Study of B0→D* -^π+π^-π+ and B0→D*-^K+π-^π+ decays

Using proton-proton collision data collected by the LHCb experiment at √s=7 TeV, corresponding to an integrated luminosity of 1.0 fb ^-1, the ratio of branching fractions of the B0→D* ^-π ⁺π ^-π ⁺ decay relative to the B0→D* ^-π ⁺ decay is measured to be B(B0→D* ^-π ⁺π ^-π ⁺) B(B0→D* ^-π ⁺)=2.64±0.04(stat)±0. 13(syst). The Cabibbo-suppressed decay B0→D* ^-K ⁺π ^-π ⁺ is observed for the first time, and the measured ratio of branching fractions is B(B0→D* ^-K ⁺π ^-π ⁺)B(B0→D* ^-π ⁺π ^-π ⁺)=(6.47±0. 37(stat)±0.35(syst))×10 ^-2. A search for orbital excitations of charm mesons contributing to the B0→D* ^-π ⁺π ^-π ⁺ final state is also performed, and the first observation of the B0→D _̄1 ⁽²⁴²⁰⁾0π ⁺π ^- decay is reported with the ratio of branching fractions B(B0→(D _̄1 ⁽²⁴²⁰⁾0→D* ^-π ⁺) π ^-π ⁺)B(B0→D* ^-π ⁺π ^-π ⁺)=(2.04±0.42(stat)±0. 22(syst))×10 ^-2, where the numerator represents a product of the branching fractions B(B0→D _̄1 ⁽²⁴²⁰⁾0π ^-π ⁺) and B(D _̄1 ⁽²⁴²⁰⁾0→D* ^-π ⁺).