The main problem was angular momentum distribution between the Sun and planets.

Because the positron can be polarized, also the momentum distribution for the two spin states in magnetized materials can be obtained.

This interested Maxwell, who in 1859 derived the momentum distribution later named after him.

Compton spectroscopy for the investigation of momentum distribution of the valence electron shells.

He also took up the study of positron annihilation in solids, which became a new tool for measuring the momentum distribution of bound electrons.

For a momentum distribution , the fraction of particles with magnitude of momentum between and is:

In contrast, a momentum (rather than position) measurement of a free particle can be QND because the momentum distribution is preserved by the particle's self-Hamiltonian p/2m.

The inelastic collisions will cool the neutrons and the elastic will rearrange the momentum distributions.

Note the momentum distribution obtained by integrating over all x is constant.

If one chooses the origin at the beam axis and the beam is cylindrically symmetric (at least in its momentum distribution), the external angular momentum will vanish.