New Probes of Electron-Muon Universality in B → Kℓ ⁺ℓ ⁻ Decays

In the pursuit of physics beyond the Standard Model, a promising path is the study of B-meson decays caused by the transition b → sℓ ⁺ℓ ⁻. A key observable in such decays is the ratio R _K, which measures electron-muon universality in (Formula Presented). At first sight, the recent LHCb measurement of R _K ∼ 1 may seem to largely constrain deviations from universality in these decays. However, we show that this is actually not the case: new sources of CP violation allow for significant universality violation consistent with R _K ∼ 1. This provides an exciting new opportunity to search for New Physics by measuring differences between CP asymmetries in (Formula Presented).