Jefferson Lab JAM
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About

The JAM (Jefferson Lab Angular Momentum) Collaboration is an enterprise involving theorists and experimentalists from the Jefferson Lab community to study the quark and gluon structure of hadrons through global QCD analysis of parton distribution functions (PDFs), fragmentation functions (FFs) and transverse momemtum dependent (TMD) distributions. The analyses are performed in the framework of collinear factorization at NLO in perturbative QCD, utilizing Monte Carlo methods and modern Bayesian analysis techniques.

Library

A collection of codes and scripts (in fortran, python, mathematica) is provided, along with interpolation tables for PDFs and FFs. The library is available at JAMLIB.

Selected Results

Pion and Kaon fragmentation from JAM16

Leading twist and twist 3 distributions from JAM15

Roadmap

Tha main gloal of the JAM analysis is to perform a universal fit to extract collinear spin-averaged and spin-dependent parton densities, as well as parton to hadron fragmentation functions from all available data. At present the observables with checkmarks has been included in the JAM analysis.

Iterative Monte Carlo method

The JAM analysis uses a novel fitting procedure based on Monte Carlo techniques to have robust estimates of expectation values and variances of the extracted distributions.