Measurement of the ratio of branching fractions B(D(0)-> K(+)pi(-))/B(D(0)-> K(-)pi(+)) using the CDF II detector

We present a measurement of RB, the ratio of the branching fraction for the rare decay D(0)-> K(+)pi(-) to that for the Cabibbo-favored decay D(0)-> K(-)pi(+). Charge-conjugate decays are implicitly included. A signal of 2005 +/- 104 events for the decay D(0)-> K(+)pi(-) is obtained using the CDF II detector at the Fermilab Tevatron collider. The data set corresponds to an integrated luminosity of 0.35 fb(-1) produced in (p) over barp collisions at root s>=1.96 TeV. Assuming no mixing, we find R(E)=[4.05 +/- 0.21(stat)+/- 0.11(syst)]x10(-3). This measurement is consistent with the world average, and comparable in accuracy with the best measurements from other experiments.