B-anomalies in a twin Pati-Salam theory of flavour including the 2022 LHCb R_K(*) analysis

Abstract

We perform a comprehensive phenomenological analysis of the twin Pati-Salam theory of flavour, focussing on the parameter space relevant for interpreting the B-anomalies via vector leptoquark U₁ exchange. This model provides a very predictive framework in which the U₁ couplings and the Yukawa couplings find a common origin via mixing of chiral quarks and leptons with vector-like fermions, providing a direct link between the B-anomalies and the fermion masses and mixing. We propose and study a simplified model with three vector-like fermion families, in the massless first family approximation, and show that the second and third family charged fermion masses and mixings and the B-anomalies can be simultaneously explained and related. The model has the proper flavour structure to be compatible with all low-energy observables, and leads to predictions in promising observables such as τ → 3μ, τ → μγ and B→K(*) vv at Belle II and LHCb. The model also predicts a rich spectrum of TeV scale gauge bosons and vector-like fermions, all accessible to the LHC. In this updated version we have included an extended analysis considering the new 2022 LHCb data on R_K(*), which has slightly shifted the preferred parameter space with respect to the 2021 case. The model can still explain the R_D(*) anomalies at 1σ in a narrow window, however we expect small deviations from the SM on the R_K(*) ratios, to be tested in the future via more precise measurements by the LHCb collaboration. We also predict R_D =R_D*, with future measurements shifting the world averages to slightly smaller central values.

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Identifiers

ORCID for Mario Fernández Navarro: orcid.org/0000-0002-8796-0172

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