Z  BF using  hadronic events Silke Duensing Aug 8th, 2003

 Decay and Identification hadronic  decays No L1 track trigger  Use leptons  Choose for muon  type  type

Z     hadronic 

hadronic  Reconstruction Understanding the Tau –Reconstruction

hadronic  Reconstruction Understanding the Tau oTrack matching Tracks, pT > 1.5 in 0.5 cone 2nd, 3rd track: consider invariant mass + charge 3 prong tracking efficiency: unknown 1 prong as 3 prong: pickup tracks 3 prong as 1 prong: inefficiency

hadronic  Selection (  -type)

Signal sample and Trigger Select  had candidates: Clean, high pT muon Muon is isolated –Cut on max(E T Halo +  p T trk in 0.5) –Used cut is used in optimization of cut Require  with uncorrected ET > 10 GeV MU_TAU10_L2M0 Trigger contains muon terms at L1 and L2 L1: + 1 trigger tower (0.2x0.2 in  ) above 5 GeV CJT  -specific term at L3 a L3 track > 5 GeV Require a match of tau to trigger objects

hadronic  L  L  rigger Understanding the Tau –Reconstruction –Separation into Types –Selection using Square Cuts –Trigger Efficiency Not many taus in data Thus use QCD jets that are tau-like Checked “box”-result with profile weighting

Towards the Z  had cross-section Muon+Tau Efficiencies Isolation Trigger Efficiency Background –From: QCD W  Z  ->opposite sign! WW tt same chg = opp chg small, from MC Reject w. cuts

Backgrounds (I) –From: QCD W  Z  ->opposite sign! WW tt same chg = opp chg Reject w. cuts Additional (  > 0.5) loose mu (in fid region) Isolated track w. pT > 15 (in non-fid region) Use Z  in data  to get # of remaining events in signal

Background (II) –From: QCD W  Z  ->opposite sign! WW tt same chg = opp chg small, from MC Reject w. cuts Use MC muon, account for data efficiencies, use tau + electron efficiencies

Backgrounds (III) –From: QCD W  Z  ->opposite sign! WW tt same chg = opp chg small, from MC Reject w. cuts

The candidates in the  case …are expected to be back-to back …and have an invariant mass of the muon and tau 10<m<60 GeV

Putting the pieces together

Systematics on selection Three sources of systemtatics in selection: –JES when cut on ET/pT –Tracking efficiency for track isolation –MC modeling for shape cut JES: vary E by 10% Tracking isolation –Compare Z  MC and data Shape cuts: –Look at os – ss events, –Correct with CM efficiency  constant?

Systematic check: electrons as taus For main seletion: Take electron factor from MC Check with cross section Including electron cut  : fractor  1.3

Isolated muon Muon is isolated –Muons from Z  are like muons from Z  –Signal: use Z mm –Background: events with low MET –Used cut is used in optimized

hadronic  L  rigger Understanding the Tau –Reconstruction –Separation into Types –Selection using Square Cuts –Trigger Efficiency Not many taus in data Thus use QCD jets that are tau-like