Experimental limits on weak annihilation contributions to b -> ul nu decays

Abstract

We present the first experimental limits on high-q(2) contributions to charmless semileptonic B decays of the form expected from the weak annihilation (WA) decay mechanism. Such contributions could bias determinations of vertical bar V(ub)vertical bar from inclusive measurements of B -> X(u)l nu. Using a wide range of models based on available theoretical input we set a limit of Gamma(WA)/Gamma(b -> u)< 7.4% (90% confidence level) on the WA fraction, and assess the impact on previous inclusive determinations of vertical bar V(ub)vertical bar.