Test of lepton universality with ${\Lambda }_b^0\to p{K}^{-}{\ell }^{+}{\ell }^{-}$ decays

LHCb collaboration, R. Aaij, C. Abellán Beteta +904

The ratio of branching fractions of the decays ${\Lambda }_b^0\to p{K}^{-}{e}^{+}{e}^{-}$ and ${\Lambda }_b^0\to p{K}^{-}{\mu }^{+}{\mu }^{-}$, $R_{pK}^{-1}$, is measured for the first time using proton-proto…