Study of $\psi(2S)$ production and cold nuclear matter effects in $p$Pb collisions at $\sqrt {s_{NN}} = 5$ TeV

The production of $\psi(2S)$ mesons is studied in dimuon final states using proton-lead collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of $1.6~\mathrm{nb}^{-1}$. The nucleon-nucleon centre-of-mass energy of the proton-lead collisions is $\sqrt{s_{NN}}=5~\mathrm{TeV}$. The measurement is performed using $\psi(2S)$ mesons with transverse momentum less than $14~\mathrm{GeV}/c$ and rapidity $y$ in the ranges 1.5 < $y$ < 4.0 and -5.0 < $y$ <-2.5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for $\psi(2S)$ mesons. Using the production cross-section results of $\psi(2S)$ and $J/\psi$ mesons from $b$-hadron decays, the $b\bar{b}$ cross-section in $p$Pb collisions at $\sqrt{s_{NN}}=5~\mathrm{TeV}$ is obtained.