Study of the B-→J/ψK-π+π- decay and measurement of the B-→X(3872)K- branching fraction

We study the decay B-→J/ψK-π+π- using 117×106 BB̅ 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/ψK-π+π-)=(116±7(stat.)±9(syst.))×10-5 and B (B-→X(3872)K-)× B (X(3872)→J/ψπ+π-)=(1.28±0.41)×10-5 and find the mass of the X(3872) to be 3873.4±1.4  MeV/c2. We search for the hc narrow state in the decay B-→hcK-, hc→J/ψπ+π- and for the decay B-→J/ψD0π-, with D0→K-π+. We set the 90% C.L. limits B(B-→hcK-)×B(hc→J/ψπ+π-)<3.4×10-6 and B(B-→J/ψD0π-)<5.2×10-5.