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Event Number 2914
Tuesday, February 12th, 2013
 Theory Seminar (High Energy/Cosmology)
 Higgs to diphoton decay with new vector fermions
 Time: 4:00 pm
 Place: 5280 Chamberlin Hall
 Speaker: Pedro Schwaller, Argonne National Laboratory
 Abstract: The discovery of the Higgs boson opens the possibility to probe new physics scenarios by analyzing Higgs production and decay rates. The loop induced decay to photon pairs is particularly sensitive to new physics contributions, and a possible enhanced rate for this decay has generated some interest in models that can explain it. I will present an extension of the SM with a family of vectorlike leptons. Not only can this model explain an enhanced diphoton decay rate of the Higgs, but it also provides a dark matter candidate while being in agreement with electroweak precision constraints. The necessarily large Yukawa couplings affect the running of the Higgs self coupling, such that an ultra violet (UV) completion is needed below the 10 TeV scale. A promising solution is to embed the model into a supersymmetric grand unified theory. Using RGEs upper bounds on the lepton Yukawa couplings can be derived, which limits the possible enhancement of the diphoton rate. Additional enhancement can be obtained if also the new sleptons are light, and I explore the parameter regions that are compatible with GUTscale vacuum stability, LEP limits and electroweak precision constraints.
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