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New physics in b→sℓℓ transitions at one loop

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We investigate new-physics contributions to b→sℓℓ transitions in the context of an effective field theory extension of the Standard Model, including operator mixing at one loop. We identify the few scenarios where a single Wilson coefficient, C/Λ2∼1/TeV2, induces a substantial shift in the lepton flavour universality ratios RK and RK∗ at one loop, while evading Z-pole precision tests, collider bounds, and other flavour constraints. Novel fits to the present data are achieved by a left-handed current operator with quark-flavour indices (2, 2) or (3, 3). Interestingly, the running of the Standard Model Yukawa matrices gives the dominant effect for these scenarios. We match the favoured effective-theory scenarios to minimal, single-mediator models, which are subject to additional stringent constraints. Notably, we recognise three viable instances of a leptoquark with one coupling to fermions only. If the anomalies were confirmed, it appears that one-loop explanations have good prospects of being directly tested at the LHC.

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Società Italiana di Fisica & Springer Verlag

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European Physical Journal C, 2020, vol. 80, num. 52

# metadata.dc.source[].value
Articles publicats en revistes (Física Quàntica i Astrofísica)

# metadata.dc.title[].value
New physics in b→sℓℓ transitions at one loop