Quarkonia suppression in PbPb collisions at $\sqrt{s_{NN}}=2.76$ TeV

We estimate the modification of quarkonia yields due to different processes in the medium produced in PbPb collisions at LHC energy. The quarkonia and heavy flavor 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 $\mathrm{{\rm Y}}$ in different kinematic regions has been demonstrated for PbPb 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 $p_T>10\text{GeV}/c$ exceeds the estimates of suppression by gluon dissociation.

Figure 1

(a) Temperature and (b) QGP fraction in the system as a function of proper time $\tau$ in case of the most central $\left(0–5\%\right)$ collisions for longitudinal and cylindrical expansions using first-order and lattice equation of state.

Figure 2

Gluon dissociation cross section of quarkonia as a function of gluon energy $\left(q^0\right)$ in quarkonia rest frame.

Figure 3

Gluon dissociation rate of $J/\psi$ as a function of (a) temperature and (b) transverse momentum.

Figure 4

Formation rate of $J/\psi$ as a function of (a) temperature and (b) transverse momentum.

Figure 5

Calculated nuclear modification factor $\left(R_{AA}\right)$ as a function of $J/\psi$ transverse momentum compared with (a) ALICE and (b) CMS measurements.

Figure 6

Calculated nuclear modification factor $\left(R_{AA}\right)$ compared with ALICE measurements at LHC.

Figure 7

Calculated nuclear modification factor $\left(R_{AA}\right)$ compared with (a) ALICE and (b) CMS measurements at midrapidity. The regeneration for the CMS high $p_T$ measurement is negligible in comparison to the low $p_T$ ALICE measurement.

Figure 8

Calculated nuclear modification factor $\left(R_{AA}\right)$ compared with CMS (a) $\mathrm{{\rm Y}}$(1S) and (b) $\mathrm{{\rm Y}}$(2S) measurements. Regeneration is assumed to be negligible.

Figure 9

Calculated nuclear modification factor $\left(R_{AA}\right)$ compared with ALICE $\mathrm{{\rm Y}}$(1S) measurement in forward rapidity.

Figure 10

Calculated nuclear modification factor $\left(R_{AA}\right)$ as a function of $\mathrm{{\rm Y}}$ transverse momentum.