Reading the footprints of the B-meson flavor anomalies
Abstract
Motivated by the recent LHCb announcement of a 3.1σ violation of lepton- flavor universality in the ratio RK = Γ(B → Kμ+μ−)/Γ(B → Ke+e−), we present an updated, comprehensive analysis of the flavor anomalies seen in both neutral-current (b → sℓ+ℓ−) and charged-current (b → cτ ν ¯) decays of B mesons. Our study starts from a model-independent effective field-theory approach and then considers both a simplified model and a UV-complete extension of the Standard Model featuring a vector leptoquark U1 as the main mediator of the anomalies. We show that the new LHCb data corroborate the emerging pattern of a new, predominantly left-handed, semileptonic current-current interaction with a flavor structure respecting a (minimally) broken U(2)5 flavor symmetry. New aspects of our analysis include a combined analysis of the semileptonic operators involving tau leptons, including in particular the important constraint from Bs-B¯s mixing, a systematic study of the effects of right-handed leptoquark couplings and of deviations from minimal flavor-symmetry breaking, a detailed analysis of various rare B-decay modes which would provide smoking-gun signatures of this non-standard framework (LFV decays, di-tau modes, and B → K(*)ν ν ¯), and finally an updated analysis of collider bounds on the leptoquark mass and couplings.
- Publication:
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Journal of High Energy Physics
- Pub Date:
- August 2021
- DOI:
- 10.1007/JHEP08(2021)050
- arXiv:
- arXiv:2103.16558
- Bibcode:
- 2021JHEP...08..050C
- Keywords:
-
- Beyond Standard Model;
- Heavy Quark Physics;
- High Energy Physics - Phenomenology
- E-Print:
- 43 pages, 14 figures, 4 tables. v2: new appendix, matching the journal version