Measurement of the Branching Fraction for D^+ \to K^- π^+ π^+

Using the CLEO-II detector at CESR we have measured the ratio of branching fractions, ${\cal B}(D^+\rightarrow K^- \pi^+ \pi^+)/{\cal B}(D^0 \rightarrow K^-\pi^+) = 2.35 \pm 0.16 \pm 0.16$. Our recent measurement of ${\cal B}(D^0 \rightarrow K^-\pi^+)$ then gives ${\cal B}(D^+\rightarrow K^- \pi^+ \pi^+) = (9.3 \pm 0.6 \pm 0.8)\%$.