New physics in $b\to s\ell\ell$ transitions at one loop Auteur(s): Coy R., Frigerio M., Mescia Federico, Sumensari Olcyr (Article) Publié: -Eur.phys.j.c, vol. 80 p.52 (2020) Texte intégral en Openaccess : Ref HAL: hal-02340141_v1 Ref Arxiv: 1909.08567 Ref INSPIRE: 1754713 DOI: 10.1140/epjc/s10052-019-7581-y WoS: WOS:000523449400003 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 7 Citations Résumé: We investigate new-physics contributions to $b\rightarrow s \ell \ell$ 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, $C/\Lambda ^2 \sim 1/\mathrm{TeV}^2$, induces a substantial shift in the lepton flavour universality ratios $R_K$ and $R_{K^*}$ 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.