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Measurement of Prompt $\psi(2S) \to J/\psi$ Yield Ratios in Pb-Pb and $p-p$ Collisions at $\sqrt {s_{NN}}=$ 2.76  TeV

The CMS collaboration
Phys.Rev.Lett. 113 (2014) 262301, 2014

Abstract (data abstract)
CERN-LHC. The ratio between the prompt psi(2S) and J/psi yields, reconstructed via their decays into muon pairs, is measured in lead-lead and proton-proton collisions at a centre-of-mass energy per nucleon-nucleon pair of 2.76 TeV. The analysis is based on lead-lead and proton-proton data samples collected by CMS at the LHC, corresponding to integrated luminosities of 150 mub^-1 and 5.4 pb^-1, respectively. The double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, is computed in three lead-lead collision centrality bins and two kinematic ranges: one at midrapidity, |y|<1.6, covering the transverse momentum range 6.5<pT<30 GeV/c, and the other at forward rapidity, 1.6<|y|<2.4, extending to lower pT values, 3<pT<30 GeV/c. The centrality-integrated double ratio changes from 0.45 +/- 0.13 (stat) +/- 0.07 (syst) in the first range to 1.67 +- 0.34 (stat) +- 0.27 (syst) in the second. This difference is most pronounced in the most central collisions.

  • Table 1

    Data from Figure 2

    10.17182/hepdata.66548.v1/t1

    Double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, as a function of centrality, for the midrapidity...

  • Table 2

    Data from Figure 2

    10.17182/hepdata.66548.v1/t2

    Double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, as a function of centrality, for the forward...

  • Table 3

    Data from Figure 2

    10.17182/hepdata.66548.v1/t3

    Double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, integrated over centrality, for the midrapidity and forward...

  • Table 4

    Data from Page 5 of preprint

    10.17182/hepdata.66548.v1/t4

    Nuclear modification factor RAA of psi(2S) integrated over centrality, for the midrapidity and forward rapidity analysis bins.

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