Editing Invariant mass (section)

=== Collider experiments ===
In particle collider experiments, one often defines the angular position of a particle in terms of an azimuthal angle&nbsp;<math> \phi </math> and [[pseudorapidity]] <math> \eta </math>. Additionally the transverse momentum, <math> p_{T} </math>, is usually measured. In this case if the particles are massless, or highly relativistic (<math> E \gg m </math>) then the invariant mass becomes:
<math display="block">M^2 = 2 p_{T 1} p_{T 2} ( \cosh(\eta_1 - \eta_2) - \cos (\phi_1 - \phi_2) ) .</math>