Automated calculation of Jet fragmentation at NLO in QCD

TL;DR

FMNLO is a new NLO QCD framework that combines Monte Carlo generators and fragmentation functions, enabling fast, accurate predictions for jet fragmentation at the LHC and supporting future FF fits.

Contribution

This work introduces FMNLO, a hybrid phase-space slicing and subtraction scheme framework, interfaced with MG5 aMC@NLO, for efficient NLO calculations of jet fragmentation processes.

Findings

FMNLO provides accurate NLO predictions for fragmentation measurements at the LHC.

The framework allows rapid calculations for various fragmentation functions using interpolation.

A NLO fit reveals significant differences in gluon fragmentation functions compared to existing models.

Abstract

We present FMNLO, a framework to combine general-purpose Monte Carlo generators and fragmentation functions (FFs). It is based on a hybrid scheme of phase-space slicing method and local subtraction method, and accurate to next-to-leading order (NLO) in QCD. The new framework has been interfaced to MG5 aMC@NLO and made publicly available in this work. We demonstrate its unique ability by giving theoretical predictions of various fragmentation measurements at the LHC, followed by comparison with the data. With the help of interpolation techniques, FMNLO allows for fast calculation of fragmentation processes for a large number of different FFs, which makes it a promising tool for future fits of FFs. As an example, we perform a NLO fit of parton fragmentation functions to unidentified charged hadrons using measurements at the LHC. We find the ATLAS data from inclusive dijet production show a strong constraining power. Notable disparities are found between our gluon FF and that of BKK, DSS and NNFF, indicating the necessities of additional constraints and data for gluon fragmentation function.