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Searches for Resonances in dilepton final states

This talk discusses the searches for resonances in dilepton final states at PANIC 2008 conference. Topics include lepton flavor violating models, SUSY, and maximal flavor violation models. Results from the CDF Collaboration at the Tevatron Collider are presented.

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Searches for Resonances in dilepton final states

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  1. Searches for Resonances in dilepton final states PANIC 20089th-14th November 2008, Eilat, ISRAELA. Canepa for the CDF Collaboration

  2. In this talk ! 2003 2005 2008 Outline • Lepton flavor conserving models • New U’(1), Extra-dimensions • Lepton flavor violating models • SUSY • Maximal Flavor Violation models Peak luminosity, 321 1030 cm-2s-1 Tevatron Collider The current energy frontier ! • Proton-antiproton collider • s = 1.96 TeV at t = 396 ns A. Canepa

  3. Muon chambers Central HAD Calorimeter Central EM Calorimeter Central Outer Tracker Silicon Tracker Central Shower Max (CES) CDF at Tevatron Data for the searches collected with single muon (electron) trigger at pT (ET) > 18 GeV A. Canepa

  4. Used for normalization to data Z’ (I) New U’(1) spontaneously broken  new massive Z’ boson coupling to SM fields 2.3 fb-1 Optimized calibration of COT pT correction using E/p pT scale from Z Events with two muons pT > 30 GeV • Main backgrounds from • EWK processes • Cosmic rays • Kaons and jet misID as leptons Di-mass resolution constant in m-1 Data statistically consistent with the SM expectations (p-value 6.6%) A. Canepa

  5. Z’ (II) Likelihood fitter  95% C.L. upper limit on the number of signal events • 35 bins in search region m-1 < 10 TeV-1 • Resonant pole width  = 2.8%  M • Assume no interference between SM Z/* and Z’ SM like Z’ m > 1.03 TeV/c2 at 95% C.L A. Canepa

  6. Z’ee • Main backgrounds from • EWK processes • jet misID as leptons Energy scale from Z Events with two electrons ET > 25 GeV 2.5 fb-1 SM like Z’ m > 966 TeV/c2 at 95% C.L 2.5 significant excess in [228; 250] GeV A. Canepa

  7. G RS model of warped extra-dimensions gravitons propagating in the bulk KK tower of excited modes couple to SM fields • Scale of the model • ~ MPl e-kR k = curvature of space-time Coupling ~ 1/ Graviton @ k/MPl = 0.1 m > 850 GeV/c2 at 95% C.L A. Canepa

  8.  sneutrino  SUperSYmmetry • New boson (fermion) partner for each SM fermion (boson) Lepton (or baryon) number violation allowed in the theory sneutrino @ 2BR = 0.01 m > 810 GeV/c2 at 95% C.L “Single” coupling dominance A. Canepa

  9. sneutrino e, , e (I) • To probe lepton flavor violation decay, select events with taus decaying hadronically! New algorithm for ID of energetic hadronic taus Calibration of CES detector to improve resolution of tau visible momentum Response of hadronic calorimeter tuned to data A. Canepa

  10. sneutrino e, , e (II) 1.0 fb-1 Events with one muon (electron) pT (ET) > 20 GeV and one hadronic tau Visible ET > 25 GeV • Major backgrounds • EWK and W+jet • jets and  misID as leptons Background in signal region extrapolated from low mass region e e  A. Canepa

  11. sneutrino e, , e (III) Data statistically consistent with the SM expectations in all search channels Mass cut derived from best expected limit BR excluded at 95% C.L in the 10-2:10-1 pb range e e  A. Canepa

  12. N jets 0LS leptons (I) Expect high cross sections Weak experimental limits ! SM + Max Flavor Violation  SM + scalar doublet Events with 2 LS muons (electrons) pT (ET) > 20 GeV, MET > 20 GeV, 1 b-tagged jet 2.0 fb-1 SIGNAL 2 like-sign leptons, 2 neutrinos, 1 b-jet and 0,1 or 2 light jets A. Canepa

  13. 0LS leptons (II) • Assume + heavy  not accessible at TeV •  real and 31= 13 • 0  ut dominant decay Binned likelihood fit of jet multiplicity to extract the signal Exclude natural values of ξ=1 at low masses A. Canepa

  14. Summary CDF explored up to 2.5 fb-1 of Tevatron collision data searching for high mass resonances decaying into leptons No signal of New Physics seen • World best limits set on Z’, RS gravitons, sneutrino • More data to be analyzed in the next years! For updates, http://www-cdf.fnal.gov/physics/exotic/exotic.html A. Canepa

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