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Phys Rev Lett. 2024 Aug 16;133(7):071802. doi: 10.1103/PhysRevLett.133.071802.
We report the results of the first search for B^{-} decays to the Ξ[over ¯]{c}^{0}Λ[over ¯]{c}^{-} final state using 711 fb^{-1} of data collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The results are interpreted in terms of both direct baryon-number-violating B^{-} decay and Ξ_{c}^{0}-Ξ[over ¯]{c}^{0} oscillations which follow the standard model decay B^{-}→Ξ{c}^{0}Λ[over ¯]{c}^{-}. We observe no evidence for baryon number violation and set the 95% confidence-level upper limits on the ratio of baryon-number-violating and standard model branching fractions B(B^{-}→Ξ[over ¯]{c}^{0}Λ[over ¯]{c}^{-})/B(B^{-}→Ξ{c}^{0}Λ[over ¯]{c}^{-}) to be <2.7% and on the effective angular frequency of mixing ω in Ξ{c}^{0}-Ξ[over ¯]_{c}^{0} oscillations to be <0.76 ps^{-1} (equivalent to τ_{mix}>1.3 ps).
我们报告了首次使用KEKB非对称能量正负电子对撞机上的 Belle 探测器在 Υ(4S)共振处收集的711 fb⁻¹数据，对 B⁻衰变到 Ξ̅ₑ⁰Λ̅ₑ⁻末态进行搜索的结果。结果从直接违反重子数的 B⁻衰变以及遵循标准模型衰变 B⁻→Ξₑ⁰Λ̅ₑ⁻的 Ξₑ⁰ - Ξ̅ₑ⁰振荡两方面进行了解释。我们没有观察到重子数违反的证据，并设定了违反重子数与标准模型分支比 B(B⁻→Ξ̅ₑ⁰Λ̅ₑ⁻)/B(B⁻→Ξₑ⁰Λ̅ₑ⁻)的95%置信水平上限为<2.7%，以及 Ξₑ⁰ - Ξ̅ₑ⁰振荡中混合有效角频率ω的上限为<0.76 ps⁻¹（相当于τₘᵢₓ>1.3 ps）。
