Abstract
The elliptic flow of prompt and non-prompt J/psi was measured in the dimuon decay channel in Pb+Pb collisions at sqrt{s_{_text {NN}}}=5.02 text {TeV} with an integrated luminosity of 0.42~mathrm {nb}^{-1} with the ATLAS detector at the LHC. The prompt and non-prompt signals are separated using a two-dimensional simultaneous fit of the invariant mass and pseudo-proper decay time of the dimuon system from the J/psi decay. The measurement is performed in the kinematic range of dimuon transverse momentum and rapidity 9<p_mathrm {T}<30 text {GeV}, |y|<2, and 0–60% collision centrality. The elliptic flow coefficient, v_2, is evaluated relative to the event plane and the results are presented as a function of transverse momentum, rapidity and centrality. It is found that prompt and non-prompt J/psi mesons have non-zero elliptic flow. Prompt J/psi v_2 decreases as a function of p_mathrm {T}, while for non-prompt J/psi it is, with limited statistical significance, consistent with a flat behaviour over the studied kinematic region. There is no observed dependence on rapidity or centrality.
Highlights
A complementary and powerful probe into the heavyquark flavour dependence of interaction mechanisms can be obtained by studying the azimuthal asymmetries of prompt and non-prompt quarkonia
A flavour-dependent enhancement of the azimuthal asymmetry of J/ψ at low pT can be interpreted as a difference in the degree of recombination between c- and b-quarks and it is expected that any flavour dependence will vanish at higher values of pT, which are accessible by this measurement
This paper provides v2 measurements as a function of transverse momentum, rapidity and collision centrality for both prompt and non-prompt J/ψ in the dimuon decay channel, extending the kinematic range covered by recent results from other LHC experiments [3,4,5]
Summary
A complementary and powerful probe into the heavyquark flavour dependence of interaction mechanisms can be obtained by studying the azimuthal asymmetries of prompt and non-prompt quarkonia. The observed azimuthal asymmetry for prompt J/ψ is the same in central collisions as in non-central collisions [5], for inclusive J/ψ some indication of the centrality dependence is reported in the lower pT region at forward rapidities at 5.02 TeV [4] and at 2.76 TeV [3] This is in contradiction with the expected hydrodynamic behaviour, which is confirmed by the results for charged hadrons where the anisotropies are more significant in semi-central collisions than in peripheral and central collisions [14,15,16,17,18]. This paper provides v2 measurements as a function of transverse momentum, rapidity and collision centrality for both prompt and non-prompt J/ψ in the dimuon decay channel, extending the kinematic range covered by recent results from other LHC experiments [3,4,5]
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