Measurement of the charm mixing parameter y(CP)-y(CP)(K pi) using two-body D-0 meson decays

A measurement of the ratios of the effective decay widths of D-0 -> pi(-)pi(+) and D-0 -> K- K+ decays over that of D-0 -> K-pi(+) decays is performed with the LHCb experiment using proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb(-1). These observables give access to the charm mixing parameters y(CP)(pi pi) - y(CP)(K pi )and y(CP)(KK) -y(CP)(K pi), and are measured as y(CP)(pi pi) - y(CP)(K pi) = (6.57 +/- 0.53 +/- 0.16) x 10(-3), y(CP)(KK) - y(CP)(K pi) = (7.08 +/- 0.30 +/- 0.14) x 10(-3), where the first uncertainties are statistical and the second systematic. The combination of the two measurements is Y-CP - y(CP)(K pi) = (6.96 +/- 0.26 +/- 0.13) x 10(-3), which is four times more precise than the previous world average.