Search for BSM Higgs at Search for BSM Higgs at the Tevatron the Tevatron Anton Anastassov Anton Anastassov (Northwestern University) (Northwestern University) For the CDF and D For the CDF and D Ø Ø Collaborations Collaborations Aspen 2008 Winter Conference: "Revealing the Nature of Electroweak Symmetry Breaking" January 15, 2008
Search for BSM Higgs at the Tevatron. Anton Anastassov (Northwestern University) For the CDF and D Ø Collaborations. Aspen 2008 Winter Conference: "Revealing the Nature of Electroweak Symmetry Breaking" January 15, 2008. BSM Higgs Searches. - PowerPoint PPT Presentation
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Search for BSM Higgs at the Search for BSM Higgs at the TevatronTevatron
Anton AnastassovAnton Anastassov(Northwestern University)(Northwestern University)
For the CDF and DFor the CDF and DØØ Collaborations Collaborations
Aspen 2008 Winter Conference: "Revealing the Nature of Electroweak Symmetry Breaking"
January 15, 2008
January 15, 2008
Search for BSM Higgs at the Tevatron - Anton Anastassov 2
BSM Higgs Searches• Look for particles consistent with the expected
physical manifestation of extended Higgs models:– 2HDM, Higgs triplets– Add SUSY a range SUSY models– Little Higgs models– …anything that goes beyond the SM Higgs
• Production/final states may be:– Unique to the BSM models– Similar to SM, but with modified production
rate/BR’s
Many search possibilities, but… finite manpower the CDF and DØ programs concentrate on:• Modes/models seen as most promising at the
Tevatron• Final states that can be efficiently triggered on
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The Tevatron Collider and Detectors
CDF and D0:• General purpose detectors, axial and
forward-backward symmetric• Precision tracking (incl silicon detectors)• Hadronic and EM calorimeters• Muon chambers• TOF systems
Recorded more than 3 fb-1 / experimentof quality data
(results in this presentation use up to 1.8 fb-
1)
p p collisions at s 1.96 TeV
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Search for BSM Higgs at the Tevatron - Anton Anastassov 4
The tools of the searchesThe searches described in the
following rely on good particle identification:
• Electrons• Muons
• B-jets
• Photons
• Taus (hadronic decays)
•Very well understood•Use characteristic energy in the EM and HAD calorimeters; hits in the muon chambers ()•Easily accessible standard candles (Z, W)
(see J. Zhu’s presentation on EW results at the Tevatron)
•Displaced secondary vtx associated with the jet•Probability of tracks in the jet not originating from the IP•Soft leptons (e, ) in jets•Wealth of information apply multivariate techniques
(see Weiming Yao’s talk for detailed discussion)
•Energy deposition in the EM calorimeter
not associated with a track•Shower shape to discriminate against 0’s
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Tau Reconstruction (hadronic decays)Two-cone algorithm for
tracks and 0’s:– Common axis:
direction of a “seed” track Signal cone reconstruct Isolation annulus implement jet veto
Search for BSM Higgs at the Tevatron - Anton Anastassov 12
Neutral MSSM Higgs production
Higgs decays:– bb (~90%)
– (~9%)
Hbb Hgg
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Neutral MSSM Higgs
• For large tan h or H are almost mass degenerate with A, similar couplings
• The other one is SM-like, low-mass (m<135 GeV)
• Production and decays are affected by radiative corrections *
• The bb channel is more sensitive to these corrections (and therefore to the SUSY specific scenarios), while the channel is more robust
* M. Carena, S. Heinemeyer, G. Weiglein, and C.E.M. Wagner, Eur.Phys.J. C45 (2006) 797-814
9)1(
9
)1(
tan)()()(
22
2
bbSMAbbbbABRAbb
9)1(
tan),()(),(
2
2
bSMAggbbABRAggbb
b is a function of SUSY parameters
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Neutral MSSM Higgs Decaying to bb
• Look for associated production with b(b): suppress multi-jet backgrounds– Have to pay a price
• Require at least three b-tagged jets• Look for signal evidence in the mass
of the two highest-ET jets
Biggest challenge: predict bg, shape
• Apply mistag rates to bbj events to determine shape• Normalize (outside of signal region) to the observation• Check the predicted shape using MC multijet events
(flavor composition fixed to theoretical predictions)
• Use MC to get shapes and biases for different flavor composition
• Create 2D templates: di-jet mass vs mdifftag discriminating
variable (mdifftag = m1
tag+m2tag-m3
tag )
• 2D fit of mjj and mdifftag used to extract signal and
determines bg flavor composition
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Neutral MSSM Higgs Decaying to bb
Di-jet mass distribution of the two highest-ET jets
in the DØ search (triple b-tagged events)
The data are consistent with SM expectation.
Extracted limits (Lint=0.9 fb-1)
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