RunII Analysis (Z-> b b, Z-> mu mu)

1
RunII Analysis (Z-gt b b, Z-gt mu mu)

• Silvia Tentindo Repond, FSU
• 12 August 2002
• FSU Group

2
Overview

• _at_ DATA - TOP data streams p11.09
• di-muons
• muonjet
• production started on the farms, 1/10 of
  data reprocessed so far. Old p10. had no
  certified global muons nor good muon alignment.
  
• _at_ MC - Z-bb new p10.15 - need p11.09
• bb-inclusive p10.08
• good for jet studies, not good for muons ,
  and jets with muons.
• Jpsi-mu mu p10.15 ( need
  p11.09 for
• higher efficiency.) right peak if global
  muons used

3
Physics channels

• Signal(s) cross
  sections
• Z ? b b (b?mu) 2 nb ( BR
  10)
• Z ? mu mu
• Jpsi ? mu mu
• Ypsilon ? mu mu
• Background
• b b inclusive
  2 ub

4
flavor creation
b bbar production at Tev

• Other contributions
• Flavor excitation
• Parton/shower fragmentation

Underlying event
b
P
P
Init state radiation
b
5
Signal(s) and Background diagrams
q
q
b
b
Z
g
b
q
q
b
mu
mu
mu
Jpsi
q
Ypsilon
Z
mu
mu
q
mu
6
Strategy

• R Signal/Background ratio 10 -3
• Improve R by
• after b tagging ( sec. Vertex, muon ) !
• - imposing kinematical cuts to data (JetE,
• JetPt, JetDphi,E3, muonPt, etc.)
• - applying energy corrections
• - selecting appropriate window in Inv Mass
  spectrum
• - applying NN techniques

7
Dimuon DATA
8
Dimuon DATA , selections and cuts

• Top sample p11.09 ( July 2002 )
• streamed di-muon events 11K so far
• -- Analysis criteria
• select quality muons (MuonId branch)
• select isolated muons ( distance from
  jets gt0.5)
• -- Invariant Mass cuts
• 2 leading muons , p_t gt 2 Gev
• 2 leading muons, Egt 8 Gev

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Dimuon DATA muons (Global) All
10
Dimuon DATA muons (Global) Good
11
Dimuon DATA Inv Mass
12
Dimuon DATA Inv Mass
13
(Dimuon) Dijet DATA
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Jets DATA , selections and cuts

• Top sample p11.09 ( July 2002)
• muonjet stream ( L1 1jet 1muon trigger)
• -- Analysis criteria
• use b tagging lepton only for now,
  extend to impact parameter and sec
  vertex next.
• select quality jets
• select quality muons (MuonId branch)
• associate muons to jets ( distance lt0.7)
  ? b tagging
• -- Invariant Mass cuts
• 2 leading jets , p_t gt15 Gev
• associated muon p_tgt 4 Gev
• two associated muons ( no p_t cuts )
  

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Cuts and selections ( cont)

• Also under study
• -- 2 leading jets back-to-back
• -- H_t
• -- unclustered energy
• Energy
  corrections
• V1.1 - January 2002
• V2.1 - May 10 2002

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Jets

• Jets distributions
• Jet Multiplicity per event eta phi Pt
  Energy MET
• Track Multiplicity per Jet . JCCA branch, R0.7
  
• Number of Good Jets gives the number of jets
  passing the standard quality cuts for jets
• JCCA EMF gt 0.05 and lt 0.95
• JCCA CHF gt 0.5
• JCCA HotF lt 10
• JCCA n90 gt 2
• Only Good Jets are used for Inv Mass
  calculations.

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Dimuon DATA - Jets
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muons in Jets

• Detected muons ( MuonId branch ) are requested
  to pass the medium quality cuts Muon Id vsn
  2.0 , Jul 2002
• N Segments 3
• Chisq_trk lt100
• A Global muon is a local muon that has been
  matched to a central track.
• Eta, phi, P and Pt distributions are given for
  the selected good muons.
• Ptrel and R(j,mu) are also calculated.
• A muon is associated to a jet if the distance
  from the jet axis is lt 0.7
• In the eta,phi plane, and if it passes the
  quality cuts.
• Multiplicities of muons per event, number of
  good muons and of muons associated to jets are
  given.

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Dimuon DATA muons(Global) Associated to jets
20
Dimuon DATA jets and muons counts
21
Energy Corrections

• Energy corrections ( Jet Energy Scale at D0 in
  RunII, D0Notes Jan 2002 and June 2002) have been
  applied to all the di jet Inv Mass
  distributions.
• The jet energy is corrected for all types of
  jets.
• In case the jet contains a muon, the energy
  correction includes the corrected muon energy and
  the neutrino energy ( muon jet en corr ).
• Inv Mass distributions, calculated for the two
  leading jets in the event, are plotted for jets
  energies uncorrected and after correction, and
  then the plots are compared.

22
Dimuon DATA Energy Corrections V2.1
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(Dimuon) Jets Invariant Mass Distributions
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Dijets DATA InvMass no en corr
25
Dijet DATA Inv Mass with en corr
26
(Dimuon) Jets DATA Inv Mass
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Conclusions

• DATA have been (re-)analyzed from the most
  recent production vsn p11.09.00, in the TOP
  di-muon streamed sample ( p10. had bad global
  muons)
• Invariant mass plots show clear evidences of
  peaks at the Jpsi, Ypsilon and eventually Z mass
• No evidences of Zs on the (Dimuon) Jet Invariant
  mass
• at this level of statistics
• Same study to be done ( re-done!) in the TOP
  mujet streamed sample.
• ? need more streamed data ( at present 10K in
  p11, were 500K in p10. 6.5 pb-1)

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Appendix

• ( Useful transparencies from my previous talks )

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Complete B Tagging studies for Zbb

• Started B tagging by using Impact parameter
• and secondary vertex information.
• Impact parameter tag
• Select jets ( two leading jets do contribute to
  Minv plots) that are tagged by Impact parameter
  at least one of the two leading jets must be imp
  par tagged.
• --- Study effects of imp par tagging on DATA, MC
  signal and MC background samples.
• ---- Combine imp par tag and Pt cuts to MInv
  distributions

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DATA bc taggings
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DATA Impact Parameter tag
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Zbb MC Impact Parameter tag
33
MC bb inclusive Impact Parameter tag
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Inv Mass Pt cuts and Mass corrections

• Pt cuts in Inv Mass ( on the two leading jets)
• 1 improve Mass resolution
• 2 - but- highly decrease the signal rate
• 1 higher is the Pt cut value on the two leading
  jets and lower is the yield of events with final
  state radiation .
• FSR events contribute to the left tail of
  the Inv Mass distribution.
• 2 need to find a method of mass correction
  that recovers jets at lower Pt in the event so
  that they could contribute to raise the Minv
  value to the correct position so to raise the
  signal rate

35
MC Zbb Inv Mass , Pt cuts
36
MC bb inclusive Inv Mass, Pt cuts
37
Inv Mass Pt cuts and Mass corrections

• QUESTION from where the right side tail comes
  in the DATA Invmass distribution?
• 1 background ??
• Study MC bb inclusive distribution ( need
  HIGH statistics, and PtGt20?? Selections )
• 2 energy corrections ??
• v2.1 en corr are over correcting DATA (
  en corr for MC are ok).
• MC Zbb distributions have NO right tail in the
  Minv distribution.
• Need to get rid of this tail too to improve Minv
  resolution.

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Old Samples

• Zbb Skimmed DATA
• Prj_root/871/b_2/kazu/data/output145xxx_a.root
• 1567 events
• Zbb MC events
• rAtpl_recocert_p11.08.00_lancs_pythia_hitv000326
  z-zbb-Plate_mb-none_170_02170135325.root
• 250 events
• bb inclusive MC events
• rAtpl_mcp10_p10.00.01_lancs_pythia_topv000305bb
  bar-incl-ptGt10.0-Plate_mb-poisson-0.5_31100351820
  01.root
• 500 events