New, high statistics measurement of the K+ ---> pi0 e+ nu (K+(e3)) branching ratio

E865 at the Brookhaven National Laboratory AGS collected about 70 000 K + e3 events to measure the K + e3 branching ratio relative to the observed K + → π + π 0 , K + → π 0 μ + ν, and K + → π + π 0 π 0 decays. The π 0 in all the decays was detected using the e + e - pair from π 0 → e + e - γ decay and no photons were required. Using the 2002 Particle Data Group branching ratios for the normalization decays, we obtain BR(K + e3(γ)) = (5.13 ′ 0.02 s t a t ′ 0.09 s y s t ′ 0.04 n o r m )%, where K + e3(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 V u s element of the CKM matrix, and the matrix's unitarity are discussed.