Forward J/$\psi$ $v_{2}$ extraction in 20-40% and $2<p_{T}<3$ GeV/c  in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}} }  = 5.02$ TeV

First, invariant mass spectra is used to obtained ration $ \alpha=$ S/(S+B). 

Then, a total fit on dimuon $v_{2}$ versus $m_{\mu\mu}$ following the formula $v_{2} = v_{2}^{bkg}(1-\alpha ) + v_{2}^{sig} \alpha$ gives in output the $v_{2}^{sig}$. 

Finally, the $\langle p_{T} \rangle$ of the signal is extracted using the fit on  $p_{T}$ versus $m_{\mu\mu}$.

Event mixing procedure is used to reproduce the background $v_{2}$ (here it is only plotted on the $v_{2}$ versus $m_{\mu\mu}$ )