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Higgs Searches at the Tevatron

Higgs Searches at the Tevatron. Kazuhiro Yamamoto (Osaka City University) for the CDF Collaboration. Tevatron and CDF SM Higgs MSSM Higgs Future Prospects. Introduction. Higgs boson Last missing brick in the SM Indispensable for Generating masses of particles

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Higgs Searches at the Tevatron

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  1. Higgs Searches at the Tevatron Kazuhiro Yamamoto (Osaka City University) for the CDF Collaboration • Tevatron and CDF • SM Higgs • MSSM Higgs • Future Prospects

  2. Introduction • Higgs boson • Last missing brick in the SM • Indispensable for • Generating masses of particles • Keeping the theory renormalizable at EW scale • Junction piece to the beyond-SM • Standard Model (SM) • One neutral higgs : h • Minimal Supersymmetric Extension • of Standard Model (MSSM) • Two higgs doublet gives • Two neutral CP-even : h, H • One neutral CP-odd : A • Two charged : H+, H-

  3. s = 1.96 TeV # of p and p bunches : 36 x 36 Bunch spacing : 396 ns Recycler as the 2ndp accumulator Recently implemented new technology : Slip stacking (MI) Electron cooling (Recycler) Tevatron Accelerator Complex CDF D0 Tevatron Main Injector and Recycler

  4. Achieving typical luminosity of : peak : 1.5 ~ 1.7 x 1032 cm-2 s-1 weekly integrated : 15 ~ 20 pb-1 Run II record luminosity : peak : 1.79 x 1032 cm-2 s-1 weekly integrated : 26 pb-1 Integrated luminosity : 1540 pb-1 delivered 1230 pb-1 on tape 360 pb-1 analyzed ( as of Jan. 2008) Tevatron Status World record of hadron collider

  5. CDF II Detector

  6. SM Higgs at the Tevatron • pp collision, s = 1.96TeV • Gluon fusiongg h : 0.7 pb (Mh = 120 GeV/c2) • Vector-boson associated production qq’Wh : 0.16 pb (Mh = 120 GeV/c2) qqZh : 0.10 pb (Mh = 120 GeV/c2) • Huge QCD background • Need triggering on high-pT leptons from W/Z’s or higgs

  7. SM Higgs Decay • Low mass Higgs (< 130 GeV/c2) • bb dominant  reconstruction of 2b jets • gghbb swamps on QCD background • Vh production is promising • High mass Higgs (130 ~ 200 GeV/c2) • WW dominant  multi-lepton signature

  8. SM Higgs Search at CDF • Analysis-ongoing channels

  9. Signature High pT isolated lepton + missing ET + 2 jets Selection ISOcal < 0.1p Missing ET > 20 GeV 2 taggable jets (require 1 or more b-tags) Single b-tag is more sensitive Example of double b-tagged events with large missing ET

  10. 95% C.L. upper limits on the WH cross section Dijet invariant mass in the inclusive single tag sample

  11. Most sensitive channel in Run I and recent analyses at CDF Large missing ET Two jets (at least one b-tag) Selection 1st jet ET > 40 GeV, 2nd jet ET > 20 GeV, no other jets w/ ET > 15 GeV Missing ET > 70 GeV At least one b-tagged jet b-jet Missing ET y x b-jet

  12. Blind analysis on Df (Missing ET, 2nd Jet) and lepton existence • Control Region 1 – QCD h. f. • Control Region 2 - EWK

  13. Signal Region 95% C.L. upper limit on the ZH production • Consistent with SM • Observed 6 events b/w 80 • ~ 120 GeV/c2 for 120 GeV Higgs.

  14. Large cross section of gluon-fusion and large branching fraction of H WW at large MH Search for high pT opposite sign dilepton with large missing ET Scalar nature of Higgs results in angular alignment between final state leptons.  Small dilepton invariant mass MH=160GeV/c2

  15. Binned maximum likelihood method on the Df distribution to extract the signal production limit. 95% C.L. upper limit on the Higgs production

  16. Search for like-sign dilepton having at least one high-pT lepton Good signature to discriminate non-Higgs SM events Most SM events result in opposite sign Understanding fake leptons and conversion electrons was necessary.

  17. Signal search on the pT12 and pT2 plane. pT12 : vector sum of pT of the leading lepton and the 2nd leading lepton pT2 : pT of the 2nd leading lepton 95% C.L. upper limit on the WH production Update with higher luminosity is ongoing.

  18. Summary of the Cross Section Limits on Higgs Production at the Tevatron • Analyses with 200 ~ 300pb-1 data completed. • Updates with 500pb-1 ~ 1fb-1 are in progress. Run II goal is 8fb-1.

  19. Limit from indirect measurements • Relation among MW, Mt, and MH via the radiative correction • MW = 80.410  0.032 GeV/c2 • New result of Mt from CDF/D0 : Mt = 172.7  2.9 GeV/c2

  20. EW global fit by LEP EWWG SM or MSSM ? Limit from indirect measurements (2) MSSM is favorable for now. MH < 186 GeV/c2 @ 95% C.L.

  21. Neutral Higgs at large tanb : f (= h/H/A) and fZ production suppressed. gg/bbf, gg/qq’fbb enhanced by ~ (1/cosb)2 ~ tan2b. Br(ftt)  10% Br(fbb)  90% in a wide mass range. Charged Higgs MH+ < Mt – Mb tH+b MH+ > Mt – Mb pptbH+ MSSM Higgs at the Tavatron

  22. MSSM Higgs Search at CDF • Analysis-ongoing Channels

  23. Selection of tt events One t decays to e or m (te or tm) The other t decays to hadrons (th) Requirements ET > 10 GeV, pT > 8GeV/c for e pT > 10 GeV/c for m For hadronic t : Isolated narrow jet No tracks b/w 10o and 30o from the seed track Jet invariant mass < 1.8GeV/c2 Opposite electric charge against e or m 1 or 3 tracks in the inside cone

  24. Visible mass distribution Calculated 95% C.L. upper limit on the cross section times branching ratio by fitting mass spectrum for Higgs signal. • Consistent with SM expectation • - 8.4±0.9 expected, 11 observed

  25. Interpret the cross section limit as constraints of MA and tanb. • Benchmark cases of m < 0 (-200) and m > 0 (+200).

  26. When MH± < Mt + Mb, a top quark can decay to a charged higgs. • Charged higgs decays to tn, cs, t*b  Wbb, and Wh(A)  Wbb. • This gives discrepancy to SM t Wb decay ratio.

  27. If a charged higgs exists, anomaly appears in the top cross section and the final state components. • 4 channels used for H± search with 192 pb-1. Latest CDF results No discrepancy to SM

  28. Obtained constraints on the tanb – MH+ plane. • Two benchmark cases for typical SUSY parameters below: At = Ab = m/tanb At = Ab = sqrt(6)MSUSY + m/tanb MSUSY = 800 GeV/c2, m = -200 GeV/c2, At = 500 GeV/c2, M1 = 0.498*M2, M2 = 200 GeV/c2, M3 = 800 GeV/c2, MQ = MU = MD = ME = ML = MSUSY • Same scenarios as h0 search by LEP2 (hep-ph/9912223)

  29. Future Prospects • Tevatron upgrade Luminosity upgrading plan Luminosity is steadily increasing !

  30. Future Prospects (2) • Tevatron upgrade (2) We are here ! Red line : Design plan (All technical challenges success) Blue line : Base plan (Simple extrapolation as of the end of FY04) We are on the track of the design plan for now !

  31. SM Higgs Sensitivity Projection For MH = 115 GeV ~2fb-1 for exclusion ~4fb-1 for 3s evidence Assumption All Higgs channels combined at CDF and D0 No systematics Future Prospects (3)

  32. MSSM Neutral Higgs Sensitivity Projection Sensitivity for CDF and DO combined. Same techniques and same channels as current analysis assumed. Improvements expected with investigating : fthth and tetm ppfbbbbbb Future Prospects (4) CDF Run II Preliminary CDF Run II Preliminary

  33. Conclusions • Tevatron luminosity is steadily increasing. • More than 1fb-1 has already been delivered. • ~300pb-1 analyses completed. • Data being processed for 1fb-1 challenge. (Planning to show some results in the summer conf. this year.) • Obtained some cross section limits on SM and MSSM Higgs bosons. • Can we see any signs of Higgs before the LHC ? • Need to do all we can do …

  34. Backup Slides

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