Improved measurement of absolute branching fraction of the inclusive decay $\Lambda_{c}^{+} \to K_{S}^{0} X$

TL;DR

This paper measures the absolute branching fraction of the inclusive decay ^{+}  K_{S}^{0} X using BESIII data, revealing potential undiscovered decay channels and confirming predictions of the statistical isospin model.

Contribution

First precise measurement of the inclusive ^{+}  K_{S}^{0} X decay branching fraction using the double-tag technique.

Findings

Measured ^{+} o K_{S}^{0} X BF as (10.9 1 1)%.

Identified a ^{+} o K_{S}^{0} X decay channel with a BF of (3.1 4)% that remains to be explored.

Confirmed the statistical isospin model prediction for the ^{+} o ar{K}^{0}/K^{0} X decay BF.

Abstract

By analyzing $4.5$ fb$^{-1}$ of $e^{+}e^{-}$ collision data accumulated with the BESIII detector at center-of-mass energies ranging from $4599.53$ MeV to $4698.82$ MeV, we report the measurement of the absolute branching fraction (BF) of the inclusive decay $\Lambda_{c}^{+} \to K_{S}^{0} X$ using the double-tag technique. The result is $\mathcal{B}(\Lambda_{c}^{+} \to K_{S}^{0} X)=(10.9\pm0.2\pm0.1)\%$, where the first uncertainty is statistical and the second is systematic. This result indicates that there are still undiscovered decay channels containing $K_{S}^{0}$ in the final state with a combined BF of $(3.1\pm0.4)\%$. The BF of the inclusive decay $\Lambda_{c}^{+} \to \overline{K}^{0} / K^{0} X$ is calculated to be $\mathcal{B}(\Lambda_{c}^{+} \to \overline{K}^{0} / K^{0} X)=(21.8 \pm0.4 \pm0.2 \pm1.1)\%$, where the third uncertainty accounts for a possible difference between $\mathcal{B}(\Lambda_{c}^{+} \to K_{S}^{0} X)$ and $\mathcal{B}(\Lambda_{c}^{+} \to K_{L}^{0} X)$. The result is in agreement with the prediction of the statistical isospin model.