Spontaneous Flavor Violation

In the Standard Model, Flavor-Changing Neutral Currents (FCNCs) are strongly suppressed by a combination of small Yukawa couplings, small CKM matrix elements, and the GIM mechanism. Precise measurements of these processes put tight constraints on the structure of new physics coupled to quarks. These constraints are typically avoided by assuming that new interactions are either “flavor-blind” or have a structure very similar to the standard model (thus inheriting some of the aforementioned protections). While these assumptions allow new physics at the TeV scale, they also necessitate that the new physics be coupled primarily to the heaviest generation of quarks, seriously limiting the phenomenology at high energy experiments.

The diagram leading to the SFV texture in one possible UV completion.

Recently, I’ve been working with Daniel Egana-Ugrinovic and Patrick Meade on understanding different classes of “flavor vacua”, i.e., the patterns of quark couplings in models of new physics. In doing so, we’ve engineered a new Ansatz called Spontaneous Flavor Violation (SFV). This setup allows new interactions with sizable couplings to light quarks while still being safe from stringent constraints on FCNCs. In the context of particular models, e.g., a model with a second Higgs doublet, this leads to a number of novel signatures at colliders such as dijet resonances and enhanced Yukawa couplings of the Standard Model Higgs. For more details, check out our recent paper, and some preliminary results presented at Pheno 2019.

Samuel Homiller
Post-Doctoral Fellow

Post-Doctoral Fellow in the HETG at Harvard University.


We examine a deep relationship between enhanced couplings of the Higgs to light quarks and the di-Higgs production process at the LHC.

We show that the observed events at the KOTO experiment can be explained by minimal models of light new physics.

We show that Higgses with large couplings to light quarks lead to interesting signals in dijets and enhanced Higgs Yukawas, and are …

We discuss flavor-aligned theories, which avoid bounds from Flavor-Changing Neutral Currents, and introduce the Spontaneous Flavor …


An introduction to the Spontaneous Flavor Violation Ansatz, and its application to a Two Higgs Doublet Model.