Measurement of y_(CP) in D⁰ meson decays to the K_S⁰K^+K^- final state

We present a measurement of the $D^0$-$\overline{D}{}^0$ mixing parameter $y_{CP}$ using a flavor-untagged sample of $D^0\to K_S^0K^+K^-$ decays. The measurement is based on a 673 fb$^{-1}$ data sample recorded with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. Using a method based on measuring the mean decay time for different $K^+K^-$ invariant mass intervals, we find $y_{CP} = (+0.11\pm 0.61 ({\rm stat.})\pm 0.52 (\rm syst.))%$.