On sum rules for semi-leptonic $b\to c$ and $b\to u$ decays

Wen-Feng Duan, Syuhei Iguro, Xin-Qiang Li +2

The semi-leptonic $b\to cl\nu$ processes are receiving a lot of attention, as the lepton flavor universality violation has been hinted by the measured ratios $R_{D^{(*)}} = Γ(B \t…