Pair Production of Charmonia in the LHCb Experiment in the Parton Reggeization Approach

Pair production of prompt \(1S\) and \(2S\) charmonia states is studied in the improved color evaporation model using high energy factorization as formulated in the Parton Reggeization Approach. The latter is based on the modified Kimber–Martin–Ryskin–Watt model for unintegrated parton distribution functions and Lipatov’s effective theory for processes in multi-Regge kinematics. We predict cross sections for pair \(\psi [1S] + \psi [1S,2S]\) production by considering processes of single and double parton scattering and using the set of model parameters fixed earlier in the description of pair \(1S\)-charmonia states production at the LHC energies. Numerical calculations at the parton level were conducted using Monte Carlo event generator KaTie. Results of calculations are compared with recent LHCb Collaboration data at \(\sqrt s = 13\) TeV.