The beta decay of the lightest charmed baryon $${\Lambda }_{c}^{+}$$ 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 $${\Lambda }_{c}^{+}\to n{e}^{+}{\nu }_{e}$$ , utilizing 4.5 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 $${\Lambda }_{c}^{+}\to \Lambda {e}^{+}{\nu }_{e}$$ , achieving a statistical significance exceeding 10σ. The absolute branching fraction is measured to be (3.57 ± 0.34stat. ± 0.14syst.) × 10−3. For the first time, the CKM matrix element $$\left\vert {V}_{cd}\right\vert$$ is extracted via a charmed baryon decay as $$0.208\pm 0.01{1}_{{{{\rm{exp.}}}}}\pm 0.00{7}_{{{{\rm{LQCD}}}}}\pm 0.00{1}_{{\tau }_{{\Lambda }_{c}^{+}}}$$ . 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. The semileptonic decay channels of the Λc baryon can give important insights into weak interaction, but decay into a neutron, positron and electron neutrino has not been reported so far, due to difficulties in the final products' identification. Here, the BESIII Collaboration reports its observation in e+e- collision data, exploiting machine-learning-based identification techniques.
The reversible conversion reaction of a SEI was enabled by FeN X catalysts, which provided novel avenues for designing anode materials. Furthermore, a large number of spin-polarized electrons were stored in the already-reduced Fe species.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'/%3e%3cpath fill='%23fff' d='m8.751-17.959 10.11 11.373L3.997-9.844l13.94-6.1-7.692 13.129z'/%3e%3c/svg%3e)
