Towards Quarkonium Fragmentation from NRQCD in a Variable-Flavor Number Scheme

TL;DR

This paper develops a framework for quarkonium production at high transverse momentum using NRQCD at NLO, incorporating variable-flavor number scheme fragmentation functions with uncertainty quantification.

Contribution

It introduces a novel approach combining NRQCD NLO calculations with VFNS fragmentation functions and a Monte Carlo method for uncertainty estimation.

Findings

Preliminary VFNS fragmentation functions constructed with proper threshold evolution.

Uncertainty quantification achieved via Monte Carlo replica approach.

Framework applicable to high transverse momentum quarkonium production.

Abstract

We address quarkonium formation at moderate to large transverse momenta, where the single-parton collinear fragmentation prevails over the short-distance emission, directly from the hard sub-scattering, of the constituent heavy-quark pair. We rely on Non-Relativistic-QCD (NRQCD) Next-to-Leading Order (NLO) calculations for all parton fragmentation channels to quarkonia, taken as proxies for initial-scale inputs. Preliminary sets of Variable-Flavor Number-Scheme (VFNS) fragmentation functions (FFs) are built via a DGLAP scheme that properly accounts for evolution thresholds. Statistical errors are assessed via a Monte Carlo (MC), replica-like approach aimed at catching Missing Higher-Order Uncertainties (MHOUs).