Measurement of nuclear modification factors of $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) mesons in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV

Bakhshiansohi, Hamed;Bondu, Olivier;Brochet, Sébastien;Bruno, Giacomo;CMS Collaboration;et.al.
(2019) Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics — Vol. B790, p. 270-293 (2019)

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Authors
  • Bakhshiansohi, HamedUCLouvain
    Author
  • Bondu, OlivierUCLouvain
    Author
  • Brochet, SébastienUCLouvain
    Author
  • Bruno, GiacomoUCLouvain
    Author
  • Caputo, ClaudioUCLouvain
    Author
  • Caudron, AdrienUCLouvain
    Author
  • David, PieterUCLouvain
    Author
  • De Visscher, SimonUCLouvain
    Author
  • Delaere, Christopheorcid-logoUCLouvain
    Author
  • Delcourt, MartinUCLouvain
    Author
  • François, BrieucUCLouvain
    Author
  • Giammanco, Andreaorcid-logoUCLouvain
    Author
  • Krintiras, GeorgiosUCLouvain
    Author
  • Lemaitre, VincentUCLouvain
    Author
  • Magitteri, AlessioUCLouvain
    Author
  • Mertens, AlexandreUCLouvain
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  • Musich, MarcoUCLouvain
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  • Piotrzkowski, KrzysztofUCLouvain
    Author
  • Quertenmont, LoïcUCLouvain
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  • Saggio, AlessiaUCLouvain
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  • Vidal Marono, MiguelUCLouvain
    Author
  • Wertz, SébastienUCLouvain
    Author
  • Zobec, JozeUCLouvain
    Author
  • CMS Collaboration
    Author
  • et. al.
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Abstract
The cross sections for $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, R$_\mathrm{AA}$, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, R$_\mathrm{AA}$($\Upsilon$(1S)) $>$ R$_\mathrm{AA}$($\Upsilon$(2S)) $>$ R$_\mathrm{AA}$($\Upsilon$(3S)) . The suppression of $\Upsilon$(1S) is larger than that seen at $\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the R$_\mathrm{AA}$ of $\Upsilon$(3S) integrated over $p_\mathrm{T}$ and rapidity is 0.094 at 95% confidence level, which is the strongest suppression observed for any hadron species in heavy ion collisions to date.
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Bakhshiansohi, H., Bondu, O., Brochet, S., Bruno, G., Caputo, C., Caudron, A., David, P., De Visscher, S., Delaere, C., Delcourt, M., François, B., Giammanco, A., Krintiras, G., Lemaitre, V., Magitteri, A., Mertens, A., Musich, M., Piotrzkowski, K., Quertenmont, L., et al. (2019). Measurement of nuclear modification factors of $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) mesons in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV. Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics, B790, 270-293. https://doi.org/10.1016/j.physletb.2019.01.006 (Original work published 2019)