Higgs Searches at the Tevatron: Run I

J. Konigsberg / La Thuile, March 2001

1

CDF

D0

Ho

Higgs Searches at the Tevatron: Run I

Introduction The Higgs Run I

SM Higgs (CDF/D0)

ZHo & WHo

MSSM Higgs bbHo,ho,Ao

(CDF)

H+ (CDF/D0)

More beyond Bosophilic (CDF/D0)

Conclusions

Jacobo Konigsberg / Univ. of Florida / CDF


2

The Hoiggs: why? where?

[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 HiggsMHiggs < 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


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“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

Oct’92 --------- Feb’96

Run I tot. integrated luminosity: ~ 120-1

pb/detector


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Physics processes @ Tevatron

Zzzz

Looks “interesting”…


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SM Higgs production @ Tevatron

Dominant processes @s=2TeV:

Gluon fusion Higgsstrahlung

Vector boson fusion

)! (QCD ..difficult. toois Hgg mass) inv. met, (lept, y...possibilit a are / HZW

Need much luminosity (x25 ~ top; mH=120)

Larger x-sect with new physics?

tt

lep


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SM Hoiggs decays

lep

For M(H)< ~130 GeV> dominatesbbH

For M(H)> ~130 GeV> contributes

> But cross-sect ¼ of at MH~120 GeV

> Need x100 more Lum ~ t-tbar

WWHbbH


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SM Hoiggs signatures

Standard Model channels M(H) < 130 GeV

Run I searches:

>

>

>

>

bbHWpp 0

bbqqHZWpp 0/

bbHZpp 0

bbHZpp 0

ZH

WH

qq

qq

,e

ee

bb

bb

b-tagging and Mbb resolution are critical for a ligth Higgs


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Tevatron Run I Detectors

Silicon Vertex Detector


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B-tagging in Run I

Displaced vertices (b)~1.5 ps Lxy(b) ~O(mm)

Silicon Vertex Detector (SVX)1 vertex =< 2 tracks Lxy/Lxy > 3.0 Lxy ~ 100µ

(b-tag) ~ 45%/event w/ 2b’s

(b-tag) ~ 0.2%/jetx

y

z

Lxy

bdo

b e,µ (in jets)

Semileptonic b decays

20% ~ BR

20% ~ BR

Xvlcb

Xvlb

(b-tag) ~ 7%/b-jet

(b-tag) ~ 0.5%/jet

(b-tag) ~ 25%/b-jet (~4% c-jet)

(b-tag) ~ 16%/event w/ 2b’s

CDF

CDF/D0


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Run I Mass Resolution

Specific b-jet correctionsCan see bbZ

jjm


11

bbWH 0

Event selection:

> High Pt + central Pt(lep)>~20 GeV, Met>20, Pt(j)>15, eta<2

> + b-tags

q

*W0H

b

b

q WBackgrounds:Wbb, tt, WZ, tb

Exp. channelbcknd

dataBr x accept.(90<m(H)<130)

CDF 1 b-tag30 (5)

36 ~ 0.6 – 0.8 %

CDF2 b-tags

3 (1) 6 ~ 0.2 – 0.3 %

D0 1 b-tag25 (3)

27 ‘’

bbm

CDF

D0

bbm


12

bbqqHZW '0/

q*/* ZW 0H

q

q

b

b

q ZW / Backgrounds:QCD, tt, Zjj, W/Zbb

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

Exp. channelbcknd


CDF 2 b-tag ~600 589 1.5 – 2.9 %bbm


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bbZH 0

Exp. channelbcknd


CDF 1 b-tag39 (4)

40 ~ 0.5 – 0.8 %

CDF2 b-tags

4 (1) 4 ~ 0.4 – 0.5 %

bbm

Backgrounds:QCD, Zbb, ZZ, tt, tb

Event selection:> Met > 40 GeV> Veto isolated leptons/tracks> Et(j) > 15 GeV (2 or 3) (Met,j) > 1.0 (j1,j2) < 150o

> + b-tags

q

*0Z

0Z0H

b

b

q

bjm


14

bbZH 0

q

*0Z

0Z0H

b

b

q

Backgrounds:Zbb, ZZ, tt, tb

Exp. channelbcknd


CDF 1 b-tag 3 (1) 5 ~0.2 %

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

bbm


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Run I Higgs Limits

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 HZbb channel but due to observed data> Expected best channels are: HZbb and HWbbl

cdf

D0


16

CDF tagged events

bbpp ,

Higgs “candidate”

bbWWtt ,

Top candidate


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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)<~130 GeV after radiative corrections (top,stop etc.)

tan,Am~130 GeV


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MSSM Higgs production @ Tevatron

H/h/A can have SM-like x-sections at small tan

For processes such as HW and HZ

Some production processes such as:Hbb/Hbb/Abb

can have large x-sections

at large tan

SMHgg

WH SM

= h,H,A

)()()(2,,

SM

HAhHbbppbgbbpp

g ~ 1/cos() ~ tan()


19

AHh

MSSM Higgs Branching Ratios

For all practical purposes:bb ~ 90%~ 10%

tan

tan

=


20

bbbbbbpp

mA

mh

Event selection:

> 4- jets + ET>125 GeV trigger

ET cuts on jets m dependent

3 b-tag (secvtx) bb > 1.9

Backgrounds:QCD, Z/W+jets,tt

Exp. channelbcknd

data

Br x accept.(70<m(H)<300)

CDF 3 b-tag

21 (5)

20 ~ 0.2 – 0.6 %

= h,H,A


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Charged H+iggs Searches

Search directly via:

If then competes with > Depending on tan

btHmmm bHt

Wbt

Search indirectly via lepton disappearance in t-tbar events:• Dilepton & lepton+jet top events suppressed Given t-tbar x-sect & {mH,tan} how likely is it to have observed N events? exclusion regions in {mH,tan}

Regions where

Using hadronic tauidentification: tracking+calorimeterLook in e,mu + tau and in tau+jets+Met channels

tan

Hm


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Charged Higgs Results


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Bosophilic/Fermiophobic Higgs

Some models with two (or more) Higgs doublets predict Ho couplings only to vector bosons, with Hto be dominant for low mass Higgs.

q*/* ZW 0H

q ZW /

x

x

ExpChannel

xxbcknd data

Br x accept.(90<m(H)<130)

CDFe/ + MET

.or. qq6 (2) 6 ???

D0 qq 6 (2) 4 ‘’

Event selection:> Isolated, high-Pt, central,

photons> High-Pt jets/leptons/MET

Backgrounds:Mostly QCD

D0

m

jjm


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Bosophilic Higgs Limits

D0 CDF


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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)

Documents

Higgs Searches at the Tevatron: Run I