Annual Report

1
Annual Report

• Zongru Wan
• Rutgers
• Proton/antiproton collisions at Fermilab
• CDF detector
• Taus - physics, decay and reconstruction
• Exercise tau neutrino event
• Plan tau tau event

2
Proton/antiproton collisions at Fermilab

• Start by accelerating protons
• Some protons hit target to make antiprotons
• Store antiprotons
• Use main injector to send protons and antiprotons
  into the Tevatron
• The Tevatron ramps up the beam energy

3
CDF detector

• The experiment study interesting collisions
  between protons and antiprotons
• The detector many different subsystems

• Transparent tracking in a magnetic field
• Absorb most particle with calorimeters
• Surround the outside with muon chambers
• Electronics to read out each subsystem
• Computer to record and analyze event

4
Taus - physics motivation

• Electroweak
• p p Z tt
• p p WZ (t?)(tt) /
  (jj)(tt)
• Higgs
• p p WH0 (t?)(tt) /
  (jj)(tt)
• p p H0/A0/h0 tt
• p p t t (Hb)(H-b)
  (t?b) (t?b)
• SUSY(MSSM/SUGRA)
• p p ?1?20
  (l??10)(tt?10) / (t??10)(tt?10)
• Top
• p p t t (Wb)(Wb)
  (t?b) (t?b)

5
Taus final modes of decay

• Leptonically (for example tau -gt e nu nu) BR 35,
  two neutrinos, difficult to identify
• a) Isolated lepton with relatively
  low Pt (about 30 of parent Pt).
• b) Impact parameter (ct 90µm) is
  small, hard to tell if such a
• lepton comes from tau decay.
• Hadronically, 1-prong (for example tau -gt pi nu /
  pi pi0 nu) BR 51, 3-prong (for example tau -gt
  3pi nu / 3pi pi0 nu) BR 14, 5-prong BR very
  small, one neutrino, more distinct signatures
• a) Narrow isolated jet, not an
  electron and not a muon.
• b) Low track multiplicity (expect 1
  or 3).
• c) M(visible decay products) lt
  M(tau).
• Tau reconstuction Tau decaying into hadrons
  reconstruction
• Tau id narrow, isolated jet with low track
  multiplicity

6
Taus - reconstruction

• Scan all the calorimeter for the seed tower
• Add shoulder towers
• Request narrow cluster
• Build cluster as CdfJet object
• Calculate calorimeter based kinematics
• Look for seed track pointing to the cluster
• Collect shoulder tracks around the seed
• Calculate track based kinematics (tracks in the
  10 degree cone)
• Request track based isolation of tracks in the
  10 to 30 degree annulus

7
Exercise tau neutrino event

• Real data
• Trigger missing transverse energy
  (Met)
• Time period Aug 2001 Oct 2001
• Number of events 475,903
• Integrated luminosity 1.69 pb-1
• Monte Carlo
• Generation Pythia W -gt tau nu
• Tau decay inclusively
• Number of events 10,000

8
Exercise (contd)

• Tau neutrino event filter

• Monojet

• One centrl jet with Et gt 20 GeV
• No other high Et jet with Et gt 10 GeV
• Dijet veto with opposite side Et gt 5 GeV
• Missing transverse Et gt 20 GeV

• Tau

• VertexZ lt 60 cm
• Eta lt 1. note Eta -lntan(theta/2)
• Et gt 20 GeV
• Isolation tracks in 10 to 30 degree annulus 0
• Tau is not electron, is not muon
• Tracks mass lt 2. GeV/c2

• No other high Et electron or muon

9
Exercise (contd)
1 prong
3 prong
10
Exercise (contd)

• Statistics

• Evidence of tau signal

• An excess in the one and three prong bins

11
Plan tau tau event

• Study tau tau event which could be
• Hadronic tau electron (23)
• Hadronic tau muon (23)
• Hadronic tau hadronic tau (42)