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Inclusive prompt $χ_{c,b}(1^{++})$ production at the LHC

We study the prompt production of the $χ_c(1^+)$ and $χ_b(1^+)$ mesons at high energies. Unlike $χ(0^+,2^+)$ production, $χ(1^+)$ mesons cannot be created at LO via the fusion of two on-mass-shell gluons, that is $gg\toχ_{c,b}(1^+)$ are not allowed. However, the available experimental data show that the cross sections for $χ_c(1^+)$ and $χ_c(2^+)$ are comparable. We therefore investigate four other $χ(1^+)$ production mechanisms: namely, (i) the standard NLO process $gg\toχ_{c,b}(1^+)+g$, (ii) via gluon virtuality, (iii) via gluon reggeization and, finally, (iv) the possibility to form $χ_{c,b}(1^+)$ by the fusion of three gluons, where one extra gluon comes from another parton cascade, as in the Double Parton Scattering processes.