  We estimate the modification of quarkonia yields due to different processes
in the medium produced in Pb+Pb collisions at LHC energy. The quarkonia and
heavy flavour cross sections calculated up to next-to-leading order (NLO) are
used in the study. Shadowing corrections are obtained with the NLO EPS09
parametrization. A kinetic model is employed which incorporates quarkonia
suppression inside a QGP, suppression due to hadronic comovers, and
regeneration from charm pairs. The quarkonia dissociation cross section due to
gluon collisions has been considered and the regeneration rate has been
obtained using the principle of detailed balance. The modification in quarkonia
yields due to collisions with hadronic comovers has been estimated assuming
that the comovers are pions. The manifestations of these effects on the nuclear
modification factors for both $J/\psi$ and $\Upsilon$ in different kinematic
regions has been demonstrated for Pb+Pb collisions at $\sqrt{s_{_{NN}}}$ = 2.76
TeV in comparison with the measurements. Both the suppression and regeneration
due to a deconfined medium strongly affect the low and intermediate $p_T$
range. The large observed suppression of $J/\psi$ at $p_T~>$ 10 GeV/$c$ exceeds
the estimates of suppression by gluon dissociation.
