# Quarkonium production at the LHC: a data-driven analysis of NRQCD's predictions

## TL;DR

This paper investigates how NRQCD, a theoretical framework for quarkonium production, surprisingly aligns with LHC data showing simple, universal production patterns, and discusses how future polarization measurements could confirm or challenge this theory.

## Contribution

It provides a data-driven analysis demonstrating NRQCD's ability to explain universal quarkonium production at the LHC and predicts specific polarization signatures for future tests.

## Key findings

- NRQCD can accommodate universal production patterns through cancellations.
- Predicted strong, opposite polarizations for $ ext{chi}_{c1}$ and $ ext{chi}_{c2}$.
- Future polarization measurements could confirm or challenge NRQCD predictions.

## Abstract

While non-relativistic QCD (NRQCD) foresees a variety of elementary quarkonium production mechanisms naturally leading to state-dependent kinematic patterns, the LHC cross sections and polarization measurements reveal a remarkably simple production scenario, independent of the quantum numbers and masses of the quarkonia. Surprisingly, NRQCD is able to accommodate the observed universal scenario, through a series of conspiring cancellations smoothing out its otherwise variegated hierarchy of mechanisms. This seemingly unnatural solution implies that the $\chi_{c1}$ and $\chi_{c2}$ polarizations, not yet measured, are strong and opposite, representing the only potential exception to a remarkably simple picture of quarkonium production. The observation of a large difference between $\chi_{c2}$ and $\chi_{c1}$ polarizations, which cannot be indirectly extracted from existing measurements because they mutually cancel each other in their contribution to the observed J/$\psi$ production, would be a smoking gun signal finally proving the multifaceted but mysteriously elusive structure of NRQCD. On the other hand, the measurement of two similar, small polarizations will urge improved P-wave calculations, if not a substantial revision of the NRQCD hierarchies.