J/psi production at sqrt(s)=1.96 and 7 TeV: Color-Singlet Model, NNLO* and polarisation

TL;DR

This paper evaluates J/psi production in proton-proton collisions at 1.96 and 7 TeV using the Colour-Singlet Model with NLO and NNLO* corrections, showing compatibility with experimental polarisation data.

Contribution

It demonstrates that the Colour-Singlet Model, including higher-order corrections, can accurately describe J/psi production and polarisation data, challenging previous claims of inconsistency.

Findings

CSM reproduces existing data with NNLO* corrections.

J/psi polarisation becomes more longitudinal at higher P_T.

Prompt J/psi polarisation aligns with experimental observations when combining direct and chi(c) contributions.

Abstract

We study J/psi production in pp collisions at sqrt(s)=1.96 and 7 TeV using the Colour-Singlet Model (CSM), including next-to-leading order (NLO) corrections and dominant alphaS^5 contributions (NNLO*). We find that the CSM reproduces the existing data if the upper range of the NNLO* is near the actual --but presently unknown-- NNLO. The direct yield polarisation for the NLO and NNLO* is increasingly longitudinal in the helicity frame when P_T gets larger. Contrary to what is sometimes claimed in the literature, the prompt J/psi yield polarisation in the CSM is compatible with the experimental data from the CDF collaboration, when one combines the direct yield with a data-driven range for the polarisation of J/psi from chi(c).