Evidence for D0-D0bar Mixing at Babar

Abstract

We present evidence for D0-D0bar mixing in $D^0 \to K^{+}\pi^{-}$ decays from 384 fb^{-1} of e+e- colliding-beam data recorded near sqrt(s)=10.6 GeV with the Babar detector at the PEP-II storage rings at SLAC. We find the mixing parameters ${x^{\prime}}^2 = [-0.22 \pm 0.30 (stat.) \pm 0.21 (syst.)] \times 10^{-3}$ and $y^{\prime} = [9.7 \pm 4.4 (stat.) \pm 3.1 (syst.)] \times 10^{-3}$, and a correlation between them of -0.94. This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure $R_{\rm D}$, the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be $[0.303 \pm 0.016 (stat.) \pm 0.010 (syst.)] %$. We find no evidence for CP violation.