Observation of J/ψp resonances consistent with pentaquark states in Λ0b → J/ψK-p decays

LHCb Collaboration, R. Aaij, B. Adeva, M. Adinolfi, A. Affolder, Z. Ajaltouni, S. Akar, J. Albrecht, F. Alessio, M. Alexander, S. Ali, G. Alkhazov, P. Alvarez Cartelle, A. A. Alves, S. Amato, S. Amerio, Y. Amhis, L. An, L. Anderlini, J. AndersonG. Andreassi, M. Andreotti, J. E. Andrews, R. B. Appleby, O. Aquines Gutierrez, F. Archilli, P. D'Argent, A. Artamonov, M. Artuso, E. Aslanides, G. Auriemma, M. Baalouch, S. Bachmann, J. J. Back, A. Badalov, C. Baesso, W. Baldini, R. J. Barlow, C. Barschel, S. Barsuk, S. Bifani, N. Farley, P. Griffith, P. Ilten, I. R. Kenyon, C. Lazzeroni, A. Mazurov, J. McCarthy, L. Pescatore, D. Popov, N. K. Watson

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Abstract

Observations of exotic structures in the J/ψp channel, which we refer to as charmonium-pentaquark states, in Λ0→ J/ψK-p decays are presented. The data sample corresponds to an integrated luminosity of 3 fb-1 acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis of the three-body final state reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380±8±29MeV and a width of 205±18±86MeV, while the second is narrower, with a mass of 4449.8±1.7±2.5MeV and a width of 39±5±19MeV. The preferred JP assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.

Original languageEnglish
Article number072001
Number of pages15
JournalPhysical Review Letters
Volume115
Issue number7
DOIs
Publication statusPublished - 12 Aug 2015

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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