Particle Seminar

Monday, January 14, 2019

Speaker: Ben Keeshan

Time: 2:30PM -- 3:30PM

Location: HP4351

Title: Custodial Symmetry Violation in the Georgi-Machacek model

Abstract: I will discuss how custodial symmetry violation can be incorporated into the Georgi-Machacek (GM) model. The GM model adds isospin-triplet scalars to the Standard Model in a way that preserves custodial symmetry at tree level; however, this custodial symmetry has long been known to be violated at the one-loop level by hypercharge interactions. If we consider the custodial-symmetric GM model as arising at some high scale due to an unspecified ultraviolet completion, we can use the RGEs quantify the custodial symmetry violation induced as the model is run down to the weak scale. The measured value of the electroweak rho parameter (along with unitarity considerations) allows us to constrain the scale of the ultraviolet completion and the size of the custodial-symmetry-violating effects. I will present the constraints on the allowed scales of UV completion and the maximum custodial-symmetry violating effects in a parameter scan of a benchmark scenario and compare them to results from general parameter scans.