Charmonia production in hadron colliders and the extraction of colour-octet matrix elements

We present the results of our analysis on charmonia (J/ψ and ψ′) hadroproduction taking into account higher-order QCD effects induced by initial-state radiation in a Monte Carlo framework, with the colour-octet mechanism implemented in the event generation. We find that those colour-octet matrix elements extracted so far from Fermilab Tevatron data for both J/ψ and ψ′ production have to be lowered significantly. We finally make predictions for charmonia production at the LHC, presenting a code for a fast simulation with PYTHIA based on the colour-octet model