Study of the B- → J/ψK-π+π- decay and measurement of the B- → X(3872)K- branching fraction -: art. no. 071103

We study the decay B--> J/psi K(-)pi(+)pi(-) using 117x10(6) B (B) over bar events collected at the Y(4S) resonance with the BABAR detector at the PEP-II e(+)e(-) asymmetric-energy storage ring. We measure the branching fractions B (B--> J/psi K(-)pi(+)pi(-))=(116 +/- 7(stat.)+/- 9(syst.))x10(-5) and B (B--> X(3872)K-)x B (X(3872)-> J/psi pi(+)pi(-))=(1.28 +/- 0.41)x10(-5) and find the mass of the X(3872) to be 3873.4 +/- 1.4 MeV/c(2). We search for the h(c) narrow state in the decay B--> h(c)K(-), h(c)-> J/psi pi(+)pi(-) and for the decay B--> J/psi D(0)pi(-), with D-0-> K(-)pi(+). We set the 90% C.L. limits B(B--> h(c)K(-))xB(h(c)-> J/psi pi(+)pi(-))< 3.4x10(-6) and B(B--> J/psi D(0)pi(-)) < 5.2x10(-5).