# Presentation: 677765

## Higgs Searches at the Tevatron (Run I)

- Introduction
- SM Higgs
- ZH & WH with H  bb (CDF & D****)
- MSSM Higgs
- bb with =H0,h0,A0  (CDF)
- H+ (CDF & D****)
- Fermiophobic Higgs
- H  CDF & D****)
- Conclusions

- Lorenzo Moneta
- University of Geneva
- on behalf of
- CDF and D**** collaboration

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- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## 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

- Lorenzo Moneta

## Tevatron (Run I) 

- Tevatron (Run **I**)

- Run I   (Oct. 92  Feb. 96)
- total integrated luminosity
- 	~ 120-1 pb / detector

- 	_Tevatron _
- proton-antiproton collision @ s = 1.8 TeV

- Expected  ~ 2 fb-1 in Run IIa !

**CDF**

**DØ**

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## SM H0 production @ Tevatron

- SM H0 production @ Tevatron

- Gluon Fusion
- too difficult (QCD background)
- Higgsstrahlung
- 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 ??

- for M(H) = 120 Gev/c2
- with QCD NLO correction

- Vector Boson fusion
- radiation off heavy quark
- very small in the SM

-  = 0.70 pb

- ZH:   = 0.10 pb

- WH:  = 0.16 pb

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## 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 !  

- 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 !

- SM Higgs decays

- For M(H) = 120 GeV/c2

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## Tevatron Run I channels : (W/Z + H with M(H) < 130 GeV)

BG:  QCD multijets 

BG: 

BG: QCD,  

BG: 

- BG:  QCD multijets
- BG:
- BG: QCD,
- BG:

- SM H signatures (W /Z + H)

- _Essential for these analyses_:
-  b tagging
-  good di-jet mass resolution

- ( 50%  of W/Z H )

- (  9% )

- ( 5.4%)

- ( 1.8%)

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## b tagging at the Tevatron

- Techniques developed for top analyses. Two algorithms:
- Soft Lepton Tagging (SLT)    (CDF & DØ)
- semileptonic b decays:
- DØ:   ( pT > 4 GeV)    CDF:  & 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

- secondary vertex

- primary vertex

- b jet

- (b-tag) ~ 20%/b-jet
- (mistag) ~ 0.2%/jet

- (decay-length) ~ 100 m

- (b-tag)  ~ 7%/b-jet
- (mistag) ~ 0.5%/jet

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

##     Search for            

- Final states are lepton (e/) + MET + b’s
- Event selection:
- high pTlepton: pT(lep) > 20 GeV &  <1
- MET>20
- 2 jets with  ET(j)>15, <2
- b-tags  (single OR double jet tag)
- Backgrounds:
- Results (CDF & D****) 106 pb-1

- CDF

- mbb

- 1 b-tag

- 2 b-tags

- 95% CL Limit on BR:
- 26-28 pb for 90<MH<130 (CDF)
- 40-19 pb for 90<MH<120 (D****)

- from fit to di-jets mass:

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

##      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
-  (MET,j) > 60°  for all jets (ET>8)
-  (j1,j2) < 150°
- b-tags  (single OR double)
- Backgrounds:
- QCD and
- Results (88 pb-1)

- 95% CL Limit on BR:
- ~ 8 pb for 90<MH<130

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

##      Search for            

- 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, <2
- MET < 50 GeV  (against top di-lepton evts)
- 1 b-tag
- Backgrounds:
- Results (106 pb-1)

- 95% CL Limit on BR:
- 56-24 pb for 90<MH<130

- mbb

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

##   Search for            

- Multi-jet final state with b’s
- Event selection (CDF):
- Multi-jets trigger
-  4 jets with ET>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)

-  Need good Mbb resolution against background

- 95% CL Limit on BR:
- 30-16 pb for 90<MH<130

- mbb

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- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## Combined limit for SM Higgs

- CDF combination of
- 95 % CL limit on

- x 30 SM cross-section (mH = 115)
- Limit is dominated by bb
- Expected best limits from:
-  bb and lbb
- poor lbb limit due to a small excess in observed events
- Need more luminosity
-  RUN II

- limit = 7.4-8.2 pb
-  for mH = 90-130 GeV/c2

- LEP

- SM

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- Moriond QCD 17-23 March 2001

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## 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:   tan 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 tan
- enhanced to d-type quark and leptons
- suppressed to u-type quark

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## MSSM Higgs production 

- MSSM Higgs production

- Small tan
- SM-like cross-sections

- Large tan
- enhanced hbb coupling
- hbb/Hbb/Abb  can have large cross-sections ( tan****

- tan = 3

- tan = 30

- pb

- pb

- h

- H

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- H

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- Moriond QCD 17-23 March 2001

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##    Search for 

- Exploit enhanced Yukawa couplings  looking for bb production ( = h,HA)
- large cross sections ( tan
- 4-b’s jets final state
- Event selection (CDF):
- Multi-jets trigger
- 4 jets with (ET)>125 GeV & ET>15
- ET(j) cuts depending on m()
-  3 b-tags
-  (bb) > 109° (against gbb)
- Backgrounds:
- QCD (bb/cc), Z/Wjj, top

- CDF results (91 pb-1)

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- Moriond QCD 17-23 March 2001

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##   Limit for 

- Limit (95%CL for M = 100 GeV):
- convert BR limit in tan vs Higgs mass exclusion
- No mixing    &   Maximal Mixing for the stop

- Tevatron complements LEP !

- BR < 25.7 pb

- tan vs m(h)

- tan vs m(A)

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## 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 tan

- Direct Search (CDF):
- look for H+ in t-tbar evts
- BR(H+ ****1 for large tan****
- WHbb or HHbb channels in addition to WWbb
- look for l + ****+ MET + jj events (l = e,****,****)
- use **** identifications via hadronic decays (tracking + calorimeter)
- backgrounds:
- Z ****** ****** + jj, W+3 jets, WW/WZ
- acceptances for single and double H production

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## 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), tan
- given measured x-section  (when BR(t  H+b) = 0)
- 	exclusion regions in the
-  	m(H+)-tanplane

- New Exclusion regions at low and high tan

**LEP2 (ADLO)**

- D0** **

- Moriond QCD 17-23 March 2001

- Lorenzo Moneta

## Fermiophobic Higgs

- In some models Higgs couples only to vector bosons
- BR(H ) dominant for light Higgs (m(H) < 100)
- Searches for W/Z + H  jj
- D**** search:
- di-photons + jets
- Backgrounds from QCD
- fakes or real in jets
- CDF search
- di-photons with e/ + 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

- Lorenzo Moneta

## 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:
- bb search with sensitivity for high tan 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

- Lorenzo Moneta