Observation of a rare beta decay of the charmed baryon with a Graph Neural Network.
basic_science · Level V
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- Record sourced from PubMed, PMID 39814737.
- Also identified by DOI 10.1038/s41467-024-55042-y and PMC identifier 11735802.
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Abstract
The beta decay of the lightest charmed baryon <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>Λ</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> 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 <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>Λ</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mo>+</mo></mrow> </msubsup> <mo>→</mo> <mi>n</mi> <msup><mrow><mi>e</mi></mrow> <mrow><mo>+</mo></mrow> </msup> <msub><mrow><mi>ν</mi></mrow> <mrow><mi>e</mi></mrow> </msub> </math> , utilizing 4.5 fb<sup>-1</sup> of electron-positron annihilation data collected with the BESIII detector. A novel Graph Neural Network based technique effectively separates signals from dominant backgrounds, notably <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>Λ</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mo>+</mo></mrow> </msubsup> <mo>→</mo> <mi>Λ</mi> <msup><mrow><mi>e</mi></mrow> <mrow><mo>+</mo></mrow> </msup> <msub><mrow><mi>ν</mi></mrow> <mrow><mi>e</mi></mrow> </msub> </math> , achieving a statistical significance exceeding 10σ. The absolute branching fraction is measured to be (3.57 ± 0.34<sub>stat.</sub> ± 0.14<sub>syst.</sub>) × 10<sup>-3</sup>. For the first time, the CKM matrix element <math xmlns="http://www.w3.org/1998/Math/MathML"> <mfenced> <mrow> <msub><mrow><mi>V</mi></mrow> <mrow><mi>c</mi> <mi>d</mi></mrow> </msub> </mrow> </mfenced> </math> is extracted via a charmed baryon decay as <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>0.208</mn> <mo>±</mo> <mn>0.01</mn> <msub><mrow><mn>1</mn></mrow> <mrow><mi>exp.</mi></mrow> </msub> <mo>±</mo> <mn>0.00</mn> <msub><mrow><mn>7</mn></mrow> <mrow><mi>LQCD</mi></mrow> </msub> <mo>±</mo> <mn>0.00</mn> <msub><mrow><mn>1</mn></mrow> <mrow> <msub><mrow><mi>τ</mi></mrow> <mrow> <msubsup><mrow><mi>Λ</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mo>+</mo></mrow> </msubsup> </mrow> </msub> </mrow> </msub> </math> . 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.