May 13 – 19, 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

Quarkonium Production and Polarization in an Improved Color Evaporation Model

May 16, 2018, 5:50 PM
20m
Sala Mosaici-2, 3rd Floor (Palazzo del Casinò)

Sala Mosaici-2, 3rd Floor

Palazzo del Casinò

Parallel Talk Quarkonia Quarkonia

Speaker

Ramona Vogt (LLNL)

Description

An improved version of the color evaporation model (ICEM) has been introduced to describe heavy quarkonium production [1]. In contrast to the traditional color evaporation model, the constraint was imposed that the invariant mass of the intermediate heavy quark-antiquark pair must be larger than the mass of produced quarkonium. A momentum shift between heavy quark-antiquark pair and the quarkonium was also introduced. Calculations show that the model can describe the charmonium yields as well as ratio of $\psi^\prime$ over $J/\psi$ better than the traditional color evaporation model.

The ICEM has been extended to calculate the polarization of prompt $J/\psi$ and $\Upsilon$(1S) production for the first time in the color evaporation approach. The first calculations were made at leading order. The polarization parameter $\lambda_\vartheta$ was calculated as a function of center of mass energy and rapidity in $p+p$ collisions. The $x_F$ dependence of the polarization was also calculated and compared to experimental results in $p$+Cu and $\pi$+W collisions [2,3]. The next step of calculating the $p_T$ dependence of the polarization has been taken, with a calculation in the $k_T$-factorization approach [4].

This talk will compare the unpolarized $p_T$ distributions for the $J/\psi$ and $\psi'$, as well as the $\psi'$ to $J/\psi$ ratio, in $p+p$ collisions at RHIC and the LHC for several energies. It will also present the polarization results and make comparison to polarization data from RHIC, the Tevatron and the LHC.

[1] Y.-Q. Ma and R. Vogt, Phys. Rev. D {\bf 94} (2016) 114029.

[2] V. Cheung and R. Vogt, Phys. Rev. D {\bf 95} (2017) 074021.

[3] V. Cheung and R. Vogt, Phys. Rev. D {\bf 96} (2017) 054014.

[4] V. Cheung and R. Vogt, in preparation.

Content type Theory
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