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arXiv · 1808.08253

Comment on "$η_c$ production in photon-induced interactions at the LHC"

Spencer R. Klein
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Abstract

In "$η_c$ production in photon-induced interactions at the LHC," \cite{Goncalves:2018yxc} Goncalves and Moreira discuss inclusive and exclusive $η_c$ production at $pp$ and $pA$ collisions at LHC energies. The exclusive channels are via two-photon and photon-Odderon interactions. This comment points out that there is a large additional source of almost-exclusive $η_c$ in ultra-peripheral collisions: from the radiative decay of $J/ψ$ that are produced in photon-nucleon interactions. Although the $J/ψ\rightarrowγη_c$ branching ratio is small, the $J/ψ$ production cross-section is large enough that it dominates over the exclusive channels considered in \cite{Goncalves:2018yxc}, and is comparable to the non-exclusive production. In $J/ψ\rightarrowγη_c$, the photon is very soft and therefore easy to miss, and the $η_c$ will have very similar kinematics to the $J/ψ$.

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Spencer R. Klein. 2018-08-24. Comment on "$η_c$ production in photon-induced interactions at the LHC". https://doi.org/10.1103/physrevd.98.118501

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