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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/178800
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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COY, Rupert, et al. New physics in b→sℓℓ transitions at one loop. European Physical Journal C. 2020. Vol. 80, num. 52. ISSN 1434-6044. [consulted: 8 of June of 2026]. Available at: https://hdl.handle.net/2445/178800