Hiroshima Higgs Workshop 2006 Jan 17 19 2006

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Higgs Searches at the Tevatron Kazuhiro Yamamoto (Osaka City University) for the CDF Collaboration 1. 2. 3. 4. Tevatron and CDF SM Higgs MSSM Higgs Future Prospects

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Introduction • Higgs boson – Last missing brick in the SM – Indispensable for • Generating masses of particles • Keeping theory renormalizable at EW scale – Junction piece to the beyond-SM Standard Model (SM) ü One neutral higgs : h Minimal Supersymmetric Extension of Standard Model (MSSM) ü Two higgs doublet gives • Two neutral CP-even : h, H • One neutral CP-odd : A • Two charged : H+, H-

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Tevatron Accelerator Complex CDF D 0 Tevatron • • Main Injector and Recycler • s = 1. 96 Te. V # of p and p bunches : 36 x 36 Bunch spacing : 396 ns Recycler as the 2 nd p accumulator Recently implemented new technology : – Slip stacking (MI) – Electron cooling (Recycler)

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Tevatron Status • 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 World record of hadron collider – weekly integrated : 26 pb-1 • Integrated luminosity : – 1540 pb-1 delivered – 1230 pb-1 on tape – 360 pb-1 analyzed ( as of Jan. 2008)

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 CDF II Detector

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 SM Higgs at the Tevatron • • pp collision, s = 1. 96 Te. V Gluon fusion • Vector-boson associated production • Huge QCD background gg h : 0. 7 pb (Mh = 120 Ge. V/c 2) qq’ Wh : 0. 16 pb (Mh = 120 Ge. V/c 2) qq Zh : 0. 10 pb (Mh = 120 Ge. V/c 2) – Need triggering on high-p. T leptons from W/Z’s or higgs

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 SM Higgs Decay • Low mass Higgs (< 130 Ge. V/c 2) – bb dominant reconstruction of 2 b jets – gg h bb swamps on QCD background – Vh production is promising • High mass Higgs (130 ~ 200 Ge. V/c 2) – WW dominant multi-lepton signature

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 SM Higgs Search at CDF • Analysis-ongoing channels 320 pb-1 analysis done Analysis in progress 290 pb-1 analysis done 360 pb-1 analysis done 194 pb-1 analysis done

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • • • Signature – High p. T isolated lepton + missing ET + 2 jets Selection – ISOcal < 0. 1 p – Missing ET > 20 Ge. V – 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

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 95% C. L. upper limits on the WH cross section Dijet invariant mass in the inclusive single tag sample

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 b-jet Missing ET y x b-jet • • Most sensitive channel in Run I and recent analyses at CDF Large missing ET Two jets (at least one b-tag) Selection – 1 st jet ET > 40 Ge. V, 2 nd jet ET > 20 Ge. V, no other jets w/ ET > 15 Ge. V – Missing ET > 70 Ge. V – At least one b-tagged jet

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • Blind analysis on Df (Missing ET, 2 nd Jet) and lepton existence • Control Region 1 – QCD h. f. • Control Region 2 - EWK

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • Signal Region • Consistent with SM • Observed 6 events b/w 80 ~ 120 Ge. V/c 2 for 120 Ge. V Higgs. • 95% C. L. upper limit on the ZH production

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 MH=160 Ge. V/c 2 • • • Large cross section of gluonfusion and large branching fraction of H WW at large MH Search for high p. T opposite sign dilepton with large missing ET Scalar nature of Higgs results in angular alignment between final state leptons. Small dilepton invariant mass

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • Binned maximum likelihood method on the Df distribution to extract the signal production limit. • 95% C. L. upper limit on the Higgs production

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • • • Search for like-sign dilepton having at least one high-p. T lepton Good signature to discriminate non. Higgs SM events – Most SM events result in opposite sign Understanding fake leptons and conversion electrons was necessary.

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • Signal search on the p. T 12 and p. T 2 plane. • 95% C. L. upper limit on the WH production – p. T 12 : vector sum of p. T of the leading lepton and the 2 nd leading lepton – p. T 2 : p. T of the 2 nd leading lepton Update with higher luminosity is ongoing.

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Summary of the Cross Section Limits on Higgs Production at the Tevatron • • Analyses with 200 ~ 300 pb-1 data completed. Updates with 500 pb-1 ~ 1 fb-1 are in progress. Run II goal is 8 fb-1.

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Limit from indirect measurements • • • Relation among MW, Mt, and MH via the radiative correction MW = 80. 410 0. 032 Ge. V/c 2 New result of Mt from CDF/D 0 : Mt = 172. 7 2. 9 Ge. V/c 2

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Limit from indirect measurements (2) • EW global fit by LEP EWWG MH < 186 Ge. V/c 2 @ 95% C. L. • SM or MSSM ? MSSM is favorable for now.

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 MSSM Higgs at the Tavatron • Neutral Higgs at large tanb : – f (= h/H/A) and f. Z production suppressed. – gg/bb f, gg/qq’ fbb enhanced by ~ (1/cosb)2 ~ tan 2 b. – 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 tb. H+

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 MSSM Higgs Search at CDF • Analysis-ongoing Channels Analysis in progress 310 pb-1 analysis done 192 pb-1 analysis done

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • Selection of tt events – – • One t decays to e or m (te or tm) The other t decays to hadrons (th) Requirements – – – ET > 10 Ge. V, p. T > 8 Ge. V/c for e p. T > 10 Ge. V/c for m For hadronic t : • Isolated narrow jet • No tracks b/w 10 o and 30 o from • • • the seed track Jet invariant mass < 1. 8 Ge. V/c 2 Opposite electric charge against e or m 1 or 3 tracks in the inside cone

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • Visible mass distribution • Consistent with SM expectation - 8. 4± 0. 9 expected, 11 observed • Calculated 95% C. L. upper limit on the cross section times branching ratio by fitting mass spectrum for Higgs signal.

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • • Interpret the cross section limit as constraints of MA and tanb. Benchmark cases of m < 0 (-200) and m > 0 (+200).

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • • • 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.

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • • 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 Observed events Background Expected SM events dilepton 13 2. 7± 0. 7 11 lepton + jets (exactly 1 b-tag) 49 20. 3± 2. 5 54 lepton + jets ( >=2 b-tags) 8 0. 94± 0. 17 10 lepton + tau 2 13± 0. 2 2 No discrepancy to SM

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 • • Obtained constraints on the tanb – MH+ plane. Two benchmark cases for typical SUSY parameters below: At = Ab = m/tanb A t = Ab = sqrt(6)MSUSY + m/tanb MSUSY = 800 Ge. V/c 2, m = -200 Ge. V/c 2, At = 500 Ge. V/c 2, M 1 = 0. 498*M 2, M 2 = 200 Ge. V/c 2, M 3 = 800 Ge. V/c 2, MQ = MU = MD = ME = ML = MSUSY • Same scenarios as h 0 search by LEP 2 (hep-ph/9912223)

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Future Prospects • Tevatron upgrade Luminosity is steadily increasing ! Luminosity upgrading plan

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 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 FY 04) We are on the track of the design plan for now !

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Future Prospects (3) • SM Higgs Sensitivity Projection • For MH = 115 Ge. V – ~2 fb-1 for exclusion – ~4 fb-1 for 3 s evidence • Assumption – All Higgs channels combined at CDF and D 0 – No systematics

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Future Prospects (4) • MSSM Neutral Higgs Sensitivity Projection CDF Run II Preliminary • • • 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

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Conclusions • Tevatron luminosity is steadily increasing. – More than 1 fb-1 has already been delivered. • ~300 pb-1 analyses completed. – Data being processed for 1 fb-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 …

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Backup Slides

Hiroshima Higgs Workshop 2006, Jan. 17 – 19, 2006 Improvement WH lnbb ZH nnbb ZH llbb Mass resolution 1. 7 Continuous b-bag (NN) 1. 5 Forward b-tag 1. 1 Forward leptons 1. 3 1. 0 1. 6 Track-only leptons 1. 4 1. 0 1. 6 1. 75 1. 0 WH signal in ZH 1. 0 2. 7 1. 0 Product of above 8. 9 13. 3 7. 2 CDF + D 0 combination 2. 0 17. 8 26. 6 14. 4 NN selection All combined