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

• DOI: 10.1016/j.physletb.2019.135080
• Publication Date: 2019-11-08T12:43:29Z
• Authors: Javier Fuentes-Ma...; Gino Isidori; Julie Pagès; Kei Yamamoto
• Keywords: Nuclear and High Energy Physics; High Energy Physics - Phenomenology; High Energy Physics - Phenomenology (hep-ph); 530 Physics; Physics; QC1-999; 0103 physical sciences; FOS: Physical sciences; 10192 Physics Institute; 3106 Nuclear and High Energy Physics; 01 natural sciences

12 pages, 4 figures (v2: very minor modifications)<br/>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 $U(2)_q \times U(2)_\ell$ flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic $B$ decays. Future measurements of $R_{D^{(*)}}$, $R_{K^{(*)}}$, ${\mathcal B}(\bar B_{c,u}\to \ell \bar ��)$, ${\mathcal B}(\bar B \to ��\ell \bar��)$, ${\mathcal B}(B \to ��\ell \bar\ell)$, ${\mathcal B}(B_{s,d}\to\ell\bar\ell^{(\prime)})$, as well as various polarization asymmetries in $\bar B\to D^{(*)} ��\bar ��$ decays, will allow to prove or falsify this general hypothesis independently of its dynamical origin.<br/>