Modelling of Antihelium-3 Cosmic-Ray Propagation

The yet undetected dark-matter particles are a candidate to account for the missing mass in the Universe. Arguably, the dark-matter composition is one of the most fascinating topics beyond the Standard Model of particle physics. One of the indirect dark-matter searches is based on antinuclei cosmic-ray measurements. The $^{3}\overline{\rm He}$ cosmic rays are expected to be a golden channel for such searches. However, precise modelling of cosmic rays in the galaxy and in the solar system is needed. The full-scale description of the $^{3}\overline{\rm He}$ cosmic rays in the galaxy requires three main components: the production cross section, the annihilation cross section and the propagation. The cosmic-ray transport equation involving these components can be solved either by some simplified analytical approaches or by using numerical solvers which include an as precise as possible description of the galaxy. One of such publicly available numerical solvers is the GALPROP code. In this note, the required updates to include the $^{3}\overline{\rm He}$ cosmic rays in GALPROP are discussed. For the source functions of $^{3}\overline{\rm He}$ production, in the following two processes are described: cosmic-ray collisions with the interstellar medium and dark-matter annihilation.