Li Y B, Shen C P, Adachi I, Adamczyk K, Aihara H, Al Said S, Asner D M, Aushev T, Ayad R, Babu V, Behera P, Bennett J, Bessner M, Bhardwaj V, Bhuyan B, Bilka T, Biswal J, Bonvicini G, Bozek A, Bračko M, Browder T E, Campajola M, Červenkov D, Chang M-C, Chen A, Cheon B G, Chilikin K, Cho K, Cho S-J, Choi S-K, Choi Y, Choudhury S, Cinabro D, Cunliffe S, Das S, Dash N, De Nardo G, Dhamija R, Di Capua F, Dong T V, Eidelman S, Epifanov D, Ferber T, Fulsom B G, Garg R, Gaur V, Gabyshev N, Garmash A, Giri A, Goldenzweig P, Grzymkowska O, Gudkova K, Hadjivasiliou C, Hartbrich O, Hayasaka K, Hayashii H, Hernandez Villanueva M, Hsu C-L, Ishikawa A, Itoh R, Iwasaki M, Iwasaki Y, Jacobs W W, Jia S, Jin Y, Joo C W, Joo K K, Kang K H, Karyan G, Kato Y, Kichimi H, Kim C H, Kim D Y, Kim K-H, Kim S H, Kinoshita K, Kodyš P, Konno T, Korobov A, Korpar S, Kovalenko E, Križan P, Kroeger R, Krokovny P, Kuhr T, Kumar M, Kumar R, Kumara K, Kuzmin A, Kwon Y-J, Lalwani K, Lange J S, Lee I S, Lee S C, Li C H, Li L K, Li Gioi L, Libby J, Lieret K, Liventsev D, Masuda M, Matvienko D, McNeil J T, Metzner F, Mizuk R, Mohanty G B, Moon T J, Mori T, Mussa R, Natochii A, Nayak L, Nayak M, Niiyama M, Nisar N K, Nishida S, Nishimura K, Ogawa S, Ono H, Onuki Y, Pakhlov P, Pakhlova G, Pang T, Pardi S, Park H, Patra S, Paul S, Pedlar T K, Pestotnik R, Piilonen L E, Podobnik T, Popov V, Prencipe E, Prim M T, Röhrken M, Rostomyan A, Rout N, Russo G, Sahoo D, Sakai Y, Sandilya S, Santelj L, Sanuki T, Savinov V, Schnell G, Schwanda C, Seino Y, Senyo K, Shapkin M, Sharma C, Shiu J-G, Sokolov A, Solovieva E, Starič M, Stottler Z S, Sumihama M, Tamponi U, Tanida K, Tenchini F, Uchida M, Uehara S, Uglov T, Uno K, Uno S, Usov Y, Van Tonder R, Varner G, Vinokurova A, Vossen A, Wang C H, Wang M-Z, Wang P, Wang X L, Watanabe M, Watanuki S, Won E, Xu X, Yan W, Yang S B, Ye H, Yin J H, Yuan C Z, Zhang Z P, Zhilich V, Zhukova V
Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443.
SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193.
Phys Rev Lett. 2021 Sep 17;127(12):121803. doi: 10.1103/PhysRevLett.127.121803.
Using data samples of 89.5 and 711 fb^{-1} recorded at energies of sqrt[s]=10.52 and 10.58 GeV, respectively, with the Belle detector at the KEKB e^{+}e^{-} collider, we report measurements of branching fractions of semileptonic decays Ξ_{c}^{0}→Ξ^{-}ℓ^{+}ν_{ℓ} (ℓ=e or μ) and the CP-asymmetry parameter of Ξ_{c}^{0}→Ξ^{-}π^{+} decay. The branching fractions are measured to be B(Ξ_{c}^{0}→Ξ^{-}e^{+}ν_{e})=(1.31±0.04±0.07±0.38)% and B(Ξ_{c}^{0}→Ξ^{-}μ^{+}ν_{μ})=(1.27±0.06±0.10±0.37)%, and the decay parameter α_{Ξπ} is measured to be 0.63±0.03±0.01 with much improved precision compared with the current world average. The corresponding ratio B(Ξ_{c}^{0}→Ξ^{-}e^{+}ν_{e})/B(Ξ_{c}^{0}→Ξ^{-}μ^{+}ν_{μ}) is 1.03±0.05±0.07, which is consistent with the expectation of lepton flavor universality. The first measured asymmetry parameter A_{CP}=(α_{Ξ^{-}π^{+}}+α_{Ξ[over ¯]^{+}π^{-}})/(α_{Ξ^{-}π^{+}}-α_{Ξ[over ¯]^{+}π^{-}})=0.024±0.052±0.014 is found to be consistent with zero. The first and the second uncertainties above are statistical and systematic, respectively, while the third ones arise due to the uncertainty of the Ξ_{c}^{0}→Ξ^{-}π^{+} branching fraction.
利用在KEKB正负电子对撞机上的 Belle 探测器，分别在质心能量(\sqrt{s}=10.52)GeV 和(10.58)GeV 下记录的(89.5)和(711) (fb^{-1})的数据样本，我们报告了半轻子衰变(\Xi_{c}^{0}\to\Xi^{-}\ell^{+}\nu_{\ell})（(\ell = e)或(\mu)）的分支比以及(\Xi_{c}^{0}\to\Xi^{-}\pi^{+})衰变的 CP 不对称参数的测量结果。测得的分支比为(B(\Xi_{c}^{0}\to\Xi^{-}e^{+}\nu_{e})=(1.31\pm0.04\pm0.07\pm0.38)%)和(B(\Xi_{c}^{0}\to\Xi^{-}\mu^{+}\nu_{\mu})=(1.27\pm0.06\pm0.10\pm0.37)%)，并且测得衰变参数(\alpha_{\Xi\pi})为(0.63\pm0.03\pm0.01)，与当前世界平均值相比精度有了很大提高。相应的比值(B(\Xi_{c}^{0}\to\Xi^{-}e^{+}\nu_{e})/B(\Xi_{c}^{0}\to\Xi^{-}\mu^{+}\nu_{\mu}))为(1.03\pm0.05\pm0.07)，这与轻子味普适性的预期一致。首次测量的不对称参数(A_{CP}=(\alpha_{\Xi^{-}\pi^{+}}+\alpha_{\overline{\Xi}^{+}\pi^{-}})/(\alpha_{\Xi^{-}\pi^{+}}-\alpha_{\overline{\Xi}^{+}\pi^{-}})=0.024\pm0.052\pm0.014)被发现与零一致。上述第一个和第二个不确定度分别是统计不确定度和系统不确定度，而第三个不确定度是由于(\Xi_{c}^{0}\to\Xi^{-}\pi^{+})分支比的不确定性引起的。
