Higgs Searches at the Tevatron: Run I

CDF D0 Ho Higgs Searches at the Tevatron: Run I Jacobo Konigsberg / Univ. of Florida / CDF Introduction The Higgs Run I SM Higgs (CDF/D0) ZHo & WHo MSSM Higgs bbj ; j=Ho,ho,Ao(CDF) H+(CDF/D0) More beyond Bosophilic(CDF/D0) Conclusions

[an] EWSB mechanism in SM Gives mass to particles through H couplings H mass unspecified in SM but couplings are specified Mtop, MW and MHiggs related via higher order loops Current data points to light Higgs MHiggs < 170 GeV @ 95%, Osaka’00 Higgs-like events observed at LEP2 before shutdown: ~114 GeV 95% CL exclusion limit The Higgs mass constraints the scale where the SM might break down () 130<MH<180 GeV/c2  = Mplank Possible to discover at Tevatron in the next few years;we’ve started The Hoiggs: why? where?

 Oct’92 --------- Feb’96  “Run I” • 4 mile circ. superconducting ring • 6x6 proton anti-proton bunches • 3.5 us / crossing • 1.8 TeV cm energy • 1030-1031 inst.luminosity Run I tot. integrated luminosity: ~ 120-1 pb/detector

Zzzz Physics processes @ Tevatron Looks “interesting”…

lep Need much luminosity (x25 ~ top; mH=120) SM Higgs production @ Tevatron • Dominant processes @s=2TeV: Gluon fusion Higgsstrahlung Vector boson fusion Larger x-sect with new physics?

For M(H)< ~130 GeV • dominates • For M(H)> ~130 GeV • contributes • But cross-sect ¼ of • at MH~120 GeV • Need x100 more Lum ~ t-tbar lep SM Hoiggs decays

Standard Model channels M(H) < 130 GeV Run I searches: WH ZH SM Hoiggs signatures b-tagging and Mbb resolution are critical for a ligth Higgs

Silicon Vertex Detector Tevatron Run I Detectors

b do Lxy y z x b e,µ (in jets) B-tagging in Run I • Displaced verticest(b)~1.5 ps  Lxy(b) ~O(mm) CDF Silicon Vertex Detector (SVX) 1 vertex =< 2 tracks Lxy/sLxy > 3.0 sLxy ~ 100µ e(b-tag) ~ 25%/b-jet (~4% c-jet) e(b-tag) ~ 45%/event w/ 2b’s e(b-tag) ~ 0.2%/jet • Semileptonic b decays CDF/D0 e(b-tag) ~ 7%/b-jet e(b-tag) ~ 16%/event w/ 2b’s e(b-tag) ~ 0.5%/jet

Run I Mass Resolution Specific b-jet corrections Can see

CDF • Event selection: • High Pt + central • Pt(lep)>~20 GeV, Met>20, Pt(j)>15, eta<2 • + b-tags Backgrounds: Wbb, tt, WZ, tb D0

Event selection: • Multi-jet trigger: sum(Et)>125 GeV; 4-jets • + 2 b-tags • Pt(b,b)> 50 GeV • Need good M(bb) mass resolution Backgrounds: QCD, tt, Zjj, W/Zbb

Backgrounds: QCD, Zbb, ZZ, tt, tb • Event selection: • Met > 40 GeV • Veto isolated leptons/tracks • Et(j) > 15 GeV (2 or 3) • Df(Met,j) > 1.0 • Df (j1,j2) < 150o • + b-tags

Backgrounds: Zbb, ZZ, tt, tb • Event selection: • Pt(lep) > 420 GeV • 76<M(l,l)<106 GeV • Pt(j) > 15 GeV, eta<2 • Met < 50 GeV (veto top) • + 1 b-tag

Run I Higgs Limits D0 • SM Higgs limits: • Production x Branching Ratio • 95% CL about 30 times higher than SM prediction (for MH~115 GeV) • Sets the scale for needed Luminosity, si? • Best limit from HZbbnn channel but due to observed data • Expected best channels are: HZbbnn and HWbbln cdf

Higgs “candidate” Top candidate CDF tagged events

MSSM Higgs Searches • In the MSSM scenario: • Two Higgs doublets lead to 5 Higgs particles: • Two neutral CP-even: ho,Ho • One neutral CP-odd: Ao • Two charged: H+ ,H- • Masses governed by two parameters, for ex: • Tree level mass relations: • M(ho)<M(Zo)<M(Ho) • M(Ao)<M(Ho) • M(H+)<M(W) • But M(ho)<~130GeV after radiative corrections (top,stop etc.) ~130GeV

MSSM Higgs production @ Tevatron • H/h/A can have SM-like x-sections at small tan b For processes such as HW and HZ • Some production processes such as: Hbb/Hbb/Abb can have large x-sections at large tan b !!! g ~ 1/cos(b) ~ tan(b)  = h,H,A

MSSM Higgs Branching Ratios A  = h H tan b = 5 For all practical purposes: bb ~ 90% tt ~ 10% tan b = 50

 = h,H,A Event selection: • 4- jets + ET>125 GeV trigger • ET cuts on jets m dependent •  3 b-tag (secvtx) • bb > 1.9 mh Backgrounds: QCD, Z/W+jets,tt mA

Regions where Charged H+iggs Searches If then competes with • Depending on tanb Search directly via: Using hadronic tau identification: tracking+calorimeter Look in e,mu + tau and in tau+jets+Met channels • Search indirectly via lepton disappearance in t-tbar events: • Dilepton & lepton+jet top events suppressed • Given t-tbar x-sect & {mH,tanb} how likely is it to have observed N events? •  exclusion regions in {mH,tanb}

Charged Higgs Results

Bosophilic/Fermiophobic Higgs • Some models with two (or more) Higgs doublets predict Ho couplings only to vector bosons, with Hgg to be dominant for low mass Higgs. Backgrounds: Mostly QCD D0 Event selection: • Isolated, high-Pt, central, photons • High-Pt jets/leptons/MET

Bosophilic Higgs Limits D0 CDF

Conclusions • Run I • Searches in all channels for MH < 130 GeV/c2 • No sensitivity to SM Higgs, but we looked anyway • No sign of new physics • Combine results to set limits on xBR • Detectors, backgrounds, taggers understood! • Good experience and baseline for Run II • Sensitivity to neutral MSSM Higgs sector for large tan • Excluded MSSM regions • Run II • Many, many, improvements • We have a chance! (see next talk)

Higgs Searches at the Tevatron: Run I