Observation of a rare beta decay of the charmed baryon with a Graph Neural Network

Abstract

The beta decay of the lightest charmed baryon $\hat{I}{›}_c^{+}$ provides unique insights into the fundamental mechanism of strong and electro-weak interactions, serving as a testbed for investigating non-perturbative quantum chromodynamics and constraining the Cabibbo-Kobayashi-Maskawa (CKM) matrix parameters. This article presents the first observation of the Cabibbo-suppressed decay $\hat{I}{›}_c^{+}\to n{e}^{+}\hat{I}{½}_e$, utilizing $4.5{\mathrm{fb}}^{-1}$ of electron-positron annihilation data collected with the BESIII detector. A novel Graph Neural Network based technique effectively separates signals from dominant backgrounds, notably $\hat{I}{›}_c^{+}\to \hat{I}›e^{+}\hat{I}{½}_e$, achieving a statistical significance exceeding $10\ddot{I}ƒ$. The absolute branching fraction is measured to be $(3.57\pm 0.34_{stat.}\pm 0.14_{syst.})\times 10^{-3}$. For the first time, the CKM matrix element $\left|V_{cd}\right|$ is extracted via a charmed baryon decay as $0.208\pm 0.011_{exp.}\pm 0.007_{\mathrm{LQCD}}\pm 0.001_{\ddot{I}{„}_{\hat{I}{›}_c^{+}}}$. This work highlights a new approach to further understand fundamental interactions in the charmed baryon sector, and showcases the power of modern machine learning techniques in experimental high-energy physics.

27 pages, 5 figures