Journal Club

Seminar Room

Friday 28th of November, 2025

Hour: 11:00

Title: Electroweak ηw meson

Presented by: Maria Cristina Fiore

Ref: https://arxiv.org/abs/2408.07535

Abstract:

We argue that the Standard Model is accompanied by a new pseudo-scalar degree of freedom, ηw-meson, which cancels the topological susceptibility of the electroweak vacuum and gets its mass from this effect. The prediction is based on the analyticity properties of the Chern-Simons correlator combined with the basic features of gravity. Depending on the quality level of the U(1)B+L-symmetry, ηw emerges as a B+L pseudo-Goldstone boson or as a Stückelberg 2-form of the electroweak gauge redundancy. An intriguing scenario of the first category is the emergence of ηw in the form of the phase of a U(1)B+L-violating fermion condensate triggered by the instantons, somewhat similar to η′-meson in QCD. Regardless of its origin, the presence of ηw-meson in the theory appears to be a matter of consistency.

Hour: 11:30

Title: Flavour, Accidentally

Presented by: Chiara Giuliano

Ref: https://arxiv.org/abs/2510.03403

Abstract:

We propose a new class of flavour models in which the spurion which breaks Standard Model flavour symmetries transforms in a non-minimal representation. Hierarchies in fermion masses, which arise from multiple insertions of this spurion, may be generated in a technically natural, accidental manner, from a handful of untuned (1) elements in the UV. This relies explicitly on the non-Abelian nature of the symmetry, distinguishing it from standard Froggatt-Nielsen-like scenarios. The pattern of flavour violating operators at dimension-6 can radically differ from previously considered scenarios, and emphasises the need for a broad flavour programme across all generations.