$\psi(2S)$ and $J/\psi$ production in pp collisions at $\sqrt{s}$ = 7, 8 and 13 TeV

Authors: YASIR ALI, UZMA TABASSAM, SYED UZAIR AHMED SHAH, ATIF ARIF, MAIS SULEYMANOV, ZAIN UL ABIDIN

Abstract: Proton-proton collision is an essential part of high energy physics, as it is a baseline for nucleus-nucleus and hadron-nucleus collisions. Quark-gluon plasma, an exotic state of strongly interacting QCD matter, is routinely produced in heavy nuclei high-energy collisions. Charmonium, the bound states of $c\bar{c}$ produced at the early stages of collisions, are nice probes to examine the properties of matter through which they pass. The differential cross-sections of inclusive $\psi(2S)$ in pp collisions at energies of $\sqrt{s}$ = 7, 8 and 13 TeV have been studied. PYTHIA 8.1 event generator is used for the simulation of data. The differential cross-section of inclusive $J/\psi$ is also presented in order to examine the $\psi(2S)$ to $J/\psi$ ratio at similar energies. Both charmonium states are simulated in dimuon ($\mu^{+}\mu^{-}$) decay channel. The simulated data is also compared with the ALICE and LHCb experimental data based at LHC. We have plotted the differential cross-section as a function of transverse momentum ($p_T$) and rapidity $y$. PYTHIA simulation is found to be in good agreement with ALICE data for low $p_T$ interval, y interval close to midrapidity, while PYTHIA agrees with LHCb data at low $p_T$ interval. It is observed that the LHCb differential cross-section distributions of $J/\psi$ and $\psi(2S)$ as a function of y are lower compared to the ALICE data distributions and PYTHIA simulations. The $\psi(2S)$ to $J/\psi$ ratio is also well explained by PYTHIA and shows an increase in production of inclusive $J/\psi$ as compared to inclusive $\psi(2S)$.

Keywords: Quark-gluon plasma, charmonium, differential cross-section, transverse momentum, PYTHIA

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