K - 073 Analysis of the 1 / 3 E 949 pnn 2 data

The pnn2 analysis of the 1/3 data sample for the E949 exposure of 1.7 × 1012 stopped kaons is described. The signal region has been expanded with respect to the previous pnn2 analyses and divided into nine cells with differing signal-tobackground to permit a likelihood-based analysis. The single-event sensitivity and background of the entire signal region is (0.432 ± 0.015 −0.046) × 10−9 and 0.966 ± 0.220 −0.246, respectively, and is (1.325±0.389 −0.143)×10 and 0.174±0.068 −0.035 , respectively, in the cleanest cell. Potential observations of 0, 1 or 2 candidates distributed within the signal region have been evaluated and it is expected that the results of this analysis will produce a modest improvement (∼10%) in the precision of the combined E787+E949 measurement of the K+ → π+νν̄ branching fraction.