Measurement of the ηc(1S) production cross-section in proton–proton collisions via the decay ηc(1S) → pp-

LHCb Collaboration, R. Aaij, C. Abellán Beteta, 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. AnderliniJ. Anderson, R. Andreassen, M. Andreotti, J. E. Andrews, R. B. Appleby, O. Aquines Gutierrez, F. Archilli, 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. Bifani, N. Farley, P. Griffith, P. Ilten, I. R. Kenyon, C. Lazzeroni, A. Mazurov, J. McCarthy, C. J. Parkinson, L. Pescatore, D. Popov, N. K. Watson

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The production of the ηc(1S) state in proton-proton collisions is probed via its decay to the pp- final state with the LHCb detector, in the rapidity range 2.0 < y < 4.5 and in the meson transverse-momentum range pT > 6.5 GeV/c. The cross-section for prompt production of ηc(1S) mesons relative to the prompt J/ψ cross-section is measured, for the first time, to be σηc(1S)J/ψ = 1.74±0.29±0.28±0. 18B at a centre-of-mass energy √s=7 TeV using data corresponding to an integrated luminosity of 0.7 fb-1, and σηc(1S)/σJ/ψ = 1.60±0.29±0.25±0.17B at √s=8 TeV using 2.0 fb-1. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the ηc(1S) and J/ψ decays to the pp- final state. In addition, the inclusive branching fraction of b-hadron decays into ηc(1S) mesons is measured, for the first time, to be B(b→ηcX)=(4.88±0.64±0.29±0.67B10-3, where the third uncertainty includes also the uncertainty on the J/ψ inclusive branching fraction from b-hadron decays. The difference between the J/ψ and ηc(1S) meson masses is determined to be 114.7±1.5±0.1MeV/c2.

Original languageEnglish
Article number311
Number of pages12
JournalEuropean Physical Journal C
Issue number7
Publication statusPublished - 4 Jul 2015


  • Transverse Momentum
  • Systematic Uncertainty
  • Kinematic Region
  • Uncertainty Component
  • Hadron Decay

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Physics and Astronomy (miscellaneous)


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