With or without U(2)? Probing non-standard flavor and helicity structures in semileptonic B decays

• Published in: Physics letters. B Vol. 800; p. 135080
• Main Authors: Fuentes-Martín, Javier, Isidori, Gino, Pagès, Julie, Yamamoto, Kei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.01.2020; Elsevier
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2019.135080

Motivated by the recent hints of lepton flavor universality violation observed in semileptonic B decays, we analyze how to test flavor and helicity structures of the corresponding amplitudes in view of future data. We show that the general assumption that such non-standard effects are controlled by a U(2)q×U(2)ℓ flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic B decays. Future measurements of RD(⁎), RK(⁎), B(B¯c,u→ℓν¯), B(B¯→πℓν¯), B(B→πℓℓ¯), B(Bs,d→ℓℓ¯(′)), as well as various polarization asymmetries in B¯→D(⁎)τν¯ decays, will allow to prove or falsify this general hypothesis independently of its dynamical origin.