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

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    The beta decay of the lightest charmed baryon.+ 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 Cabibbosuppressed decay Lambda(+) (c) -> ne(+)v(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) -> Lambda e(+)v(e), achieving a statistical significance exceeding 10s. The absolute branching fraction ismeasured to be (3.57 +/- 0.34(stat.)+/- 0.14(syst).) x 10(-3). For the first time, the CKM matrix element |V-cd| is extracted via a charmed baryon decay as 0:208 +/- 0:011(exp): +/- 0:007(LQCD) +/- 0:001 tau(+)(Lambda) (c). This work highlights a new approach to further understand fundamental interactions in the charmed baryon sector, and showcases the power ofmodernmachine learning techniques in experimental high-energy physics.LPHE-L
    Infoscience - École polytechnique fédérale de Lausanne
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale

    Measurement of Σ+ transverse polarization in e + e − collisions at s s \sqrt{s} = 3.68 − 3.71 GeV

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    Abstract Using e + e − collision data collected with the BESIII detector at seven energy points ranging from 3.68 to 3.71 GeV and corresponding to an integrated luminosity of 652.1 pb −1, we present an energy-dependent measurement of the transverse polarization, relative phase and modulus ratio of the electromagnetic form factors of the Σ+ hyperon in the e + e − → Σ + Σ ¯ − Σ+Σ‾− {\Sigma}^{+}{\overline{\Sigma}}^{-} reaction. At each energy point, no evident polarization is observed. These results are helpful to understand the production mechanism of the Σ+- Σ ¯ − Σ‾− {\overline{\Sigma}}^{-} pairs
    Infoscience - École polytechnique fédérale de Lausanne
    Directory of Open Access Journals
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale

    Search for a dark baryon in the Ξ−→π−+invisible decay

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    A search for a dark baryon is performed for the first time in the two-body decay Ξ−→π−+invisible using (10.087 ± 0.044) × 109 J / ψ events collected at a center-of-mass energy of s=3.097GeV with the BESIII detector at the BEPCII collider. No significant signal is observed, and the 90% (95%) confidence level upper limits on the branching fraction B(Ξ−→π−+invisible) are determined to be 4.2×10−5 (5.2×10−5), 6.9×10−5 (8.4×10−5), 6.5×10−4 (7.6×10−4), 1.1×10−4 (1.3×10−4) and 4.5×10−5 (5.5×10−5), under the dark baryon mass hypotheses of 1.07 GeV/ c 2, 1.10 GeV/ c 2, mΛ (1.116 GeV/ c 2), 1.13 GeV/ c 2, and 1.16 GeV/ c 2, respectively. The constraints obtained on the Wilson coefficients Cus,sL and Cus,sR are more stringent than the previous limits derived from the LHC searches for the colored mediators.LPHE-L
    Infoscience - École polytechnique fédérale de Lausanne
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale
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