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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

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  • A SUSY Higgs Primer

  • Searching for hbb

  • Doubling your fun with H++

  • h  gg : Pushing beyond LEP

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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