Higgs bosons appear in theories with broken local gauge symmetries. In the Standard Model, Higgs is the last piece of the puzzle remaining to be discovered. Unification of the weak force and the electromagnetic force is achieved by Higgs coupling to the gauge bosons which have "weak" flavor, thereby giving it a large "effective" mass and reducing the range of the interaction, hence making the weak force "weak". This effective mass depends on the coupling between the particle and the massive Higgs boson. It can accommodate the masses of fundamental particles, which would otherwise be massless due to the underlying symmetry of the Standard Model (SM).
There is abundant evidence that the
Higgs particle in the Standard
Model is light. Consistency of the standard model places some loose
bounds on the range of the Higgs mass possible from theory. Direct
searches from LEP 2 experiments places the lower limit on the Higgs
mass at MH>114 GeV. Indirect evidence from fits to
the electroweak observables points to the preferred mass of the Higgs
at 87+36-27 GeV
at 68% C.L. However, the sensitivity isn't great and the 95% C.L. upper
limit is 160 GeV (without LEP 2 direct search limit), or
190 GeV (including this limit). Plot to the left shows the
expected reach of the Tevatron.
In general, Higgs particles arrise in any model
with a broken local
gauge symmetry. In models extending the Standard Model, there can be
more than one Higgs particle and it is possible that in these models
none of them behaves like the Higgs in the SM.
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SM Higgs searchesInteresting channels are WH and ZH, where leptonic decays of W/Z and H decays to two b-jets provide handles against the more copious SM background. For higher mass we are looking at H→WW. |
Exotic Higgs searchesDoubly charged Higgs bosons (H++,H--) are predicted by some beyond the SM models with Higgs triplets, we can look for these in like-signed lepton final states. In some models with reduced coupling to fermions, Higgs decays to two photons (H→γγ) can be enhanced. |
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W/Z+jets measurements These are important physics and instrumental backgrounds to Higgs searches at the Tevatron. Even with NLO calculations, these are predicted with large theoretical uncertainties. We are going to measure W/Z+ jets, with and without b-tagging. |
Search for MSSM Higgs There are 2 Higgs doublets in the mimimal supersymmetric standard model (MSSM), which couple to particles of different weak isospin. Coupling to down-type quarks and leptons (such as τ) can be significantly enhanced in large tan β parameter space of the model. |
