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→Dˉ1(2420)0π+π− decay is reported with the ratio of branching fractions
B(B0→(Dˉ1(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→Dˉ1(2420)0π−π+) and B(Dˉ1(2420)0→D∗−π+).