Abstract

Abstract A heavy Standard Model Higgs boson is not only disfavored by electroweak precision observables but is also excluded by direct searches at the 7 TeV LHC for a wide range of masses. Here, we examine scenarios where a heavy Higgs boson can be made consistent with both the indirect constraints and the direct null searches by adding only one new particle beyond the Standard Model. This new particle should be a weak multiplet in order to have additional contributions to the oblique parameters. If it is a color singlet, we find that a heavy Higgs with an intermediate mass of 200–300 GeV can decay into the new states, suppressing the branching ratios for the standard model modes, and thus hiding a heavy Higgs at the LHC. If the new particle is also charged under QCD, the Higgs production cross section from gluon fusion can be reduced significantly due to the new colored particle one-loop contribution. Current collider constraints on the new particles allow for viable parameter space to exist in order to hide a heavy Higgs boson. We categorize the general signatures of these new particles, identify favored regions of their parameter space and point out that discovering or excluding them at the LHC can provide important in- direct information for a heavy Higgs. Finally, for a very heavy Higgs boson, beyond the search limit at the 7 TeV LHC, we discuss three additional scenarios where models would be consistent with electroweak precision tests: including an additional vector-like fermion mixing with the top quark, adding another U(1) gauge boson and modifying triple-gauge boson couplings.

Highlights

  • From the viewpoint of simplicity, the Higgs mechanism is an economical way to provide the W and Z gauge boson masses as well as fermion masses in the SM

  • If the new particle is charged under QCD, the Higgs production cross section from gluon fusion can be reduced significantly due to the new colored particle one-loop contribution

  • For a very heavy Higgs boson, beyond the search limit at the 7 TeV LHC, we discuss three additional scenarios where models would be consistent with electroweak precision tests: including an additional vector-like fermion mixing with the top quark, adding another U(1) gauge boson and modifying triple-gauge boson couplings

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Summary

Oblique parameter analysis

A more proper attitude towards a heavy Higgs boson around or above 200 GeV is to include additional new heavier particles in the EWPT. The constraints from fitting the T parameter can not set a constraint on the absolute mass scales By requiring those particles to modify the Higgs decays or production cross sections, one can fix the masses of those particles and have a pretty concrete prediction for the LHC. This kind of prediction is only possible due to our simplicity assumption that only one new particle is relevant for both EWPT and Higgs phenomenologies

Hiding a heavy Higgs using a new color-singlet particle
Scalar doublet
Scalar triplet
Collider phenomenologies
Decays of scalars
Higgs decays
Direct collider searches
QCD charged scalars
Modifications on the Higgs boson production
The properties of the colored particles
The collider constraints and signatures of colored states
Fermions
Non-linearly realized EWSB
Conclusions and discussion
Findings
A Higgs couplings to two gluons and two photons
Full Text
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