Abstract
Abstract Motivated by recent results from Higgs searches at the Large Hadron Collider, we consider possibilities to enhance the diphoton decay width of the Higgs boson over the Standard Model expectation, without modifying either its production rate or the partial widths in the WW and ZZ channels. Studying effects of new charged scalars, fermions and vector bosons, we find that significant variations in the diphoton width may be possible if the new particles have light masses of the order of a few hundred GeV and sizeable couplings to the Higgs boson. Such couplings could arise naturally if there is large mass mixing between two charged particles that is induced by the Higgs vacuum expectation value. In addition, there is generically also a shift in the Zγ partial width, which in the case of new vector bosons tends to be of similar magnitude as the shift in the diphoton partial width, but smaller in other cases. Therefore simultaneous measurements in these two channels could reveal properties of new charged particles at the electroweak scale.
Highlights
The LHC experiments, on the other hand, have sensitivity for Higgs bosons produced in gluon fusion and decaying into weak gauge bosons, for Higgs masses from about 120 GeV up to a mass close to 600 GeV
Studying effects of new charged scalars, fermions and vector bosons, we find that significant variations in the diphoton width may be possible if the new particles have light masses of the order of a few hundred GeV and sizeable couplings to the Higgs boson
We show the modifications in the Zγ partial width of the Higgs boson and the corresponding enhancements in the diphoton width
Summary
In the SM the leading contribution to the Higgs coupling to diphoton is the W ± boson loop, which is at least four times larger than the next-to-leading contribution from the top quark loop. We begin by re-writing the diphoton decay width in terms of the Higgs coupling to the particles in the loop: Γ(h γγ). An enhancement of the diphoton coupling to the Higgs may be obtained in this case, since the contribution of the off-diagonal term has the same sign as the leading SM contribution from the W loop. The reason for the different pattern between scalar and fermion is due the fact that they have opposite sign in the super-trace in eq (2.15) while in the QED one-loop beta functions they have the same sign From this argument it is easy to see that a four-generation lepton has the tendency to reduce the diphoton decay width, since it only worsens the SM top quadratic divergence in the Higgs mass
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