Search for collectivity with azimuthal J/$\psi$-hadron correlations in high-multiplicity p-Pb collisions at $\sqrt{s}$ = 5.02 and 8.16 TeV

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5.02 TeV
8 TeV
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We present a measurement of angular correlations between inclusive \jpsi\ and charged
hadrons in p--Pb collisions with the ALICE detector at the CERN LHC. The \jpsi\ are reconstructed at forward (2.03 $<$ y $<$ 3.53) and
backward ($-$4.46 $<$ y $<$ $-$2.96) rapidity via their $\mu^+\mu^-$ decay channel while the charged hadrons are reconstructed at mid-rapidity
($-$1.8 $<$ $\eta$ $<$ 1.8). The correlations are expressed in terms of associated
charged-hadron yields per \jpsi\ trigger. A rapidity gap of at least 1.5 units between
the trigger \jpsi\ and the associated charged hadrons is required. Possible collective correlations are assessed by subtracting the
associated per-trigger yields in the low-multiplicity collisions from the ones in the high-multiplicity collisions.
After the subtraction we observe a strong indication of remaining symmetric structures at $\Delta\varphi$ $\approx$ 0 and $\Delta\varphi$ $\approx$ $\pi$,
similar to those previously found in two-particle correlations
at mid and forward rapidity. The corresponding second-order harmonic coefficient $v_2$ in the transverse momentum interval between 3 and 6 GeV/$c$
is found to be non-zero with a total significance of about 5$\sigma$.
The obtained results are similar to the $v_2$ coefficients measured in
Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02, suggesting a common mechanism at the origin of the \jpsi\ $v_2$.
Possible implications for the theoretical models of the J/$\psi$ production are discussed.