Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays
Abstract
A distinct peak is observed in the pi^+/- psi' invariant mass distribution near 4.43 GeV in B->K pi^+/- psi' decays. A fit using a Breit Wigner resonance shape yields a peak mass and width of 4433+-4(stat)+-1(syst) MeV and Gamma = 44^+17_-13(stat) ^+30_-11 MeV. The product branching fraction is determined to be Bf(B-->KZ(4430))xBf(Z(4430)-->pi^+psi') = (4.1+-1.0(stat)+-1.3(syst))x10^{-5), where Z(4430) is used to designate the observed structure. The statistical significance of the observed peak is greater than 7sigma. These results are obtained from a 605 fb-1 data sample that contains 657 million BBbar pairs collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider.Keywords
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