Evidence for D0-D0bar mixing using the CDF II Detector

TL;DR

This paper presents evidence for D0-D0bar mixing by analyzing decay rate ratios over time using data from the CDF II detector, providing key measurements that challenge the no-mixing hypothesis.

Contribution

First measurement of D0-D0bar mixing parameters using time-dependent decay ratios with a large data sample from the CDF II detector.

Findings

Measured mixing parameters Rd, y', and x'^2 with uncertainties.

Data inconsistent with no-mixing hypothesis at 3.8 sigma.

Bayesian probability contours support evidence for mixing.

Abstract

We measure the time dependence of the ratio of decay rates for the rare decay D0->K+pi- to the Cabibbo-favored decay D0->K-pi+. We use a signal of 12.7 x10^3 D0->K+pi decays with proper decay times between 0.75 and 10 mean D0 lifetimes. The data sample was recorded with the CDF II detector at the Fermilab Tevatron and corresponds to an integrated luminosity of 1.5 fb-1 of p-pbar collisions at sqrt(s) = 1.96 TeV. We search for D0-D0bar mixing and measure the mixing parameters to be Rd = (3.04 +/- 0.55) x10^{-3}, y' = (8.5 +/- 7.6) x10^{-3}, and x'^2 = (-0.12 +/- 0.35) x10^{-3}. We report Bayesian probability contours in the x'^2-y' plane and find that the data are inconsistent with the no-mixing hypothesis with a probability equivalent to 3.8 Gaussian standard deviations.