Study of B0 -> D*- pi+ pi- pi+ and B0 -> D*- K+ pi- pi+ decays

TL;DR

This paper reports measurements of branching fractions for B0 decays involving D* and multiple pions or kaons, including the first observation of a specific decay mode and searches for charm meson excitations, using LHCb data at 7 TeV.

Contribution

It provides new measurements of branching ratios for B0 decays and reports the first observation of B0 -> Dbar_{1}(2420)^0 pi+ pi- decay, expanding understanding of B meson decay channels.

Findings

Measured ratio B(B0 -> D*- pi+ pi- pi+) / B(B0 -> D*- pi+) = 2.64 1 0.04 (stat.) 1 0.13 (syst.)

First observation of B0 -> Dbar_{1}(2420)^0 pi+ pi- decay with a ratio of (2.04 1 0.42 (stat.) 1 0.22 (syst.)) 7 10^{-2}

Observed the Cabibbo-suppressed decay B0 -> D*- K+ pi- pi+ for the first time.

Abstract

Using proton-proton collision data collected by the LHCb experiment at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 1.0 fb^{-1}, the ratio of branching fractions of the B0 -> D*- pi+ pi- pi+ decay relative to the B0 -> D*- pi+ decay is measured to be B(B0 -> D*- pi+ pi- pi+) / B(B0 -> D*- pi+) = 2.64 \pm 0.04 (stat.) \pm 0.13 (syst.). The Cabibbo-suppressed decay B0 -> D*- K+ pi- pi+ is observed for the first time and the measured ratio of branching fractions is B(B0 -> D*- K+ pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (6.47 \pm 0.37 (stat.) \pm 0.35 (syst.)) x 10^{-2}. A search for orbital excitations of charm mesons contributing to the B0 -> D*- pi+ pi- pi+ final state is also performed, and the first observation of the B0 -> Dbar_{1}(2420)^0 pi+ pi- decay is reported with the ratio of branching fractions B(B0 -> (Dbar_{1}(2420)^0 -> D*- pi+) pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (2.04 \pm 0.42 (stat.) \pm 0.22 (syst.)) x 10^{-2}, where the numerator represents a product of the branching fractions B(B0 -> Dbar_{1}(2420)^0 pi- pi+) and B(Dbar_{1}(2420)^0 -> D*- pi+).