MEASUREMENTS OF LIFETIMES AND A LIMIT ON THE LIFETIME DIFFERENCE IN THE NEUTRAL D-MESON SYSTEM

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we report the first directly measured constraint on the decay-width difference {Delta}{Gamma} for the mass eigenstates of the D{sup 0} -{ovr D}{sup 0} system. We obtain our result from lifetime measurements of the decays D{sup 0}{r_arrow}K{sup {minus}}{pi}{sup +} and D{sup 0}{r_arrow}K{sup {minus}}K{sup +} , under the assumption of {ital CP} invariance, which implies that the {ital CP} eigenstates and the mass eigenstates are the same. The lifetime of D{sup 0}{r_arrow}K{sup {minus}}K{sup +} (the {ital CP}-even final state) is {tau}{sub KK}=0.410{plus_minus}0.011{plus_minus}0.006 ps , and the lifetime of D{sup 0}{r_arrow}K{sup {minus}}{pi}{sup +} (an equal mixture of {ital CP}-odd and {ital CP}-even final states) is {tau}{sub K{pi}}=0.413{plus_minus}0.003{plus_minus}0.004 ps . The decay-width difference is {Delta}{Gamma}=2({Gamma}{sub KK}{minus}{Gamma}{sub K {pi}})=0.04{plus_minus}0.14{plus_minus}0.05 ps{sup {minus}1} . We relate these measurements to measurements of mixing in the neutral D -meson system. {copyright} {ital 1999} {ital The American Physical Society}