Positronium laser cooling in a magnetic field

We study realistic 3D laser cooling of positronium (Ps) in the presence a magnetic field. Triplet and singlet states mixing due to field, dynamical Stark effect, generally produce higher annihilation rates than zero-field case. is efficient only at very low field $B\ensuremath{\lesssim}50\phantom{\rule{0.16em}{0ex}}\mathrm{mT}$ high values $B⪆0.7\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. Near $100\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$ long pulses, spectrally broad enough cover most Ps Doppler profile with energy $\mathrm{mJ}$ range, are required cool Ps. Simulations based on full diagonalization Zeeman Hamiltonian kinetic Monte Carlo algorithm exactly solving rate equations indicate that an (typically from $300\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ down below $50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$) possible even also propose moving molasses can well-defined monochromatic beam useful for applications.