Göttingen 2025 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 3: Higgs Physics II (BSM Higgs)

T 3.6: Vortrag

Montag, 31. März 2025, 18:00–18:15, ZHG105

Seesaw mechanism in the Georgi-Machacek model — •Colin Heckmeyer¹, Heidi Rzehak², and Emilia Welte¹ — ¹Institut für theoretische Physik, Universität Tübingen — ²Physikalisches Institut, Universität Freiburg

The current experimental measurements of the Higgs properties conform so far with the Standard Model (SM), however allow also for a more complex Higgs sector than the SM one. This opens the door for various extensions, one of which is the Georgi-Machacek model (GM). This model includes a complex SU(2) Higgs triplet state, a real SU(2) Higgs triplet state, and a real SU(2) Higgs doublet state. It is particularly appealing because it allows for the introduction of a type II seesaw mechanism term, an interaction term between the complex triplet and the leptons, generating a mass term for neutrinos. In this model, the neutrinos are assumed to be Majorana particles.

In this talk, a model combining the GM and the seesaw mechanism is introduced. Within this model, the leading-order (LO) decay of an SM-like Higgs boson is presented. One of the key features of the GM is maintaining the rho parameter at unity at LO. The rho parameter is a conserved quantity of custodial symmetry. This symmetry, however is violated at next-to-leading order (NLO) and requires taking custodial symmetry violating terms at LO into account for a proper renormalization procedure. Using this approach, a NLO analysis of the decay of the SM-like Higgs boson is discussed.

Keywords: Higgs boson; Georgi-Machacek model; type II seesaw mechanism; Beyond the Standard Model; custodial symmetry