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 $R_{\mathrm{D}}$, 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.

6 pages, 4 figures; Submitted to the proceedings of the XLIInd Rencontres de Moriond Electroweak Interactions and Unified Theories, March 10-17 2007, and the XLIInd Rencontres de Moriond QCD and Hadronic Interactions, March 17-24 2007, La Thuile, Italy