Observation of Cabibbo-suppressed and W-exchange Lambda_c^+ baryon decays

TL;DR

This paper reports the first observations and improved measurements of several Cabibbo-suppressed and W-exchange decay modes of the Lambda_c^+ baryon, using data from the Belle detector at KEKB.

Contribution

It presents the first observations of certain Lambda_c^+ decay modes and provides improved branching ratio measurements, highlighting the role of W-exchange diagrams.

Findings

First observation of Lambda_c^+ --> Lambda0 K+ and Lambda_c^+ --> Sigma0 K+ decays.

Large-statistics observation of Lambda_c^+ --> Sigma+ K+ pi- decay.

Improved measurements of branching ratios for Lambda_c^+ --> Sigma+ K+ K- and Lambda_c^+ --> Sigma+ phi.

Abstract

We present measurements of the Cabibbo-suppressed decays Lambda_c^+ --> Lambda0 K+ and Lambda_c^+ --> Sigma0 K+ (both first observations), Lambda_c^+ --> Sigma+ K+ pi- (seen with large statistics for the first time), Lambda_c^+ --> p K+ K- and Lambda_c^+ --> p phi (measured with improved accuracy). Improved branching ratio measurements for the decays Lambda_c^+ --> Sigma+ K+ K- and Lambda_c^+ --> Sigma+ phi, which are attributed to W-exchange diagrams, are shown. We also present the first evidence for Lambda_c^+ --> Xi(1690)^0 K+ and set an upper limit on the non-resonant decay Lambda_c^+ --> Sigma+ K+ K-. This analysis was performed using 32.6 fb^{-1} of data collected by the Belle detector at the asymmetric e+ e- collider KEKB.