Observation of New States Decaying into $\Lambda_c^+ K^-\pi^+$ and $\Lambda_c^+ K^0_S\pi^-$

TL;DR

This paper reports the first observation of two new charmed strange baryons decaying into specific final states, measuring their masses and widths, and searching for isospin partners using Belle detector data.

Contribution

The study provides the first observation and precise measurements of two new charmed strange baryons and explores their isospin partner states.

Findings

Two new baryons observed with specific masses and widths.

Measured masses: 2978.5 MeV/c^2 and 3076.7 MeV/c^2.

Significant signal for isospin partner at 3082.8 MeV/c^2.

Abstract

We report the first observation of two charmed strange baryons that decay into $\Lambda_c^+ K^-\pi^+$. The broader of the two states is measured to have a mass of $2978.5\pm 2.1\pm 2.0$ MeV/$c^2$ and a width of $43.5\pm 7.5\pm 7.0$ MeV/$c^2$. The mass and width of the narrow state are measured to be $3076.7\pm 0.9\pm 0.5$ MeV/$c^2$ and $6.2\pm 1.2\pm 0.8$ MeV/$c^2$, respectively. We also perform a search for the isospin partner states that decay into $\Lambda_c^+ K_S^0\pi^-$ and observe a significant signal at the mass of $3082.8\pm 1.8\pm 1.5$ MeV/$c^2$. The data used for this analysis was accumulated at or near the $\Upsilon(4S)$ resonance, using the Belle detector at the $e^+ e^-$ asymmetric-energy collider KEKB. The integrated luminosity of the data sample used is $461.5 ~\mathrm{fb}^{-1}$.