Speaker
Description
Understanding $J/\psi$ meson hadroproduction has been a long-term effort both experimentally and theoretically. However, none of the existing theoretical models can successfully describe both $J/\psi$ transverse momentum ($p_{T}$) spectrum and the polarization. Furthermore, the composition of inclusive $J/\psi$ is complicated, including direct production via gluon fusion, parton fragmentation, and feed-down from excited charmonium states and B hadrons. Measurements of $J/\psi$ production at a different beam energy can shed new lights on the understanding of different $J/\psi$ production mechanisms, and help to constrain model calculations.
We report measurements of $J/\psi$ production in p+p collisions at $\sqrt{s}$ = 500 GeV in both the di-electron and di-muon channels. By combining measurements from these two channels, the $p_{T}$ spectrum of $J/\psi$ is measured from 0 to 20 GeV/$c$ and compared with NLO NRQCD and CGC+NRQCD calculations at different kinematic ranges. Feed-down contributions from $\psi(2S)$ is studied in the $p_{T}$ range of $4 < p_{T} < 12$ GeV/$c$. In addition, measurements of the $J/\psi$ production as a function of charged-particle multiplicity will be presented. A strong increase of the relative $J/\psi$ yield with multiplicity is observed for all $p_{T}$ bins with significant $p_{T}$ dependence. The results are compared with predications from the Percolation model and PYTHIA8
| Preferred Track | Quarkonia |
|---|---|
| Collaboration | STAR |
