First observation of the decays B0bar -->D+ K- pi+ pi- and B- --> D0 K- pi+ pi-

TL;DR

This paper reports the first observation and measurement of the branching fractions of two Cabibbo suppressed B meson decays involving D mesons and multiple pions, using data from the LHCb detector.

Contribution

First observation and branching fraction measurements of B0bar --> D+ K- pi+ pi- and B- --> D0 K- pi+ pi- decays, providing new data for CKM phase gamma studies.

Findings

Measured branching fraction ratios with statistical and systematic uncertainties.

First observation of these specific decay modes.

Potential use of B- --> D0 K- pi+ pi- in CKM gamma measurements.

Abstract

First observations of the Cabibbo suppressed decays B0bar -->D+ K- pi+ pi- and B- --> D0 K- pi+ pi- are reported using 35 pb^{-1} of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo favored decays, from which we obtain B(B0bar --> D+ K- pi+ pi-)/B(B0bar --> D+ pi- pi+ pi-)=(5.9\pm1.1\pm0.5) x 10^{-2} and B(B- --> D0 K- pi+ pi-)/B(B- --> D0 pi- pi+ pi-)=(9.4\pm1.3\pm0.9) x 10^{-2}, where the uncertainties are statistical and systematic, respectively. The B- --> D0 K- pi+ pi- decay is particularly interesting, as it can be used in a similar way to B- --> D0 K- to measure the CKM phase gamma.