The production of the η c(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 p T > 6.5 GeV/c. The cross-section for prompt production of η c;(1S) mesons relative to the prompt J/ψ cross-section is measured, for the first time, to be σ ηc(1S)/σ J/ψ = 1.74±0.29±0.28±0. 18 B at a centre-of-mass energy (Formula presented.) using data corresponding to an integrated luminosity of 0.7 fb -1, and σ ηc(1S)/σJ/ψ = 1.60±0.29±0.25±0.17 B at (Formula presented.) using 2.0 fb -1. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the η c(1S) and J/ψ decays to the pp final state. In addition, the inclusive branching fraction of b-hadron decays into η c(1S) mesons is measured, for the first time, to be B(b→η cX)=(4.88±0.64±0.29±0.67 B)× 10-3, 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 η c(1S) meson masses is determined to be 114.7±1.5±0.1MeV/c 2.
Bibliographical noteFunding Information:
We would like to thank Emi Kou for motivating the studies of charmonium production in LHCb using hadronic final states and the useful discussions regarding charmonium production mechanisms. We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); NSFC (China); CNRS/IN2P3 (France); BMBF, DFG, HGF and MPG (Germany); SFI (Ireland); INFN (Italy); FOM and NWO (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES and FANO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). We are indebted to the communities behind the multiple open source software packages on which we depend. We are also thankful for the computing resources and the access to software R&D tools provided by Yandex LLC (Russia). Individual groups or members have received support from EPLANET, Marie Skłodowska-Curie Actions and ERC (European Union), Conseil général de Haute-Savoie, Labex ENIGMASS and OCEVU, Région Auvergne (France), RFBR (Russia), XuntaGal and GENCAT (Spain), Royal Society and Royal Commission for the Exhibition of 1851 (United Kingdom).
© 2015, CERN for the benefit of the LHCb collaboration.
All Science Journal Classification (ASJC) codes
- Engineering (miscellaneous)
- Physics and Astronomy (miscellaneous)