PoS - Proceedings of Science
Volume 390 - 40th International Conference on High Energy physics (ICHEP2020) - Parallel: Strong Interactions and Hadron Physics
Production of $\eta_c(1S,2S)$ in $\e^+ e^-$ and $p p$ collisions
I. Babiarz,* W. Schäfer, A. Szczurek
*corresponding author
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Pre-published on: February 13, 2021
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We derive the light-front wave function (LFWF) representation of the $\gamma^{*} \gamma^{*} \to \eta_{c} (1S),\eta_{c}(2S)$ transition form factor $F(Q^2_1,Q^2_2)$ for two virtual photons in the initial state. For the LFWF, we use different models obtained from the solution of the Schroedinger equation for a variety of $c\bar{c}$ potentials. We compare our results to the BaBar experimental data for the $\eta_{c}(1S)$ transition form factor, for one real and one virtual photon. We observe that the onset of the asymptotic behaviour is strongly delayed and discuss applicability of the collinear and/or massless limit.
In addition, we present a thorough analysis of $\eta_{c}(1S,2S)$ quarkonia hadroproduction in $k_{\perp}$-factorisation in the framework of the light-front potential approach for the quarkonium wave function. The off-shell matrix elements for the $g^{∗} g^{∗} \to \eta_{c} (1S,2S)$ vertices are derived. We discuss the importance of taking into account the gluon virtualities. We present the transverse momentum distributions of $\eta_c$ for several models of the unintegrated gluon distributions. Our calculations are performed for four distinct parameterisations for the $c\bar{c}$ interaction potential consistent with the meson spectra. We compare our results for $\eta_{c}(1S)$ to measurements by the LHCb collaboration and present predictions for $\eta_{c}(2S)$ production.
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