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 ¯ ¯ Lorenzo Moneta Moriond QCD 17-23 March 2001

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 Lorenzo Moneta Moriond QCD 17-23 March 2001

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

SM H0 production @ Tevatron 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 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 Lorenzo Moneta Moriond QCD 17-23 March 2001

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

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

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 b e,µ (in jets) 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 Lorenzo Moneta Moriond QCD 17-23 March 2001

Search for mbb 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 CDF 1 b-tag 2 b-tags mbb ~ 0.2 – 0.3 % 6 3  1 2 b-tags CDF ~ 0.6 - 0.9 % 27 25  3 1 b-tag D ~ 0.6 – 0.8 % 36 30  5 Br x accept. (90<m(H)<130) data backg channel Exp. from fit to di-jets mass: 95% CL Limit on sBR: 26-28 pb for 90<MH<130 (CDF) 40-19 pb for 90<MH<120 (D) Lorenzo Moneta Moriond QCD 17-23 March 2001

Search for 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) ~ 0.4 – 0.5 % 4 4  1 2 b-tags CDF ~ 0.5 – 0.8 % 40 39  4 1 b-tag Br x accept. (90<m(H)<130) data backg channel Exp. 95% CL Limit on sBR: ~ 8 pb for 90<MH<130 Lorenzo Moneta Moriond QCD 17-23 March 2001

Search for mbb 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) mbb ~ 0.2 % 5 3  1 1 b-tag CDF Br x accept. (90<m(H)<130) data backg channel Exp. 95% CL Limit on sBR: 56-24 pb for 90<MH<130 Lorenzo Moneta Moriond QCD 17-23 March 2001

Search for mbb 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) ¯ mbb ~ 1.5 – 2.9 % 589 ~ 600 2 b-tag CDF Br x accept. (90<m(H)<130) data back. channel Exp. 95% CL Limit on sBR: 30-16 pb for 90<MH<130  Need good Mbb resolution against background Lorenzo Moneta Moriond QCD 17-23 March 2001

Combined limit for SM Higgs CDF combination of 95 % CL limit on slimit = 7.4-8.2 pb for mH = 90-130 GeV/c2 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 ¯ ¯ ¯ LEP ¯ SM 115 Lorenzo Moneta Moriond QCD 17-23 March 2001

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 Lorenzo Moneta Moriond QCD 17-23 March 2001

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

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) ¯ 0.28 % 2 3.5  1.1 120 0.59 % 0.1  0.4 300 0.16 % 5 4.6  1.4 70 Br x accept. data backg BR x acc. M(j) (GeV) ¯ Lorenzo Moneta Moriond QCD 17-23 March 2001

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

Charged Higgs Searches 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-tbar evts 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 Lorenzo Moneta Moriond QCD 17-23 March 2001

Charged Higgs Searches 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 D0 LEP2 (ADLO) New Exclusion regions at low and high tanb Lorenzo Moneta Moriond QCD 17-23 March 2001

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 g in 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 Lorenzo Moneta Moriond QCD 17-23 March 2001

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) Lorenzo Moneta Moriond QCD 17-23 March 2001