Implications of the discovery of a Higgs triplet on electroweak right-handed neutrinos

Abstract

Electroweak scale active right-handed neutrinos such as those proposed in a recent model necessitate the enlargement of the SM Higgs sector to include Higgs triplets with doubly charged scalars. The search for and constraints on such Higgs sector has implications not only on the nature of the electroweak symmetry breaking but also on the possibility of testing the seesaw mechanism at colliders such as the LHC and the ILC.

On neutrino and charged lepton masses and mixings: a view from the electroweak-scale right-handed neutrino model

“…As noticed in [11][12][13][14][15], the positive contribution to the S-parameter coming from the extra right-handed mirror quark and lepton doublets could be partially cancelled by the negative contribution coming from the triplet Higgs fields. Ref.…”

“…One of us (PQH) has proposed a model [11][12][13][14][15] of electroweak-scale right-handed neutrinos in which (as we will briefly review below) ν R 's belong to SU(2) doublets along with mirror charged leptons. This has two distinct advantages: 1) ν R 's are non-sterile and couple to the Z and W bosons; 2) Since ν R 's are members of doublets, a Majorana mass term necessarily comes from the vacuum expectation value (VEV) of a triplet Higgs field which spontaneously breaks SU(2) × U(1) Y (in addition to the Higgs doublet) and, as a result, M R ∝ O(Λ EW ).…”

“…The EW ν R model [11][12][13][14][15] keeps the same gauge group as the SM i.e. SU(3) C ×SU(2)× U(1) Y but increases its fermion as well as its Higgs content, all of which are listed below.…”

“…In the original version [11][12][13][14][15], this Higgs doublet couples to both SM and mirror fermions. An extended version was proposed [16] in order to accommodate the 125-GeV SM-like scalar and, in this version, Φ 2 only couples to SM fermions while another doublet Φ 2M whose VEV is φ 0 2M = v 2M / √ 2 couples only to mirror fermions.…”

“…The phenomenology of mirror quarks and leptons was briefly discussed in [11][12][13][14][15] and a detailed analysis of mirror quarks will be presented in [24]. It suffices to mention here that mirror fermions decay into SM fermions through the process q M → qφ S , l M → lφ S with φ S "appearing" as missing energy in the detector.…”