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Phenomenology of the Singlet Extended Standard ModelPowerPoint Presentation

Phenomenology of the Singlet Extended Standard Model

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### Phenomenology of the Singlet Extended Standard Model

Mat McCaskey

with V. Barger, P. Langacker, M. Ramsey-Musolf, and G. Shaughnessy

Pheno2007

May 8th, 2007

SM Higgs + Scalar Singlet

Add one singlet to the Higgs potential

- Higgs is indistinguishable from SM
- Singlet is shifted so it obtains no VEV

-Singlet only couples to the Higgs

Two specific cases to study

Case 1: Singlet couples to the Higgs (O’Connell et al.)

Case 2: Impose reflection symmetry (McDonald & Burgess et al.)

Case 1: Higgs and Singlet Mixing

Higgs BF same as SM

Exception: mH2> 2mH1 then H2 H1 H1 is open

Higgs coupling reduced universally by mixing parameter

BF of H1 same as SM Higgs of equal mass

Case 2: Reflection Symmetry

- S-S symmetry prevents S decay
- DM candidate

- DM singlet annihilates through the Higgs boson via

Annihilation processes:

Case 2: Higgs decay to singlet

- Higgs decays to invisible states which reduces the rate of traditional modes.

Case 2: Finding invisible Higgs

- Weak boson fusion:
- Extract signal with cuts on azimuthal correlation of forward jets and large missing pT

- Z-Higgstrahlung:
- Cuts on di-lepton separation and invariant mass extract signal
- Combined model independent Higgs mass determination.

Eboli and Zeppenfeld

Davoudiasl, Han, Logan

Case 2: Relic Density

- Numerically solved Boltzman equation (McDonald et al., Gondolo et al., Kolb and Turner)

Case 2: Relic Density

- WMAP constrains the relic density to be between 0.099 < Sh2 < 0.123

Case 2: Scattering Cross Section

- Direct detection of the dark matter candidate by elastic scattering off a nucleus.

Case 2: Higgs discovery via stable S

- OPAL: Higgs w/SM couplings mh>82 GeV
- ATLAS reach on BF(Hinv.) to ~ 20%

Higgs can be discoverable through visible or invisible modes with early LHC data.

Summary

SM + 1 scalar singlet:

Case 1: Singlet Mixes with SM Higgs

-Traditional discovery modes weakened if

H2 H1 H1 is open

-Higgs discovery may be possible with new decay modes through new modes.

Case 2: Reflection Symmetry (Stable S)

-DM Candidate

-Visible discovery modes weakened from HSS.

-Higgs may be discoverable through invisible modes.

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