1. 1 Annual Report Zongru Wan Rutgers  Proton/antiproton collisions at Fermilab  CDF detector  Tau’s - physics, decay and reconstruction  Exercise: tau neutrino event  Plan: tau tau event

2. 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. 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. 4 Tau’s - physics motivation  Electroweak p p Z ττ p p WZ (τυ)(ττ) / (jj)(ττ)  Higgs p p WH 0 (τυ)(ττ) / (jj)(ττ) p p H 0 /A 0 /h 0 ττ p p t t (H + b)(H - b) (τυb) (τυb)  SUSY(MSSM/SUGRA) p p χ 1 ± χ 2 0 (lυχ 1 0 )(ττχ 1 0 ) / (τυχ 1 0 )(ττχ 1 0 )  Top p p t t (W + b)(W ¯ b) (τυb) (τυb)

5. 5 Tau’s – final modes of decay  Leptonically (for example tau -> 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 (cτ = 90μm) is small, hard to tell if such a lepton comes from tau decay.  Hadronically, 1-prong (for example tau -> pi nu / pi pi0 nu) BR 51%, 3- prong (for example tau -> 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) < M(tau).  Tau reconstuction = Tau decaying into hadrons reconstruction  Tau id = narrow, isolated jet with low track multiplicity

6. 6 Tau’s - 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. 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 -> tau nu Tau decay: inclusively Number of events: 10,000

8. 8 Exercise (cont’d)  |VertexZ| < 60 cm  |Eta| < 1. note: Eta = -ln[tan(theta/2)]  Et > 20 GeV  Isolation tracks in 10 to 30 degree annulus = 0  Tau is not electron, is not muon  Tracks’ mass < 2. GeV/c 2  Tau neutrino event filter  Monojet  One centrl jet with Et > 20 GeV  No other high Et jet with Et > 10 GeV  Dijet veto with opposite side Et > 5 GeV  Missing transverse Et > 20 GeV  Tau  No other high Et electron or muon

9. 9 Exercise (cont’d) 1 prong3 prong

10. 10 Exercise (cont’d) An excess in the one and three prong bins  Evidence of tau signal Real dataW -> tau nu MC Initial events475,90310,000 Tau reconstruction63,1952,842 Monojet2,145497 Tau filter101281  Statistics

11. 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%)