Spin-Exchange in Hydrogen-Antihydrogen Collisions

TL;DR

This paper investigates spin-exchange processes in ultracold hydrogen-antihydrogen collisions, revealing the dominant role of the strong force and how CPT violation could significantly alter collision cross-sections.

Contribution

It introduces a model linking spin-exchange cross sections to strong force scattering lengths and highlights the impact of CPT violation on collision behavior.

Findings

Spin-exchange driven mainly by strong force between proton and antiproton.

Cross sections proportional to difference in strong force scattering lengths.

CPT violation causes significant changes in energy dependence of cross sections.

Abstract

We consider the spin-exchange in ultracold collisions of hydrogen ($H$) and antihydrogen ($\bar{H}$) atoms. The cross sections for transitions between various hyperfine states are calculated. We show that the process of spin exchange in $\bar{H}-H$ collisions is basically driven by the strong force between proton and antiproton, that spin-exchange cross-sections are proportional to the difference of singlet and triplet strong force S-wave scattering lengths, while the strong force effects are enhanced about $10^9$ times due to long range atomic forces. We show that any difference in hyperfine structure of $H$ and $\bar{H}$ (CPT violation) manifests itself in radical change of spin-exchange cross-sections energy behavior.