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  • Observation of two new $\Xi_b^-$ baryon resonances
    Andreotti, M; Baesso, C; Barlow, R. J; Barsuk, S; Belogurov, S; Bien, A; Blusk, S; Bondar, N; Bowcock, T. J. V; Brett, D; Brook, N. H; Charpentier, Ph; Closier, J; Coco, V; Cogneras, E; Collazuol, G; Contu, A; Crocombe, A. C; De Bruyn, K; De Silva, W; Di Domenico, A; Egorychev, V; Evans, H. -M; Fiorini, M; Firlej, M; Forty, R; Gaspar, C; Gavardi, L; Gazzoni, G; Gersabeck, M; Giubega, L; Golutvin, A; Diaz, R. Graciani; Gregson, S; Hadjivasiliou, C; Hall, S; Jacobsson, R; Jaton, P; Jing, F; Johnson, D; Kandybei, S; Kanso, W; Khurewathanakul, C; Korolev, M; Kruse, F; Kudryavtsev, V; Langenbruch, C; Lazzeroni, C; Gac, R. Le; Liles, M; Lucchesi, D; Lupato, A; Lupton, O; Manca, G; Matev, R; Moggi, N; Morawski, P; Mordà, A; Müller, K; Nasteva, I; Neufeld, N; Niess, V; Novoselov, A; Goicochea, J. M. Otalora; Otto, A; Oyanguren, A; Papanestis, A; Pearce, A; Penso, G; Pistone, A; Popov, D; Pritchard, A; Rakotomiaramanana, B; Raniuk, I; Reis, A. C. dos; Rihl, M; Rinnert, K; Robbe, P; Rodrigues, A. B; Sagidova, N; Santacesaria, R; Schiller, M; Sciascia, B; Shapkin, M; Stahl, M; Swientek, S; Thomas, C; Uwer, U; Vecchi, S; Vieira, D; Voß, C; Wandernoth, S; Whitehead, M; Wilschut, H. W; Wyllie, K; Xu, Z; Yushchenko, O; Zangoli, M; Zhang, Y; Zhokhov, A

    11/2014
    Journal Article

    Phys. Rev. Lett. 114, 062004 (2015) Two structures are observed close to the kinematic threshold in the $\Xi_b^0 \pi^-$ mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$ recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content $bds$ are expected in this mass region: the spin-parity $J^P = \frac{1}{2}^+$ and $J^P=\frac{3}{2}^+$ states, denoted $\Xi_b^{\prime -}$ and $\Xi_b^{*-}$. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be $m(\Xi_b^{\prime -}) - m(\Xi_b^0) - m(\pi^{-}) = 3.653 \pm 0.018 \pm 0.006$ MeV$/c^2$, $m(\Xi_b^{*-}) - m(\Xi_b^0) - m(\pi^{-}) = 23.96 \pm 0.12 \pm 0.06$ MeV$/c^2$, $\Gamma(\Xi_b^{*-}) = 1.65 \pm 0.31 \pm 0.10$ MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of $\Gamma(\Xi_b^{\prime -}) < 0.08$ MeV at 95% confidence level. Relative production rates of these states are also reported.

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