Observation of two resonancelike structures in the pi(+)chi(c1) mass distribution in exclusive (B)overbar(0)-> K-pi(+)chi(c1) decays

Abstract

We report the first observation of two resonancelike structures in the pi(+)chi(c1) invariant mass distribution near 4.1 GeV/c(2) in exclusive (B)overbar(0)-> K-pi(+)chi(c1) decays. From a Dalitz plot analysis in which the pi(+)chi(c1) mass structures are represented by Breit-Wigner resonance amplitudes, we determine masses and widths of: M-1=(4051 +/- 14(-41)(+20)) MeV/c(2), Gamma(1)=(82(-17-22)(+21+47)) MeV, M-2=(4248(-29-35)(+44+180)) MeV/c(2), and Gamma(2)=(177(-39-61)(+54+316)) MeV; and product branching fractions of B((B)overbar(0)-> K(-)Z(1,2)(+))xB(Z(1,2)(+)->pi(+)chi(c1))=(3.0(-0.8-1.6)(+1.5+3.7))x10(-5) and (4.0(-0.9-0.5)(+2.3+19.7))x10(-5), respectively. Here the first uncertainty is statistical, the second is systematic. The significance of each of the pi(+)chi(c1) structures exceeds 5 sigma, including the systematic uncertainty from various fit models. This analysis is based on 657x10(6) B(B)overbar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.