A precision measurement of the branching ratio K$^{+}$ --> $\pi^{+}\pi^{0}$/K$^{+}$ --> $\mu^{+}\nu_{\mu}$

A measurement of the branching ratio K+→π+π0K+→μ+νμ was made using stopped kaons from pp¯ annihilations at rest and a magnetic spectrometer to measure the momenta of the charged decay product to the 1% to 1.5% level. The determination is based on 45 500 events passing final data cuts. The resulting ratio is 0.3329±0.0047 (statistical) ±0.0010 (systematic).