Measurement of CP violation in B0 → D+D− and \( {\textrm{B}}_{\textrm{s}}^0 \) → \( {\textrm{D}}_{\textrm{s}}^{+}{\textrm{D}}_{\textrm{s}}^{-} \) decays

Abstract

A time-dependent, flavour-tagged measurement of CP violation is performed with B⁰ → D⁺D⁻ and \( {B}_s^0 \) → \( {D}_s^{+}{D}_s^{-} \) decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 6 fb⁻¹. In B⁰ → D⁺D⁻ decays the CP-violation parameters are measured to be

In \( {B}_s^0 \) → \( {D}_s^{+}{D}_s^{-} \) decays the CP-violating parameter formulation in terms of ϕ_s and |λ| results in

These results represent the most precise single measurement of the CP-violation parameters in their respective channels. For the first time in a single measurement, CP symmetry is observed to be violated in B⁰ → D⁺D⁻ decays with a significance exceeding six standard deviations.