Evidence of a J/ψΛ structure and observation of excited Ξ- states in the Ξb -→J/ψΛK- decay

LHCb Collaboration

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141 Citations (Scopus)


First evidence of a structure in the J/ψΛ invariant mass distribution is obtained from an amplitude analysis of Ξb -→J/ψΛK- decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8±2.9-1.1 +4.7MeV and 17.3±6.5-5.7 +8.0MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Ξ- states, Ξ1690- and Ξ1820-, are seen for the first time in a Ξb - decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb-1, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.

Original languageEnglish
Pages (from-to)1278-1287
Number of pages10
JournalScience Bulletin
Issue number13
Publication statusPublished - 15 Jul 2021


  • Exotics
  • Particle and resonance production
  • Pentaquark
  • QCD
  • Quarkonium
  • Spectroscopy


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