Study of the decay mechanism for B+→pp¯K+ and B+→pp¯π+

We study the characteristics of the low mass pp¯ enhancements near threshold in the three-body decays B+→pp¯K+ and B+→pp¯π+. We observe that the proton polar angle distributions in the pp¯ helicity frame in the two decays have the opposite polarity, and measure the forward-backward asymmetries as a function of the pp¯ mass for the pp¯K+ mode. We also search for the intermediate two-body decays, B+→p¯Δ++ and B+→pΔ¯0, and set upper limits on their branching fractions. These results are obtained from a 414fb−1 data sample that contains 449×106BB¯ events collected near the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider.