arXiv · 1712.03612
Observation of $Ξ_{c}(2930)^0$ and updated measurement of $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ at Belle
Abstract
We report the first observation of the $Ξ_{c}(2930)^0$ charmed-strange baryon with a significance greater than 5$σ$. The $Ξ_{c}(2930)^0$ is found in its decay to $K^- Λ_{c}^+$ in $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ decays. The measured mass and width are $[2928.9 \pm 3.0(\rm stat.)^{+0.9}_{-12.0}(\rm syst.)]$ MeV/$c^{2}$ and $[19.5 \pm 8.4(\rm stat.) ^{+5.9}_{-7.9}(\rm syst.)]$ MeV, respectively, and the product branching fraction is ${\cal B}(B^{-} \to Ξ_{c}(2930)^0 \barΛ_{c}^{-}) {\cal B}(Ξ_{c}(2930)^0 \to K^- Λ_{c}^{+})=[1.73 \pm 0.45(\rm stat.) \pm 0.21(\rm syst.)]\times 10^{-4}$. We also measure ${\cal B}(B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}) = [4.80 \pm 0.43(\rm stat.) \pm 0.60(\rm syst.)] \times 10^{-4}$ with improved precision, and search for the charmonium-like state $Y(4660)$ and its spin partner, $Y_η$, in the $Λ_{c}^{+}\barΛ_{c}^{-}$ invariant mass spectrum. No clear signals of the $Y(4660)$ nor its spin partner are observed and the 90\% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $(772\pm11)\times 10^{6} B\bar{B}$ pairs collected at the $Υ(4S)$ resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.
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Belle Collaboration, Y. B. Li, C. P. Shen, I. Adachi, J. K. Ahn, H. Aihara, S. Al Said, D. M. Asner, T. Aushev, R. Ayad, V. Babu, I. Badhrees, A. M. Bakich, Y. Ban, V. Bansal, P. Behera, M. Berger, V. Bhardwaj, B. Bhuyan, J. Biswal, G. Bonvicini, A. Bozek, M. Bračko, T. E. Browder, D. Červenkov, V. Chekelian, A. Chen, B. G. Cheon, K. Chilikin, K. Cho, S. -K. Choi, Y. Choi, D. Cinabro, S. Cunliffe, N. Dash, S. Di Carlo, Z. Doležal, Z. Drásal, S. Eidelman, D. Epifanov, J. E. Fast, T. Ferber, B. G. Fulsom, R. Garg, V. Gaur, N. Gabyshev, A. Garmash, M. Gelb, A. Giri, P. Goldenzweig, E. Guido, J. Haba, T. Hara, K. Hayasaka, H. Hayashii, M. T. Hedges, W. -S. Hou, T. Iijima, K. Inami, G. Inguglia, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, W. W. Jacobs, S. Jia, Y. Jin, K. K. Joo, T. Julius, G. Karyan, Y. Kato, T. Kawasaki, H. Kichimi, C. Kiesling, D. Y. Kim, J. B. Kim, K. T. Kim, S. H. Kim, K. Kinoshita, P. Kodyš, S. Korpar, D. Kotchetkov, P. Križan, R. Kroeger, P. Krokovny, R. Kulasiri, T. Kumita, A. Kuzmin, Y. -J. Kwon, I. S. Lee, S. C. Lee, L. K. Li, L. Li Gioi, J. Libby, D. Liventsev, M. Lubej, T. Luo, J. MacNaughton, M. Masuda, T. Matsuda. 2018-09-06. Observation of $Ξ_{c}(2930)^0$ and updated measurement of $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ at Belle. https://doi.org/10.1140/epjc%2Fs10052-018-5720-5
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