Transverse Properties of Baryons using Lattice Quantum Chromodynamics

Abstract

Utilising lattice Quantum Chromodynamics (QCD) to calculate nucleon matrix elements allows us to gain great insight into the internal structure of baryons that would be prohibitively diffcult to access in physical experiments. We can extract the electromagnetic and tensor form factors for not only the proton but also the heavier octet baryons, including the sigma ∑ and cascade ≡ baryons. By utilising the properties of SU(3) flavour breaking in a new method only recently published, we extrapolate our electromagnetic and tensor form factors to the physical point. We also investigate the transverse spin-dependent quark densities and how the choice of baryon spin and quark spin polarisation affects the distribution of quarks in a plane transverse to the baryon's momentum. Presenting the first lattice calculation extrapolated to the physical point, we compare the proton to those in the heavier octet baryons. These densities show interesting distortions that occur when the quark spin and baryon spin polarisation are both aligned or anti-aligned and shows the dominance of the baryon spin when determining the quark distribution inside the baryon. Following a similar procedure to the transverse spin density, we analyse the transverse `colour' Lorentz force acting on a struck quark in deep inelastic scattering experiments. Understanding the distribution of these forces could offer a significant conceptual advance in the understanding of the force mechanisms underlying confinement in QCD.