca Perrozzi

Framework and data sample • CMSSW_2_2_3 using PATtuples • B decays yielding muons (including DIF) • /QCD_BCtoMu_PT30to50/Summer08_IDEAL_v11_redigi_v1/GEN-SIM-RECO • 30GeV < Pt(hat) < 50GeV • s = 91.77 mb • Filter efficiency = 0.0061 • Generated Muons (Pt>5GeV, |h|<2.5) ≥ 1 • No trigger requirements • 600k events used so far (L= 1027 nb-1) • PAT (or TMLastStationOptimizedLowPtTight) muons CMSSWPD meeting - Luca Perrozzi

Checking fake rates on data K0s→p+p- case Reco K0s Pi tracks from K0s Background Pi tracks from K0s Signal Sig - Bkg Reco Mu Pi (from K0s) fake rate (as function of Pt, Eta, Phi,dxy, decay length) Pi Rate DR<0.01 DPt<0.01 DR<0.01 DPt<0.01 Mu/Pi Mu Rate Mu associated to Pi track from K0s Signal Mu associated to Pi track from K0s Background Sig - Bkg CMSSWPD meeting - Luca Perrozzi

Reco m-p(from Ks)association cuts m m DPt/Pt<0.01 DPt/Pt vs |DR| m |DR|<0.01 CMSSWPD meeting - Luca Perrozzi

K0sp+p- case V0 module output CMSSWPD meeting - Luca Perrozzi

Phi distributions for p and m - Stage I Pions • Select Pi tracks from K0s mass signal and background region, then look for associated m Black: Signal region Violet: Bkg region Log scale! Muons associated to Pions Black: Signal region Violet: Bkg region CMSSWPD meeting - Luca Perrozzi

Pi from K0s fake rate vs. Phi - Stage II phi distribution after Sig-Bkg • Subtract sidebands (Sig-Bkg) for m and p, then obtain fake rate as ratio m/p Black: Pions Red: Muons Log scale! Fake rate as a function of phi CMSSWPD meeting - Luca Perrozzi

K0sp+p-fake rate summary K0s mass mean (MK): 0.498079 GeV K0s mass sigma (sK): 0.006585 GeV Signal region: |M-MK|<1.4 sK Background region: 2.8 sK <|M-MK|< 4.2 sK NB: large muon fraction in sidebands requires larger Bkg sidebands to reduce statistical errors !!! CMSSWPD meeting - Luca Perrozzi

L0pp- case V0 module output CMSSWPD meeting - Luca Perrozzi

L0pp-fake rate summary (ponly) L0s mass mean (ML): 1.115850 GeV L0s mass sigma (sL): 0.002550 GeV Signal region: |M-ML|<1.4 sL Background region: 2.8 sL <|M-ML|< 4.2 sL NB: large muon fraction in sidebands requires larger Bkg sidebands to reduce statistical errors !!! CMSSWPD meeting - Luca Perrozzi

fK+K- case Made “by hand” CMSSWPD meeting - Luca Perrozzi

fK+K- fake rate summary L0s mass mean (ML): 1.115850 GeV L0s mass sigma (sL): 0.002550 GeV Signal region: |M-ML|<1.4 sL Background region: 2.8 sL <|M-ML|< 4.2 sL NB: large muon fraction in sidebands requires larger Bkg sidebands to reduce statistical errors !!! CMSSWPD meeting - Luca Perrozzi

Updates • TMLastStationOptimizedLowPtTight muons used • Background sidebands expanded • Nuclear interactions examples with GenPKs • 1,2,3 prong vertexes • New resonances added in V0Producer • New tracking algorithm example CMSSWPD meeting - Luca Perrozzi

Muon selectors efficiencies & purity CMSSWPD meeting - Luca Perrozzi

PAT vs LastStation muons (I) • Select Pi tracks from K0s mass signal and background region, then look for associated m Muons associated to Pions Muons associated to Pions PAT muons Last station muons Black: Signal region Violet: Bkg region Black: Signal region Violet: Bkg region Pt distribution after Sig-Bkg Pt distribution after Sig-Bkg Black: Pions Red: Muons Black: Pions Red: Muons Last station muons PAT muons CMSSWPD meeting - Luca Perrozzi

PAT vs LastStation muons (II) Using LastStation muons statistics decreases dramatically! (factor ~5) Fake rate as a function of Pt Fake rate as a function of Pt Last station muons PAT muons impact parameter distribution doesn’t change significantly Muons associated to Pions Muons associated to Pions PAT muons Last station muons Black: Signal region Violet: Bkg region Black: Signal region Violet: Bkg region CMSSWPD meeting - Luca Perrozzi

PAT vs LastStation muons (III) Using LastStation muons fake rate decreases a factor ~5 !!! Fake rate as a function of phi Fake rate as a function of phi PRELIMINARY CMSSWPD meeting - Luca Perrozzi

K0sp+p- case New FIT! • Sum of 2 gaussian fits perfectly mass • distribution shape • Need to redefine s Old FIT! CMSSWPD meeting - Luca Perrozzi

Significance F = Ns + Nb – kNc If NC = kNB S+B C CMSSWPD meeting - Luca Perrozzi

Background sidebands extension • If we try to plot mass distributions for all Ks (black) and only for those with at least one pi-mu association (red) we obtain top plot. • If we divide histograms (red/black) we see that oustide peak region ratio rises linearly so we can extend our background sidebands. • Fitting top red histogram no clear changes in mass peak’s mean and sigma are noticed (also fixing one of the two parameters) with respect to black histo CMSSWPD meeting - Luca Perrozzi

Background sidebands extension Bkg/Sig = 5 Bkg/Sig = 1 CMSSWPD meeting - Luca Perrozzi

Nuclear Interacions • p,p±,K± production points xy view zR view R distribution d0 distribution NO B field propagation! CMSSWPD meeting - Luca Perrozzi

Nuclear Interacions (at least 2 prong) • (at least) 2-prong p,p±,K± vertexes selected xy view zR view R distribution d0 distribution NO B field propagation! CMSSWPD meeting - Luca Perrozzi

Nuclear Interacions (at least 3 prong) • (at least) 3-prong p,p±,K± vertexes selected xy view zR view R distribution d0 distribution NO B field propagation! CMSSWPD meeting - Luca Perrozzi

Tracker layers’ radii CMSSWPD meeting - Luca Perrozzi

D0 from V0Producer CMSSWPD meeting - Luca Perrozzi

Phi from V0Producer CMSSWPD meeting - Luca Perrozzi

J/Psi from V0Producer CMSSWPD meeting - Luca Perrozzi

Last CMS WEEK announcement • Available (but non standard) in 2_2_X • NOT available in 2_2_X CMSSWPD meeting - Luca Perrozzi

Old/new tracking comparison • Test on 500 events with V0Producer (K0s reconstruction) • The difference in production radius distribution is impressive! • Needs to be run on RAW • 3-4 SECONDS PER EVENT… Red – old tracking algorithm Black - new tracking algorithm CMSSWPD meeting - Luca Perrozzi

BACKUPSLIDES CMSSWPD meeting - Luca Perrozzi

Reco m-p/p(from L0)association cuts • DPt/Pt distribution with/without DR cut m L0 or protons Black: without cut Red: with cut CMSSWPD meeting - Luca Perrozzi

CDF analysis highlights • Motivations • Large compared to NLO QCD expectation when measured with muons PRD 69, 072004 (2004) • Time-integrated mixing probability c larger than e+e- resultPRD 69, 012002 (2004) • Low-mass dilepton spectrum inconsistent with QCD expectations from heavy flavor PRD 72, 072002 (2005) • Results • There is an unexpected sample of muons which do not give hits in the first two silicon layers (r<2.5 cm) and which have a very large impact parameter (IP); hereafter called “ghost” muons (fanciful term). • The size of the ghost sample is about the same as the bb sample. • Around ghost muons, additional ones are found with similar characteristics • Known sources • Ghost excess CMSSWPD meeting - Luca Perrozzi

Analysis Plan (I) • Check track reconstruction efficiency for tracks with large Impact Parameter (IP) • MC study of track reconstruction efficiency vs IP, vs radius of production point • Validation on data using tracks from Ks decay • Choose most suitable tracking algorithm • Check resolution in IP determination • Measure in data with dimuon resonances • Check IP, Pt distribution from most relevant sources of reconstructed muons of choice (GM?) • Punch through (PT) • Decays in flight • Semileptonic B,D decays }Data control samples • K0s→p+p- • →K+K- Lpp • D0 →p+K- CMSSWPD meeting - Luca Perrozzi

Analysis Plan (II) • Study secondary tracks from nuclear interactions and their contributions to IP tails • Compute expected background rate in well-defined IP/Pt region • Jump on data! • Technical points: • there is no impact parameter for genPs • We used linear extrapolation back to primary vertex • GenPs are reconstructed before GEANT detector simulation • We used K. Ulmer private code to recover DIF and nuclear interactions CMSSWPD meeting - Luca Perrozzi

Muon fake rates: a systematical approach