TypeIISeesaw: Canonical type II seesaw at NLO in QCD

Contact information

Implementation author: Benjamin Fuks

• LPTHE / Sorbonne U.
• fuks@…

In collaboration with Miha Nemevšek and Richard Ruiz. See ​arXiv:1911.NNNNN [hep-ph].

Model Description

We extend the Standard Model by adding a scalar field lying in the adjoint representation of the weak groupe Δ with an hypercharge equals to 1. After electroweak symmetry breaking, this gives rise to one extra CP-even scalar Higgs Δ⁰, one charged scalar Δ^± and one doubly-charged scalar Δ^±± that are mostly of a triplet nature. The corresponding Lagrangian reads

\begin{equation}
  \mathcal{L} = \mathcal{L}_{\rm SM} +  {\rm Tr}\big[D_\mu \hat\Delta^\dag D^\mu\hat\Delta\big] - V_\Delta + \mathcal{L}_{{\rm Y}_\Delta}
\end{equation}

where the extra terms respectively represents the gauge-invariant kinetic terms for the triplet, the extra pieces to the scalar potential and the Yukawa interactions giving rise to neutrino masses. The above Lagrangian was implemented in the Feynman Gauge into FeynRules 2.3.35. QCD renormalization and R2 rational counter terms were determined using MoGRe v1.1, NLOCT v1.02 and FeynArts 3.9. Feynman rules were collected into a single UFO, available below. In the UFO file, five massless quarks are assumed as are zero off-diagonal CKM matrix entries. These additions permit tree-level calculations at LO and NLO in QCD and loop-induced calculations at LO in QCD using MadGraph_aMC@NLO.