Photoproduction of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi></mml:math>-even quarkonia at the EIC and EicC
Yu Jia, Zhewen Mo, Jichen Pan, Jia-Yue Zhang
Abstract
The ${\ensuremath{\eta}}_{c}$ photoproduction in $ep$ collision has long been proposed as an ideal process to probe the existence of Odderon. In the current work, we systematically investigate the photoproduction of various $C$-even heavy quarkonia (exemplified by ${\ensuremath{\eta}}_{c(b)}$, and ${\ensuremath{\chi}}_{c(b)J}$ with $J=0$, 1, 2) via one-photon exchange channel, at the lowest order in ${\ensuremath{\alpha}}_{s}$ and heavy quark velocity in the context of Non-relativistic quantum chromodynamics (NRQCD) factorization. We find that the photoproduction rates of ${\ensuremath{\eta}}_{c}$ through this mechanism are comparable in magnitude with that through the Odderon-initiated mechanism, even in the Regge limit ($s\ensuremath{\gg}\ensuremath{-}t$), though the latter types of predictions suffer from considerable theoretical uncertainties. The future measurements of these types of quarkonium photoproduction processes in EIC and EicC are crucial to ascertain which mechanism plays the dominant role.