Observation of D0−¯¯¯D0 Oscillations

Abstract

We report a measurement of the time-dependent ratio of D 0 → K + π − to D 0 → K − π + decay rates in D * + -tagged events using 1.0 fb − 1 of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters x ' 2 = ( − 0.9 ± 1.3 ) × 10 − 4 , y ′ = ( 7.2 ± 2.4 ) × 10 − 3 , and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R D = ( 3.52 ± 0.15 ) × 10 − 3 , where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D 0 − ¯¯¯ D 0 oscillations from a single measurement.