Higgs Searches at the Tevatron Run I Lorenzo

Higgs Searches at the Tevatron (Run I) Lorenzo Moneta University of Geneva on behalf of CDF and D collaboration • Introduction • SM Higgs ¯ (CDF & D ) – ZH & WH with H bb • MSSM Higgs ¯ with f=H 0, h 0, A 0 (CDF) – bbf – H+ (CDF & D ) • Fermiophobic Higgs – H gg (CDF & D ) • Conclusions Lorenzo Moneta Moriond QCD 17 -23 March 2001 1

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 Ge. V @ 95 % CL • Direct searches from LEP 2 – 95 % CL limit is ~ 113 Ge. V – Indication of Higgs-like events in the last year data: excess ~ 3 at M(H) 115 Ge. V Lorenzo Moneta Moriond QCD 17 -23 March 2001 2

Tevatron (Run I) Tevatron proton-antiproton collision @ s = 1. 8 Te. V CDF DØ Run I (Oct. 92 Feb. 96) Silicon Vertex Detector total integrated luminosity ~ 120 -1 pb / detector Expected ~ 2 fb-1 in Run IIa ! Lorenzo Moneta Moriond QCD 17 -23 March 2001 3

SM H 0 production @ Tevatron • Gluon Fusion = 0. 70 pb for M(H) = 120 Gev/c 2 with QCD NLO correction – too difficult (QCD background) • Higgsstrahlung WH: = 0. 16 pb ZH: = 0. 10 pb – SM cross section is very small • 1/20 (t-tbar) • 1/500 (Z/W + 2 jets) – possible with Run II luminosity ! – larger with new physics ? ? Lorenzo Moneta LEP • • Vector Boson fusion radiation off heavy quark Moriond QCD 17 -23 March 2001 • very small in the SM 4

SM Higgs decays • M(H) < 130 Ge. V – dominant decay is – final states are for W/ZH – need lepton ID/MET + b-tags • M(H) > 130 Ge. V – dominant decay is – final state with 2 leptons LEP For M(H) = 120 Ge. V/c 2 – but smaller cross-section • interesting at Run. II ! Lorenzo Moneta Moriond QCD 17 -23 March 2001 5

SM H signatures (W /Z + H) Tevatron Run I channels : (W/Z + H with M(H) < 130 Ge. V) • ( 50% of W/Z H ) – BG: QCD multijets • ( 9% ) – BG: • ( 5. 4%) – BG: QCD, • ( 1. 8%) – BG: Lorenzo Moneta Essential for these analyses: • b tagging • good di-jet mass resolution Moriond QCD 17 -23 March 2001 6

b tagging at the Tevatron Techniques developed for top analyses. Two algorithms: – Soft Lepton Tagging (SLT) (CDF & DØ) • semileptonic b decays: b • DØ: m ( p. T > 4 Ge. V) CDF: m & e (p. T > 2 Ge. V) e, µ (in jets) e(b-tag) ~ 7%/b-jet e(mistag) ~ 0. 5%/jet – 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 (decay-length) ~ 100 mm b jet primary vertex Lorenzo Moneta secondary vertex Moriond QCD 17 -23 March 2001 e(b-tag) ~ 20%/b-jet e(mistag) ~ 0. 2%/jet 7

Search for • Final states are lepton (e/m) + MET + b’s • Event selection: – – CDF high p. Tlepton: p. T(lep) > 20 Ge. V & <1 MET>20 2 jets with ET(j)>15, <2 b-tags (single OR double jet tag) 1 b-tag • Backgrounds: 2 b-tags – 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 % Lorenzo Moneta mbb from fit to di-jets mass: 95% CL Limit on BR: 26 -28 pb for 90<MH<130 (CDF) 40 -19 pb for 90<MH<120 (D ) Moriond QCD 17 -23 March 2001 8

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(j 1, j 2) < 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 % Lorenzo Moneta Moriond QCD 17 -23 March 2001 95% CL Limit on BR: ~ 8 pb for 90<MH<130 9

Search for • Final states is di-leptons + b’s • Event selection (CDF): – p. T(lep)>20, 10 Ge. V – 76<M(l, l)<106 Ge. V – 2 or 3 jets with ET(j)>15, <2 – MET < 50 Ge. V (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 % Lorenzo Moneta Moriond QCD 17 -23 March 2001 mbb 95% CL Limit on BR: 56 -24 pb for 90<MH<130 10

Search for • Multi-jet final state with b’s • Event selection (CDF): – Multi-jets trigger • 4 jets with SET>125 Ge. V & ET>15 – double b-tag ¯ – p. T(bb)>50 Ge. V • 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 % Need good Mbb resolution against background Lorenzo Moneta Moriond QCD 17 -23 March 2001 mbb 95% CL Limit on BR: 30 -16 pb for 90<MH<130 11

Combined limit for SM Higgs CDF combination of 95 % CL limit on limit = 7. 4 -8. 2 pb for m. H = 90 -130 Ge. V/c 2 • x 30 SM cross-section (m. H = 115) LEP SM 115 Lorenzo Moneta ¯ • Limit is dominated by nnbb • Expected best limits from: – ¯ and lnbb ¯ nnbb ¯ limit due to a small • poor lnbb excess in observed events • Need more luminosity – RUN II Moriond QCD 17 -23 March 2001 12

MSSM Higgs Search Two Higgs doublets in the MSSM – 5 Higgs particles • two neutral CP-even: h 0, H 0 • One neutral CP odd: A 0 • Two charged: H+, H- – two free parameters: tanb and m. A – Mass relations at tree level: • m(h 0) < m(Z 0) < m(H 0); m (A 0) < m(H 0); m(H+) < m(W) • but after radiative corrections m(h 0) < 130 Ge. V – Couplings at large tanb: • enhanced to d-type quark and leptons • suppressed to u-type quark Lorenzo Moneta Moriond QCD 17 -23 March 2001 13

MSSM Higgs production h h H H tanb = 30 (pb) tanb = 3 • Small tanb : • Large tanb – SM-like cross-sections ¯ coupling – enhanced hbb ¯ ¯ ¯ can have large – hbb/Hbb/Abb cross-sections ( tan 2 b) ¯ (90%) and t+t- (10%) In general dominant Higgs’s Branching Ratio are to bb Lorenzo Moneta Moriond QCD 17 -23 March 2001 14

Search for ¯ production ( • Exploit enhanced Yukawa couplings looking for bb = h, HA) • large cross sections ( tanb 2) • 4 -b’s jets final state • Event selection (CDF): – Multi-jets trigger • 4 jets with S(ET)>125 Ge. V & ET>15 – ET(j) cuts depending on m( ) – 3 b-tags ¯ > 109° (against g bb) – DF(bb) • Backgrounds: – ¯ QCD (bb/cc), Z/Wjj, top Lorenzo Moneta CDF results (91 pb-1) M( ) (Ge. V) 70 BR x acc. backg data 0. 16 % 4. 6 1. 4 5 120 0. 28 % 3. 5 1. 1 2 300 0. 59 % 0. 1 0. 4 0 Moriond QCD 17 -23 March 2001 15

Limit for • Limit (95%CL for M = 100 Ge. V): BR < 25. 7 pb • convert 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 ! Lorenzo Moneta Moriond QCD 17 -23 March 2001 16

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 17

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 D 0 LEP 2 (ADLO) New Exclusion regions at low and high tanb Lorenzo Moneta Moriond QCD 17 -23 March 2001 18

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 D 0 – fakes or real g in jets – CDF search • di-photons with e/m + MET or jj • Limit For SM cross-section: M(H) > ~ 80 Ge. V (95% CL) • LEP limit is ~ 105 Ge. V Lorenzo Moneta Moriond QCD 17 -23 March 2001 19

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 report of the Tevatron Higgs Working Group (hep-ph/0010338) • Nice exclusion results for MSSM Higgs: – – bb search with sensitivity for high tanb region charged Higgs from t H+b probed regions inaccessible to LEP very interesting in Run II Lorenzo Moneta Moriond QCD 17 -23 March 2001 20