Determination of parallel to V-ub parallel to from measurements of the inclusive charmless semileptonic partial rates of B mesons using full reconstruction tags

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element parallel to V(ub)parallel to, based on 253 fb(-1) of data collected by the Belle detector at the KEKB e(+)e(-) asymmetric collider. Events are tagged by fully reconstructing one of the B mesons, produced in pairs from Upsilon(4S). The signal for b -> u semileptonic decay is distinguished from the b -> c background using the hadronic mass M-X, the leptonic invariant mass squared q(2) and the variable P(+)equivalent to E-X-parallel to p ->(X)parallel to. The results are obtained for events with p(center dot)(*)>= 1 GeV/c, in three kinematic regions (1) M-X 8 GeV2/c(2), and by (3) P+< 0.66 GeV/c. The matrix element parallel to V(ub)parallel to is found to be (4.09 +/- 0.19 +/- 0.20(-0.15)(+0.14)+/- 0.18)x10(-3), where the errors are statistical, systematic including Monte Carlo modeling, theoretical, and from shape function parameter determination, respectively.