Question

In a collision, how do I label the particles to calculate the Mandelstam variables $u$ and $t$?

Answer 1

HEY SAKNA HERE

It can be either, provided you adopt a definition, state it and stick to it. In a typical experiment, in the lab frame there is a beam particle, a target particle, a scattered particle and a recoil particle: t t is taken from the difference between the beam particle and the scattered particle and it will be clear whether 3 or 4 is the 'scattered' particle either from the experimental apparatus (3 might be detected at small angles in a hodoscope some distance away, 4 might be a slow particle emerging from the target at large angles) or from the particles (for π − p→π + Δ −  π−p→π+Δ− the π +  π+ is clearly scattered and the Δ Δ is the recoil). With your particles (and without further details of the detector) it's ambigious and not clear so you can make your own decision.

HOPE IT HELP

PLZ MARK AS BRAINLIEST

Answer 2

Explanation:

Solution. The Mandelstam variables are defi ned, for a process 1 + 2 → 3 + 4, as ... We can calculate it for the case of identical particles like so: ... Relevant elastic collision for the t and u Mandelstam variables.