Two-gluon production of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>ϕ</mml:mi></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>η</mml:mi><mml:mo>′</mml:mo></mml:math> mesons in proton-proton collisions at high energies

We discuss gluon-gluon mechanisms for production of mesons with hidden strangeness, such as $\eta'$ and $\phi$ meson, in proton-proton collisions at large energies. The $g^* g^* \to \eta'$ \phi g$ are considered only the corresponding cross sections calculated $k_t$-factorization approach. $F_{\gamma^* \gamma^* \eta'}$ $F_{g^* form factors from quark-antiquark light-cone wave function including quark/antiquark transverse momenta. result two-photon transition factor demonstrates that higher twists may survive even to photon virtualities. is compared a recent leading-twist NLO analysis which uses phenomenological distribution amplitudes fitted exclusive $e^+ e^- e^+ reaction. calculate momentum distributions both RHIC LHC results experimental data whenever available. Lund string model shown comparison It seems two-gluon fusion not dominant mechanism production, although situation $\eta'$, especially larger energies, less clear due lack data.