From transition electromagnetic form factors ${\gamma }^{\ast }{\gamma }^{\ast }{\eta }_c(1S,2S)$ to the production of ${\eta }_c(1S,2S)$ at the LHC

Abstract

We review our recent results for production of ${\eta }_c(1S)$ and ${\eta }_c(2S)$ in the ${\gamma }^{\ast }{\gamma }^{\ast }\to {\eta }_c(1S,2S)$ fusion and in proton-proton collisions via gluon-gluon fusion. The quarkonium wave functions are calculated by solving Schrödinger equation for different $c\bar{c}$ potentials. Using Terentev prescription the light-cone wave functions are obtained. The light-cone wave functions are used then to calculate ${\gamma }^{\ast }{\gamma }^{\ast }\to {\eta }_c$ transition form factors. The theoretical results are compared to the Belle experimental data for ${\eta }_c(1S)$. In addition we discuss our results for two-photon decay width. We present also results of our calculations for proton-proton collisions obtained within $k_T$-factorization approach for different unintegrated gluon distributions. The results for hadroproduction of ${\eta }_c(1S)$ are compared to the LHCb experimental data.

Comments: 15 pages, 14 figures, presentation at the XXVI Cracow EPIPHANY Conference, LHC Physics: Standard Model and Beyond, 7-10 January 2020}