New, high statistics measurement of the K+ → π0e+v (Ke3+) branching ratio

E865 at the Brookhaven National Laboratory AGS collected about 70,000 Ke3+ events to measure the Ke3+ branching ratio relative to the observed K+ → π+π0, K+ → π0μ+v, and K+ → π+π0π0 decays. The π0 in all the decays was detected using the e+e- pair from π0 → e+e-γ decay and no photons were required. Using the Particle Data Group branching ratios for the normalization decays we obtain BR(Ke3(γ)+) = (5.13 ± 0.02stat ± 0.09sys ± 0.04norm)%, where Ke3(γ)+ includes the effect of virtual and real photons. This result is ≅ 2.3σ higher than the current Particle Data Group value. Implications for the Vus element of the CKM matrix, and the matrix's unitarity are discussed