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Higgs Searches at the Tevatron (Run I )

Higgs Searches at the Tevatron (Run I ). Lorenzo Moneta University of Geneva on behalf of CDF and D  collaboration. Introduction SM Higgs ZH & WH with H  bb (CDF & D  ) MSSM Higgs bb f with f =H 0 ,h 0 ,A 0 (CDF) H + (CDF & D  ) Fermiophobic Higgs

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Higgs Searches at the Tevatron (Run I )

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  1. Higgs Searches at the Tevatron (Run I) Lorenzo Moneta University of Geneva on behalf of CDF and D collaboration • Introduction • SM Higgs • ZH & WH with H  bb (CDF & D) • MSSM Higgs • bbf with f=H0,h0,A0 (CDF) • H+ (CDF & D) • Fermiophobic Higgs • H  gg (CDF & D) • Conclusions ¯ ¯ Moriond QCD 17-23 March 2001

  2. Introduction • Electroweak Symmetry breaking in the SM predicts existence of an Higgs boson but with unspecified mass • Higgs mass constraints scale  where SM might break down • if  = MPlank then 130 < M(H) < 180 Current Status of Higgs searches • SM fit to Electroweak data indicates a light Higgs • M(H) < ~ 200 GeV @ 95 % CL • Direct searches from LEP2 • 95 % CL limit is ~ 113 GeV • Indication of Higgs-like events in the last year data: excess ~ 3 at M(H) 115 GeV Moriond QCD 17-23 March 2001

  3. Run I (Oct. 92  Feb. 96) total integrated luminosity ~ 120-1 pb / detector Tevatron proton-antiproton collision @ s = 1.8 TeV Silicon Vertex Detector Tevatron (Run I) CDF DØ Expected ~ 2 fb-1 in Run IIa ! Moriond QCD 17-23 March 2001

  4. Gluon Fusion too difficult (QCD background) Higgsstrahlung SM cross section is very small 1/20 s(t-tbar) 1/500 s(Z/W +  2 jets) possible with Run II luminosity ! larger s with new physics ?? LEP SM H0 production @ Tevatron s = 0.70 pb for M(H) = 120 Gev/c2 with QCD NLO correction WH: s= 0.16 pb ZH: s= 0.10 pb • Vector Boson fusion • radiation off heavy quark • very small s in the SM Moriond QCD 17-23 March 2001

  5. M(H) < 130 GeV dominant decay is final states are for W/ZH need lepton ID/MET + b-tags M(H) > 130 GeV dominant decay is final state with  2 leptons but smaller cross-section interesting at RunII ! LEP SM Higgs decays For M(H) = 120 GeV/c2 Moriond QCD 17-23 March 2001

  6. Tevatron Run I channels : (W/Z + H with M(H) < 130 GeV) BG: QCD multijets BG: BG: QCD, BG: SM H signatures (W /Z + H) ( 50% of W/Z H ) ( 9% ) ( 5.4%) ( 1.8%) • Essential for these analyses: • b tagging • good di-jet mass resolution Moriond QCD 17-23 March 2001

  7. b e,µ (in jets) b tagging at the Tevatron Techniques developed for top analyses. Two algorithms: • Soft Lepton Tagging (SLT)(CDF & DØ) • semileptonic b decays: • DØ:m( pT > 4 GeV) CDF: m & e (pT > 2 GeV) • Secondary Vertex Tagging (SVX)(CDF) • reconstruct a displaced vertex in the jet • b lifetime ~ 1.5 ps  decay length ~ few mm • use capability of Silicon vertex detectors e(b-tag) ~ 7%/b-jet e(mistag) ~ 0.5%/jet s(decay-length) ~ 100 mm b jet e(b-tag) ~ 20%/b-jet e(mistag) ~ 0.2%/jet secondary vertex primary vertex Moriond QCD 17-23 March 2001

  8. Final states are lepton (e/m) + MET + b’s Event selection: high pTlepton: pT(lep) > 20 GeV & h<1 MET>20 2 jets with ET(j)>15, h<2 b-tags (single OR double jet tag) Backgrounds: Results (CDF & D) 106 pb-1 Exp. channel backg data Br x accept. (90<m(H)<130) CDF 1 b-tag 30  5 36 ~ 0.6 – 0.8 % CDF 2 b-tags 3  1 6 ~ 0.2 – 0.3 % D 1 b-tag 25  3 27 ~ 0.6 - 0.9 % Search for CDF 1 b-tag 2 b-tags mbb from fit to di-jets mass: 95% CL Limit on sBR: 26-28 pbfor 90<MH<130 (CDF) 40-19pbfor 90<MH<120 (D) Moriond QCD 17-23 March 2001

  9. Final states is MET + b’s Event selection (CDF): MET>40 (trigger >35) + lepton veto 2 or 3 jets with ET(j)>15, <2 DF(MET,j) > 60° for all jets (ET>8) DF(j1,j2) < 150° b-tags (single OR double) Backgrounds: QCD and Results (88 pb-1) Exp. channel backg data Br x accept. (90<m(H)<130) CDF 1 b-tag 39  4 40 ~ 0.5 – 0.8 % CDF 2 b-tags 4  1 4 ~ 0.4 – 0.5 % Search for 95% CL Limit on sBR: ~ 8 pb for 90<MH<130 Moriond QCD 17-23 March 2001

  10. Final states is di-leptons + b’s Event selection (CDF): pT(lep)>20,10 GeV 76<M(l,l)<106 GeV 2 or 3 jets with ET(j)>15, h<2 MET < 50 GeV (against top di-lepton evts) 1 b-tag Backgrounds: Results (106 pb-1) Exp. channel backg data Br x accept. (90<m(H)<130) CDF 1 b-tag 3  1 5 ~ 0.2 % Search for mbb 95% CL Limit on sBR: 56-24 pb for 90<MH<130 Moriond QCD 17-23 March 2001

  11. Multi-jet final state with b’s Event selection (CDF): Multi-jets trigger  4 jets with SET>125 GeV & ET>15 double b-tag pT(bb)>50 GeV Backgrounds: mainly QCD (b’s + fakes) also top and Z + jets Results (91 pb-1) Exp. channel back. data Br x accept. (90<m(H)<130) CDF 2 b-tag ~ 600 589 ~ 1.5 – 2.9 % Search for ¯ mbb 95% CL Limit on sBR: 30-16 pb for 90<MH<130  Need good Mbb resolution against background Moriond QCD 17-23 March 2001

  12. CDF combination of 95 % CL limit on x 30 SM cross-section (mH = 115) Limit is dominated by nnbb Expected best limits from: nnbb and lnbb poor lnbb limit due to a small excess in observed events Need more luminosity RUN II Combined limit for SM Higgs slimit= 7.4-8.2 pb for mH = 90-130 GeV/c2 ¯ ¯ ¯ LEP ¯ SM 115 Moriond QCD 17-23 March 2001

  13. MSSM Higgs Search Two Higgs doublets in the MSSM • 5 Higgs particles • two neutral CP-even: h0,H0 • One neutral CP odd: A0 • Two charged: H+,H- • two free parameters: tanb and mA • Mass relations at tree level: • m(h0) < m(Z0) < m(H0); m (A0) < m(H0); m(H+) < m(W) • but after radiative corrections m(h0) < 130 GeV • Couplings at large tanb: • enhanced to d-type quark and leptons • suppressed to u-type quark Moriond QCD 17-23 March 2001

  14. Small tanb : SM-like cross-sections Large tanb enhanced hbb coupling hbb/Hbb/Abb can have large cross-sections ( tan2b) MSSM Higgs production tanb= 3 tanb= 30 h h H H s(pb) s(pb) ¯ ¯ ¯ ¯ ¯ In general dominant Higgs’s Branching Ratio are to bb (90%) and t+t-(10%) Moriond QCD 17-23 March 2001

  15. M(j) (GeV) BR x acc. backg data Br x accept. 70 0.16 % 4.6  1.4 5 0.16 % 120 0.28 % 3.5  1.1 2 0.28 % 300 0.59 % 0.1  0.4 0 0.59 % Search for ¯ • Exploit enhanced Yukawa couplings looking for bb production (j = h,HA) • large cross sections ( tanb2) • 4-b’s jets final state • Event selection (CDF): • Multi-jets trigger • 4 jets with S(ET)>125 GeV & ET>15 • ET(j) cuts depending on m(j) •  3 b-tags • DF(bb) > 109° (against gbb) • Backgrounds: • QCD (bb/cc), Z/Wjj, top CDF results (91 pb-1) ¯ ¯ Moriond QCD 17-23 March 2001

  16. Limit for sBR < 25.7 pb • Limit (95%CL for Mj = 100 GeV): • convert sBR limit in tanb vs Higgs mass exclusion • No mixing & Maximal Mixing for the stop tanb vs m(h) tanb vs m(A) Tevatron complements LEP ! Moriond QCD 17-23 March 2001

  17. Searches for t H+b when M(H+) < mt - mb decay t H+b can compete with SM decay t W+b BR(t H+b) depends on tanb Direct Search (CDF): look for H+  tn in t-tbarevts BR(H+ tn) ~ 1 for large tanb WHbb or HHbb channels in addition to WWbb look for l + t+ MET + jj events (l = e,m,t) use t identifications via hadronic decays (tracking + calorimeter) backgrounds: Z  tt + jj, W+3 jets, WW/WZ acceptances for single and double H production Charged Higgs Searches Moriond QCD 17-23 March 2001

  18. Indirect Search (CDF + D) look for lepton disappearance in t-tbar events suppression of dileptons and lepton + jets events rate of the two depends on BR(t  H+b) t-tbar cross-section independent of m(H), tanb given measured x-section (when BR(t  H+b) = 0) exclusion regions in the m(H+)-tanb plane Charged Higgs Searches D0 LEP2 (ADLO) New Exclusion regions at low and high tanb Moriond QCD 17-23 March 2001

  19. Fermiophobic Higgs • In some models Higgs couples only to vector bosons • BR(H  gg) dominant for light Higgs (m(H) < 100) • Searches for W/Z + H  ggjj • D search: • di-photons + jets • Backgrounds from QCD • fakes or real gin jets • CDF search • di-photons with e/m + MET or jj • Limit For SM cross-section: • M(H) > ~ 80 GeV (95% CL) • LEP limit is ~ 105 GeV D0 Moriond QCD 17-23 March 2001

  20. Conclusions • SM Higgs searches are luminosity limited in Run I • no sensitivity to SM cross sections • no excess seen and set limits at ~30 SM cross-section • provided experience for Run II • developed techniques for low mass Higgs searches • b tagging and di-jet mass resolution are crucial ! • good expectations for Run II • see next talk on Run II prospects • Nice exclusion results for MSSM Higgs: • bbj search with sensitivity for high tanb region • charged Higgs from t  H+b • probed regions inaccessible to LEP • very interesting in Run II report of the Tevatron Higgs Working Group (hep-ph/0010338) Moriond QCD 17-23 March 2001

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