RevisitingD0−D¯0mixing using U-spin

Abstract

We prove that ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing in the standard model occurs only at second order in U-spin breaking. The U-spin subgroup of SU(3) is found to be a powerful tool for analyzing the cancellation of intermediate-state contributions to the ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing parameter $y=\ensuremath{\Delta}\ensuremath{\Gamma}/(2\ensuremath{\Gamma})$. Cancellations due to states within a single U-spin triplet are shown to be valid to first order in U-spin breaking. Illustrations are given for triplets consisting of (a) pairs of charged pions and kaons; (b) pairs of neutral pseudoscalar members of the meson octet; (c) charged vector-pseudoscalar pairs, and (d) states of four charged kaons and pions.