Oct 2021 - Sept 2022
# External Seminar by Neda Darvishi

→
Europe/London

Description

Title

**Classifying Accidental Symmetries in nHDM and Natural SM alignment Limit**

**Abstract:**

I will discuss classifying accidental symmetries in multi-Higgs

Doublet Models (nHDMs). The potentials of nHDMs contain a large number of

SU(2)_L-preserving accidental symmetries as subgroups of the symplectic

group Sp(2n). To classify these, prime invariants and irreducible

representations in bilinear field space can be used that enable us to

explicitly construct accidentally symmetric nHDM potentials. I will

showcase the classification of the symmetries and present the relationship

between the theoretical parameters of the scalar potential for; (i) the

Two Higgs Doublet Model (2HDM) and (ii) the Three Higgs Doublet Model

(3HDM). In this approach, I will present the maximum number of 13

accidental symmetries for the 2HDM potential and 40 accidental symmetries

for the 3HDM potential. Furthermore, I will present the complete set of

continuous maximal symmetries that the potential of 2HDM and 3HDM should

satisfy for the natural Standard Model (SM) alignment limit. As a result,

no large mass scales or fine-tuning is required for such alignment limit,

which still persists even if these symmetries were broken softly by

bilinear mass terms. In particular, the Maximal Symmetric nHDM (MS-nHDM)

can provide natural SM alignment whereas exhibiting quartic coupling

unification up to the Planck scale. I will show that the MS-nHDM are very

predictive extension of the SM governed only by a few BSM parameters that

they allow to determine the entire Higgs-mass spectrum of the model.

Zoom link: IPPP Seminars (Thursday at 2 pm UK time)

https://durhamuniversity.zoom.us/j/99420124988?pwd=ZEFLSDB3THJtaWZOTU54R25mT1NuZz09

Meeting ID: 994 2012 4988