Study of the K(+)pi(+)pi(-) final state in B(+) -> J/psiK(+)pi(+)pi(-) and B(+) -> psi(prime)K(+)pi(+)pi(-)

Abstract

Using 535×106 B-meson pairs collected by the Belle detector at the KEKB e+e- collider, we measure branching fractions of (7.16±0.10(stat)±0.60(syst)×10-4 for B +→J/ψK+π+π- and (4.31±0.20(stat)±0.50(syst))×10-4 for B +→ψ′K+π+π -. We perform amplitude analyses to determine the resonant structure of the K+π+π- final state in B +→J/ψK+π+π- and B+→ψ′K+π+π - and find that the K1(1270) is a prominent component of both decay modes. There is significant interference among the different intermediate states, which leads, in particular, to a striking distortion of the ρ line shape due to the ω. Based on the results of the fit to the B+→J/ψK+π+π- data, the relative decay fractions of the K1(1270) to Kρ, Kω, and K*(892)π are consistent with previous measurements, but the decay fraction to K0*(1430) is significantly smaller. Finally, by floating the mass and width of the K1(1270) in an additional fit of the B+→J/ψK+π+π- data, we measure a mass of (1248.1±3.3(stat)±1.4(syst))MeV/c2 and a width of (119.5±5.2(stat)±6.7(syst))MeV/c2 for the K 1(1270).