First Observation of the Cabibbo-suppressed Decays Xi_c+ -> Sigma+ pi- pi+ and Xi_c+ -> Sigma- pi+ pi+ and Measurement of their Branching Ratios

TL;DR

This paper reports the first observation of two specific Cabibbo-suppressed decay modes of Xi_c+ baryons and measures their branching ratios relative to known decay channels, providing new experimental data in charm baryon decays.

Contribution

It presents the first experimental observation and measurement of branching ratios for two Cabibbo-suppressed Xi_c+ decay modes, expanding knowledge of charm baryon decay processes.

Findings

Observed 59±14 events for Xi_c+ -> Sigma+ pi- pi+

Observed 22±8 events for Xi_c+ -> Sigma- pi+ pi+

Measured branching ratios relative to Xi- pi+ pi+ decay mode

Abstract

We report the first observation of two Cabibbo-suppressed decay modes, Xi_c+ -> Sigma+ pi- pi+ and Xi_c+ -> Sigma- pi+ pi+. We observe 59+/-14 over a background of 87, and 22+/-8 over a background of 13 events, respectively, for the signals. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600GeV/c Sigma- beam. The branching ratios of the decays relative to the Cabibbo--favored Xi_c+ -> Xi- pi+ pi+ are measured to be B(Xi_c+ -> Sigma+ pi- pi+)/B(Xi_c+ -> Xi- pi+ pi+) = 0.48+/-0.20, and B(Xi_c+ -> Sigma- pi+ pi+)/B(Xi_c+ -> Xi- pi+ pi+) = 0.18+/-0.09, respectively. We also report branching ratios for the same decay modes of the Lambda_c+ relative to Lambda_c+ -> p K- pi+.