Explaining the hints for lepton flavour universality violation with three S 2 leptoquark generations

• Published in: The journal of high energy physics Vol. 2022; no. 6; pp. 1 - 44
• Main Authors: Andreas Crivellin, Benjamin Fuks, Luc Schnell
• Format: Journal Article
• Language: English
• Published: SpringerOpen 01.06.2022
• Subjects: Specific BSM Phenomenology; Theories of Flavour
• ISSN: 1029-8479
• DOI: 10.1007/JHEP06(2022)169

Abstract Leptoquarks are prime candidates for explaining the intriguing hints for lepton flavour universality violation. In particular, the SU(2) L doublet of scalar leptoquarks S 2 is capable of providing an explanation for the tensions between the measurements and the Standard Model predictions in (g − 2) μ , b → sℓ + ℓ − and b → cτν processes, as well as in non-resonant di-electron production. However, in the minimal setup with a single leptoquark generation, a common explanation for all these issues is not possible as this would lead to unacceptably large charged lepton flavour violation. We therefore propose a model with three generations of S 2, each coupling exclusively to a single lepton flavour, i.e. a model extending the Standard Model particle content by an electroquark, a muoquark and a tauquark. We show that after taking into account other constraints, such as those originating from electroweak precision observables and ∆F = 2 processes, it is possible to provide a combined explanation for all these hints of lepton flavour universality violation. Moreover, we find that the presence of the tauquark can generate a dimension-six O 9 U $$ {\mathcal{O}}_9^U $$ operator via off-shell photon penguin diagrams, which, together with the muoquark contribution, further improves the global fit to b → sℓ + ℓ − data.