Observation of a resonancelike structure in the π -ψ′ mass distribution in exclusive B→Kπ -ψ′ decays

Abstract

A distinct peak is observed in the π±ψ′ invariant mass distribution near 4.43 GeV in B→Kπ±ψ′ decays. A fit using a Breit-Wigner resonance shape yields a peak mass and width of M=4433±4(stat)±2(syst)MeV and Γ=45-13+18(stat)-13+30(syst) MeV. The product branching fraction is determined to be B(B0→K Z±(4430))×B(Z±(4430)→π±ψ′)=(4. 1±1.0(stat)±1.4(syst))×10-5, where Z±(4430) is used to denote the observed structure. The statistical significance of the observed peak is 6.5σ. These results are obtained from a 605fb-1 data sample that contains 657×106 BB̄ pairs collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. © 2008 The American Physical Society..