Observation of $$\Xi _{c}(2930)^0$$ Ξc(2930)0 and updated measurement of $$B^{-} \rightarrow K^{-} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}$$ B-→K-Λc+Λ¯c- at Belle

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2018-03, Vol.78 (3), p.1-8
• Main Authors: 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, M. Merola
• Format: Article
• Language: English
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-018-5720-5

Abstract We report the first observation of the $$\Xi _{c}(2930)^0$$ Ξc(2930)0 charmed-strange baryon with a significance greater than 5$$\sigma $$ σ . The $$\Xi _{c}(2930)^0$$ Ξc(2930)0 is found in its decay to $$K^- \Lambda _{c}^+$$ K-Λc+ in $$B^{-} \rightarrow K^{-} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}$$ B-→K-Λc+Λ¯c- decays. The measured mass and width are $$[2928.9 \pm 3.0(\mathrm stat.)^{+0.9}_{-12.0}(\mathrm syst.)]$$ [2928.9±3.0(stat.)-12.0+0.9(syst.)]  MeV/$$c^{2}$$ c2 and $$[19.5 \pm 8.4(\mathrm stat.) ^{+5.9}_{-7.9}(\mathrm syst.)]$$ [19.5±8.4(stat.)-7.9+5.9(syst.)]  MeV, respectively, and the product branching fraction is $$\mathcal{B}(B^{-} \rightarrow \Xi _{c}(2930)^0 \bar{\Lambda }_{c}^{-}) \mathcal{B}(\Xi _{c}(2930)^0 \rightarrow K^- \Lambda _{c}^{+})=[1.73 \pm 0.45(\mathrm stat.) \pm 0.21(\mathrm syst.)]\times 10^{-4}$$ B(B-→Ξc(2930)0Λ¯c-)B(Ξc(2930)0→K-Λc+)=[1.73±0.45(stat.)±0.21(syst.)]×10-4 . We also measure $$\mathcal{B}(B^{-} \rightarrow K^{-} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}) = [4.80 \pm 0.43(\mathrm stat.) \pm 0.60(\mathrm syst.)] \times 10^{-4}$$ B(B-→K-Λc+Λ¯c-)=[4.80±0.43(stat.)±0.60(syst.)]×10-4 with improved precision, and search for the charmonium-like state Y(4660) and its spin partner, $$Y_{\eta }$$ Yη , in the $$\Lambda _{c}^{+}\bar{\Lambda }_{c}^{-}$$ Λc+Λ¯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 $$(772\pm 11)\times 10^{6} B\bar{B}$$ (772±11)×106BB¯ pairs collected at the $$\Upsilon (4S)$$ Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron–positron collider.