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Search for new physics in dilepton and diphoton final states with CDF

Search for new physics in dilepton and diphoton final states with CDF. Xin Wu (University of Geneva, Switzerland) On behalf of the CDF collaboration. Muon System. Central Calorimeters. Plug Calorimeter. Solenoid. COT. Time-of-Flight. Silicon Tracker.

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Search for new physics in dilepton and diphoton final states with CDF

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  1. Search for new physics in dilepton and diphoton final states with CDF Xin Wu (University of Geneva, Switzerland) On behalf of the CDF collaboration

  2. Muon System Central Calorimeters Plug Calorimeter Solenoid COT Time-of-Flight Silicon Tracker The Tevatron and CDF (run 2) • pp collisions: Ecm = 1.96TeV • Data on tape approaching 1 fb1! • CDF detector performs well • Data taking efficiency ~90% • Analyses progress rapidly as reconstructed and calibrated data become available

  3. Search with high mass dilepton/diphoton CDF run 2 d/dM result (207 pb1, hep-ex/0412050) CDF run 1 ee result • High mass dilepton and diphoton productions are well understood in SM • Leptons (especially e and ) and photons can be cleanly identified experimentally • New physics may show up as narrow resonances or deviations (‘contact interaction terms’) NLO (DIPHOX)

  4. Models of new physics in dilepton and diphoton • Phenomenologies are well developed for dilepton and diphoton final states at hadron colliders • SUSY models • Various models with Z’ • Extra spatial dimensions (ADD and RS) • Lepton-quark compositeness • Technicolor, Leptoquarks, excited leptons, … • Searches strive to be model independent • Optimization on individual final state (signature based) • Generic cross section limit in case of negative result • Guidance from models are important • Use general features to calculate acceptance and to optimize S/N for small signals • In case of negative results, set limits on model parameters (feed back to model building)

  5. Analyses presented in this talk • Search in ee and  with 200 pb1 • Search in ee using mass and angulardistributions with 448 pb1 • Generic Z’ models with parametrization of Carena et al, PRD70:093009, 2004 • Search in  with 345 pb1 • Search in  with 190 pb1 • More exclusive searches, if time permits • Search in +met with 202 pb1 • Search in ll and lET with 307 pb1 (hot off the press!)

  6. Search in ee and  with 200 pb1 14,799 ee and 7,775  Mee150 • Selection • Isolated ee/, Et>25 Gev • Combination of triggers to ensure full efficiency • High mass data Mmm150 • Background contributions • Drell-Yan • QCD, cosmic • , tt, WW, WZ

  7. Cross section limit for Xee or  spin-2 (eg. G) • Limit is spin dependant • Acceptance depends on angular distribution of decaying particle 95%CL s*Br limit: ~ 20 fb for all spins for Mll > 600 GeV spin-0 (eg. sneutrino) spin-1 (eg. Z’) cross section limits turned into mass limits of given models

  8. (Selected) model dependents limits ~ ut Mass Limit, 95%CL (GeV/c2) • Spin-0 • R-parity violating sneutrinos • Spin-1 • Z’ with SM coupling • Z’ in GUT E6 models • Spin-2 • Gravitons in models with warped extra dimensions (Randall-Sundrum) Z’ mass limits 95%CL (in GeV/c2) RS MG mass Limits, 95%CL (GeV/c2)

  9. New search in ee of 448 pb1 • Mee still in very good agreement with SM • High mass region (M200 GeV/c2): Data: 120 Exp.: 125  11stat 30,745 ee cadidates • Use angular distribution in high mass region to increase sensitivity for new physics

  10. lab frame ll Angular distribution (cos*) Pll=0 • * : scattering angle in Collin-Soper frame • Minimize ambiguityin the incoming quark Pt Z-Axis ll • Observed angular distribution also agrees with SM

  11. Setting limits with ee of 448 pb1 • Generic Z’ search: use classification scheme proposed by Carena et al (PRD70:093009,2004) • 4 model classes: B-xL, q+xu, 10+x5, d-xL • 3 parameters : MZ’, gZ’, x • Use 2-d CLs method (used for LEPII Higgs mass limits) to set limit • Test statistics build from Poisson probabilities for SM and Z’ in (Mee, cos*)bins • Test 40k model points in 4 classes • Use acceptance matrix with same (Mee, cos*)bins • Avoid undertaking full simulation for 40k points K*LO calculation for a given model point Expectation for bin i

  12. Results fromee of 448 pb1 • Exclusion regions in (MZ’, gZ’, x) space for 4 model classes • eg. d-xu models: improve on LEPII results • Easy to obtain limit on particular models LEPII g=0.10 g=0.05 g=0.03

  13. Search in  with 345 pb1 • Selection • 2 central isolated  , ET>15 GeV • Background • SM diphoton production • Dominant at very high masses • Fakes: -jet and jet-jet • Jet fragments into hard 0

  14. Limits from  of 345 pb1 G • Virtual G exchange in warped extra dimension (RS) • 2 parameters: MG (1st graviton excitation state) and k/MPL g,q f,V Br() =2Br(ee) g,q KKn f,V RS MG mass Limits, 95%CL (GeV/c2)

  15. 0.175 0.175 Search in  with 195 pb1 • Selection • 3 final states: eh, h, hh • tau hadronic trigger used for hh • h idendification with “shrinking cone algorithm” • ET15(25) GeV for e, h (hh) • Mvis = m(vis + vis + ET)  120 GeV/c2 • control: Mvis<120 GeV/c2 shrinking cone angle1/Et

  16. 394 GeV/c2 Result of search in  with 195 pb1 • Control sample • obs. 90 vs. exp. 99.312.5 • High mass • obs. 4 vs. exp. 2.80.5 • Background • Z/g*tt • fake hfrom W+jet, multi-jet events • Cross section limit • ~ 1500 fb at high mass • Mass limit on Z’SM • MZ’ >394 GeV/c2 • ee/ (200 pb1): 620/605 • First high mass  search

  17. ~ Search inETwith 202 pb1 LSP PRD 71, 031104(R) (2005) NLSP • Selection • 2 central isolated , ET>13 GeV m(±) > 167 GeV/c2 m(0) > 93 GeV/c2 0 event observed for ET>45 Gev 0.30.1 background expected

  18. Search inll and lETwith 307 pb1 First public prestation yesterday (22/7/05) by A. Loginov, SUSY2005 • A priori selection, same as in run 1 • Tight e or  : ETl>25 GeV • Loose e or  : ETl>20 GeV (plug electron ET>15 GeV) • ET>25 GeV, ET>25 GeV • Data agrees with expectation • Run 1 (86 pb, 1.8 TeV) 2.7 excess in lET not confirmed in exact repeat of the analysis with much more data

  19. Conclusions • Searches in dilepton (e, ,) and diphoton final states with 200-400 pb-1 data from CDF run2 yields more stringent limits on production of new heavy particles • Excluded larger parameter space of many models of new physics beyond SM • Analyses continues with increasing statistics and more sophisticated search techniques • Soon 1 fb-1 on tape and 4-8 fb-1 by 2009 The Tevatron still has a chance to steal the thunder from LHC

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