Plot showing the only two known examples of the rare decay K ^{+ +}  ; the new data point (white dot inside the box) confirms an earlier identification (red triangle). The blue dots are from a simulation of expected events, while data points outside the box are due to background 2-pion decays. The data for this decay, the focus of many decades of effort, yield a branching ratio that agrees within error bars with the standard-model prediction.

From the article:

Further Evidence for the Decay ${\mathit{K}}^{+}\to {\pi }^{+}\nu \overline{\nu }$
S. Adler et al. (E787 Collaboration)
Phys. Rev. Lett. 88, 041803 (2002)

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