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A. M. Sirunyan, A. Tumasyan, W. Adam, Janik Walter Andrejkovic, T. Bergauer, S. Chatterjee, M. Dragicevic, A. Escalante Del Valle, R. Frühwirth, M. Jeitler, N. Krammer, L. Lechner, D. Liko, I. Mikulec, F. M. Pitters, J. Schieck, R. Schöfbeck, M. Spanring, S. Templ, W. Waltenberger, C.-E. Wulz, V. Chekhovsky, A. Litomin, V. Makarenko, M. R. Darwish, E. A. De Wolf, X. Janssen, T. Kello, A. Lelek, H. Rejeb Sfar, P. Van Mechelen, S. Van Putte, N. Van Remortel, F. Blekman, E. S. Bols, J. D’Hondt, J. De Clercq, M. Delcourt, S. Lowette, S. Moortgat, A. Morton, D. R. Müller, A. R. Sahasransu, S. Tavernier, W. Van Doninck, P. Van Mulders, D. Beghin, B. Bilin, B. Clerbaux, G. De Lentdecker, L. Favart, A. Grebenyuk, A. K. Kalsi, K. Lee, M. Mahdavikhorrami, I. Makarenko, L. Moureaux, L. Pétré, A. Popov, N. Postiau, E. Starling, L. Thomas, M. Vanden Bemden, C. Vander Velde, P. Vanlaer, D. Vannerom, L. Wezenbeek, T. Cornelis, D. Dobur, M. Gruchala, Luka Lambrecht, G. Mestdach, M. Niedziela, C. Roskas, K. Skovpen, T. T. Tran, M. Tytgat, W. Verbeke, B. Vermassen, M. Vit, A. Bethani, G. Bruno, F. Bury, C. Caputo, P. David, C. Delaere, I. S. Donertas, A. Giammanco, K. Jaffel, V. Lemaitre, K. Mondal, J. Prisciandaro, A. Taliercio, M. Teklishyn, P. Vischia, S. Wertz, S. Wuyckens, G. A. Alves, C. Hensel, A. Moraes
Abstract
The ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass spectrum is investigated with an event sample of proton-proton collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$, collected by the CMS experiment at the LHC in 2016--2018 and corresponding to an integrated luminosity of $140\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The ground state ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ is reconstructed via its decays to ${J/\ensuremath{\psi}\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}$ and $J/\ensuremath{\psi}\mathrm{\ensuremath{\Lambda}}{K}^{\ensuremath{-}}$. A narrow resonance, labeled ${\mathrm{\ensuremath{\Xi}}}_{b}(6100{)}^{\ensuremath{-}}$, is observed at a ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass of $6100.3\ifmmode\pm\else\textpm\fi{}0.2(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.6({\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}})\text{ }\text{ }\mathrm{MeV}$, where the last uncertainty reflects the precision of the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ baryon mass. The upper limit on the ${\mathrm{\ensuremath{\Xi}}}_{b}(6100{)}^{\ensuremath{-}}$ natural width is determined to be $1.9\text{ }\text{ }\mathrm{MeV}$ at 95% confidence level. The low ${\mathrm{\ensuremath{\Xi}}}_{b}(6100{)}^{\ensuremath{-}}$ signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited ${\mathrm{\ensuremath{\Xi}}}_{c}$ baryon states, the new ${\mathrm{\ensuremath{\Xi}}}_{b}(6100{)}^{\ensuremath{-}}$ resonance and its decay sequence are consistent with the orbitally excited ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ baryon, with spin and parity quantum numbers ${J}^{P}=3/{2}^{\ensuremath{-}}$.