Semi-inclusive Lepton Flavor Universality ratio in $b\to s{\ell }^{+}{\ell }^{-}$ transitions

Abstract

We construct a semi-inclusive Lepton Flavour Universality (LFU) ratio, $R_{\Sigma }$, to test $\mu /e$ universality in $b\to s{\ell }^{+}{\ell }^{-}$ transitions at $e^{+}{e}^{-}$ $B$-meson factories. Combining different decay channels, this observable maximises the sensitivity to possible LFU violations of short distance origin, yet preserving a clean theoretical interpretation in case of a deviation from its Standard Model prediction, $R_{\Sigma }^{\mathrm{SM}}=1$.

5 pages, 1 figure