Reading the footprints of the B-meson flavor anomalies

A bstract Motivated by the recent LHCb announcement of a 3 . 1 σ violation of lepton- flavor universality in the ratio R K = 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 → $$ c\tau \overline{\nu} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>cτ</mml:mi> <mml:mover> <mml:mi>ν</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> ) 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 U 1 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 B s - $$ {\overline{B}}_s $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>s</mml:mi> </mml:msub> </mml:math> 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 (*) $$ \nu \overline{\nu} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ν</mml:mi> <mml:mover> <mml:mi>ν</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> ), and finally an updated analysis of collider bounds on the leptoquark mass and couplings.

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