ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2008, vol. 78, p. -
Observation of two resonancelike structures: Observation of two resonancelike structures in the Ic1 mass distribution in exclusive BA0K-I+Ic1
© 2008 The American Physical Society. We report the first observation of two resonancelike structures in the π+χc1 invariant mass distribution near 4.1GeV/c2 in exclusive B¯0→K-π+χc1 decays. From a Dalitz plot analysis in which the π+χc1 mass structures are represented by Breit-Wigner resonance amplitudes, we determine masses and widths of: M1=(4051±14-41+20)MeV/c2, Γ1=(82-17-22+21+47)MeV, M2=(4248-29-35+44+180)MeV/c2, and Γ2=(177-39-61+54+316)MeV; and product branching fractions of B(B¯0→K-Z1,2+)×B(Z1,2+→π+χc1)=(3.0-0.8-1.6+1.5+3.7)×10-5 and (4.0-0.9-0.5+2.3+19.7)×10-5, respectively. Here the first uncertainty is statistical, the second is systematic. The significance of each of the π+χc1 structures exceeds 5σ, including the systematic uncertainty from various fit models. This analysis is based on 657×106 BB¯ events collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.