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Searches for Non-Minimal Higgs Bosons. Andre S. Turcot Brookhaven National Laboratory for the DØ Experiment at Fermilab. With many thanks to: A. Haas, A. Kharchilava and G. Watts. Outline. A SUSY Higgs Primer Searching for hbb Doubling your fun with H++

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Searches for Non-Minimal

Higgs Bosons

Andre S. Turcot

Brookhaven National Laboratory

for the

DØ Experiment at Fermilab

With many thanks to: A. Haas, A. Kharchilava and G. Watts



  • A SUSY Higgs Primer
  • Searching for hbb
  • Doubling your fun with H++
  • h  gg : Pushing beyond LEP

A SUSY Higgs Primer

  • Addition of a second scalar doublet results in 5 physical higgs bosons

h, H, A, H+, H-

  • Standard Model Yukawa couplings modified:
  • hbb : sin(b - a) - tanb cos (b – a)
  • Hbb:cos(b - a) + tanb sin(b – a)
  • Abb: tan b
  • Two interesting cases arise for large tan b
  • CP Even states can flip-flop playing the role of SM higgs
  • M(A) >> M(Z)  cos(b - a) << 1
  • M(A) ~ M(H), Hbb coupling  tan b
  • M(A) <~ M(Z)  cos(b - a) ~1
  • M(A) ~ M(h), hbb coupling  tanb

SUSY Higgs Production

  • When tan b is large two of the three
  • Neutral Higgs bosons will have enhanced bb couplings

CP-odd HiggsProduction

CP-even HiggsProduction


SUSY Higgs: The RunII Angle

  • Much theoretical progress since RunII SUSY-Higgs Wkshp
  • Recent work indicates that the LO cross-sections are an underestimate by a factor ~3 (e.g. hep-ph/0204093)
  • Better understanding of NLO effects, scale dependencies
  • Theoretical bias towards expecting large tan 
    • b-τ Yukawa unification at the GUT scale

→ mt/mb ~ tan  ~ 50

  • Since cross section scales astan2there will be a huge enhancement, O(1000) for motivated values
  • Leads to an interesting complementarity with LEP as Tevatron can probe high tan bregion of parameter space where small sin(b - a) and/or kinematics preclude hA, HA, Zh ZH production at LEP

Triggering on bb(h,H,A):

  • Multi-Level Trigger:
    • Level 1: Require 3 trigger towers of 5 GeV
    • Level 2: Require 3 jets of 8 GeV, HT > 50 GeV
    • Level 3: 3 Jets 15 GeV, 2 of 25 GeV, primary vtx within SMT
    • Rates at L ~ 60E30 are 280/100/6 Hz

Done for all trigger components

  • Efficiencies relative to off-line selection are excellent

e.g. for M=120 4 jets of 45, 35, 2x15 GeV (0.5 cone algorithm)

tagging b jets
Tagging b-jets

Secondary Vertex Tag


Extra Loose Operating Point

Light j ~ 2%

Many improvements

in the works

Improved Tracking

Improved Alignment

Improved Algorithms


This represents only the first “sketches” in the art of b-tagging


Search for bb(h,H,A):

Leading Backgrounds:

jjjj with multiple fakes

bb jj with fake (8% ccjj)

Zbb and bbbb are small

Comparison of double b-tagged events with ≥4 jets to Monte Carlo

The ALPGEN Monte Carlo describes the multi-jet heavy-flavor background very well.

We have measured the normalization factor of data / MC :


≥ 4 jets≥ 2 b-tags


Search for bb(h,H,A):

Comparison of triple b-tagged events to expected background

The background shape was extrapolated from double b-tagged data using a tag-rate-function derived on the full multi-jet data sample.

Limits were set on the signal production, using simulated signal shapes, the normalized background, and the observed data.

Excluded Signal

≥ 3 jets≥ 3 b-tags

systematic uncertainties
Systematic Uncertainties

Systematic Errors on Acceptance (%)

Dominated by JES: Ongoing efforts to improve

Systematic Errors on Backgrounds…

Both b-id related and statistics

8-11% depending upon the optimized point


Search for bb(h,H,A):

Constraints in the MSSM parameter space

Limits will continue to improve with:

More data

Better b-tagging

Better triggers

Expect new results soon!

131 pb-1 of data

Note Complementarity with LEP


Search for Doubly-Charged Higgs

Many models predict the existence of Higgs bosons with twice the electric charge of other particles:

  • Left/Right Symmetric
  • Higgs Triplet
  • Little Higgs

We search for decays of the doubly-charged Higgs into two like-signed muons.

Assume a 100% branching ratio to muons when setting limits

Coupling depends on L/Rhandedness

Feynman diagram for the production of doubly-charged Higgs


Search for Doubly-Charged Higgs

Comparisons of mass and Δφ distributions of the di-muon data to Monte Carlo

Good agreement before requirment of Like Sign muons


Search for Doubly-Charged Higgs

Comparisons of mass and Δφdistributions of the like-signed and isolated di-muon data to Monte Carlo

No evidence of excess in like-sign isolated muons:

3 candidates vs 1.5 +/- 0.4 expected


Search for Doubly-Charged Higgs

Confidence Limit set as a function of doubly-charged (left-handed) Higgs mass

Set limits on the masses of doubly-charged Higgs bosons:

mHL ++ > 118.4 GeV

mHR ++ > 98.2 GeV

113 pb-1

On going efforts to improve

Double the data set

Include t t, WW channels


Search for Higgs→ γγ

Some models predict an enhanced branching fraction of Higgs bosons to two photons:

  • Top-color Higgs
  • Fermio-phobic Higgs

“Boso-phillic” at U of C

Total bkgd.



Error on BG

Reasonable agreement

with expected background

Di-photon Invariant mass


Search for Higgs → γγ

No evidence of excess

Set limits as a function

of branching ratio

assuming model dependent

production cross-section

Can extend LEP Reach

With current data but mass limits will require more data

Future Analyses will benefit from improved g ID



has searched for non-minimal Higgs bosons

  • Data sets of 113 to 195 /pb studied
    • Results on hbb, H++ and h  gg
  • Unfortunately with no hint of a signal
  • Improvments to all channels in progress Attacking the key issues, b-tagging, JES
  • Stay tuned for more exciting results