Theory-based approach allows access to small lateral motions of quarks within protons

Nuclear theorists at Brookhaven National Laboratory and Argonne National Laboratory worked to calculate the Collins-Soper kernel, a quantity that describes how the distribution of transverse momentum of quarks inside a proton changes with collision energy. successfully adopted a new theoretical approach.

The study is published in the journal Physical Review D.

The new calculations exactly match model-based reconstructions from particle impact data. This is particularly effective for quarks with small transverse momentum, where previous methods were insufficient.

This theory-based approach provides the first accurate calculation of how the distribution of quark transverse momentum within a proton varies with collision energy. This approach provides much more accurate theoretical predictions about the small transverse motions of quarks inside protons. This eliminates the need to model quark-gluon interactions, which are dominated by the most complex strong forces.

The researchers used lattice quantum chromodynamics (QCD), a supercomputer-based simulation that tracks the interactions of quarks and gluons on a 4D space-time lattice. The new theoretical approach allowed the team to greatly simplify lattice QCD calculations and obtain accurate results even for small transverse motions of quarks, where quark-gluon interactions are strong and complex.

Such an accurate description of the small transverse motions of quarks could not be achieved in previous lattice QCD calculations using more conventional approaches.

The new results for low transverse momentum quarks are consistent with previous results, but are more precise and have much smaller uncertainties. These are also consistent with models developed to explain existing experimental data.

These results demonstrate that new approaches can be used to predict and interpret future experimental results at different collision energies at the future EIC collider and the European Large Hadron Collider under construction at Brookhaven National Laboratory. It shows.

Physicists will use these predictions and experiments to learn about the tiny transverse motions of quarks within protons and how that motion contributes to the proton’s spin.