Measuring the phase of the scattering amplitude with vortex beams

TL;DR

This paper proposes using vortex beams in scattering experiments to directly measure the phase variation of the scattering amplitude with angle, offering enhanced sensitivity over traditional plane wave methods.

Contribution

It introduces a novel approach employing vortex beams to measure phase differences in scattering amplitudes, which is not possible with standard plane wave collisions.

Findings

Vortex beams enhance phase sensitivity in scattering measurements.

Interference of plane wave components in vortex beams reveals phase differences.

Potential applications in hadronic physics and resonance studies.

Abstract

We show that colliding vortex beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the plane wave scattering amplitude changes with the scattering angle. Since vortex beams are coherent superpositions of plane waves with different momenta, their scattering amplitude receives contributions from plane wave amplitudes with distinct kinematics. These contributions interfere, leading to the measurement of their phase difference. Although interference exists for any generic wave packet collision, we show that using vortex beams dramatically enhances sensitivity to the phase in comparison with non-vortex beams. Since the overall phase is inaccessible in a plane wave collision, this measurement would be of great importance for a number of topics in hadronic physics, for example, meson production in the resonance region, physics of nucleon resonances, and small angle elastic hadron scattering.