Closing the window on single leptoquark solutions to the B-physics anomalies

Authors

A. Angelescu, University of Nebraska - LincolnFollow
D. Becirevic, Universite Paris-SaclayFollow
D. A. Faroughy, J. Stefan InstituteFollow
O. Sumensari, Istituto Nazionale Fisica Nucleare, Sezione di PadovaFollow

Date of this Version

2018

Citation

JHEP10(2018)183

Comments

© The Authors.

Open access

https://doi.org/10.1007/JHEP10(2018)183

Abstract

We examine various scenarios in which the Standard Model is extended by a light leptoquark state to solve for one or both B-physics anomalies, viz. R_D(◦)^exp > R_D(◦)^SM or/and R_K(◦)^exp < R_K(◦)^SM. To do so we combine the constraints arising both from the low-energy observables and from direct searches at the LHC. We find that none of the scalar leptoquarks of mass m_LQ ≃ 1 TeV can alone accommodate the above mentioned anomalies. The only single leptoquark scenario which can provide a viable solution for m_LQ ≃ 1÷2 TeV is a vector leptoquark, known as U1, which we re-examine in its minimal form (letting only left-handed couplings to have non-zero values). We find that the limits deduced from direct searches are complementary to the low-energy physics constraints. In particular, we find a rather stable lower bound on the lepton flavor violating b → sℓ_1^±ℓ_2^± modes, such as B(B → K μΤ). Improving the experimental upper bound on B(B → K μΤ) by two orders of magnitude could compromise the viability of the minimal U₁ model as well.