PHYS08200604017 Manimala Mitra - Homi Bhabha National Institute

artifact of the imposed µ-τ symmetry. In section 3.4, we study the cross-section for the
heavy fermion production at LHC, as a function of the fermion mass. In section 3.5, we
study the decay rates of these heavy fermions into the standard model leptons, Higgs
and gauge bosons. We compare and contrast our model against the usual type-III seesaw
models with only one Higgs. We also show the consequences of non-trivial mixing of the
heavy fermions on the flavor structure of their decays. In section 3.6, we discuss the
decay rates and branching ratios of the Higgs decays. We probe issues on Higgs decays,
which are specific and unique to our model. Section 3.7 is devoted to the discussion of
displaced decay vertices as a result of the very long living h 0 in our model. In section
3.8, we list the different possible final state particles and their corresponding collider
signature channels which could be used to test our model. We calculate the effective
cross-sections for these channels at LHC. We highlight some of the channels with very
large effective cross-sections and discuss qualitatively the standard model backgrounds.
Finally, in section 3.9 we present our conclusions. Discussion of the scalar potential,
the Higgs mass spectrum and the constraints from neutrino data on the Higgs sector
is discussed in detail in Appendix A. The lepton-Higgs coupling vertices are listed in
Appendix B.1, the lepton-gauge coupling vertices are listed in Appendix B.2, and the
quark-Higgs coupling vertices are listed in Appendix B.3.
3.2 Yukawa Couplings and Lepton Masses and Mixing
Inthissectionwedescribe themodel. WeaddthreeSU(2)triplet fermionstothestandard
model particle content. These fermions belong to the adjoint representation of SU(2).
They are assigned hypercharge Y = 0 and are self-conjugate. In the Cartesian basis the
triplet is
⎛ ⎞
Ψ i =
⎝ Σ1 i
Σ 2 i
Σ 3 i
⎠, (3.2)
where i = 1,2,3 and Ψ i = Ψ C i . In the compact 2×2 notation they will be represented
in our convention as
Σ i = √ 1 ∑
Σ j i ·σ j, (3.3)
2
j
where σ j are the Pauli matrices. The right-handed component of this multiplet in the
2×2 notation is then given by
( Σ
0
Σ Ri = Ri / √ )
2 Σ + Ri
Σ − Ri
−Σ 0 Ri /√ , (3.4)
2
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