# special relativity questionWatch

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#1
Im trying to use the Lorentz transformation but I am having trouble identifying which reference frame is which.
Say if a particle decays into two others, is the rest frame of the particle S and the lab frame S' or vice versa?

And if the question says 'a particle is produced with a momentum of 250Gev/c along the x direction of the lab frame', is this the momentum in the lab frame or the rest frame? and can you assume the momentum in the rest frame is also along the x direction? (there is only 1 particle here, its not decaying into two, sorry if my wording is still dodgy)
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1 year ago
#2
(Original post by IDontKnowReally)
Im trying to use the Lorentz transformation but I am having trouble identifying which reference frame is which.
Say if a particle decays into two others, is the rest frame of the particle S and the lab frame S' or vice versa? ....
It depends on what other info that you are given - like is the particle travelling at some speed with respect to a stationary frame of reference and the two decay products are travelling at what speed with respect to which frame of reference.
To my remembrance, the frame of reference are usually stated in the context of the problem.

(Original post by IDontKnowReally)
.....
And if the question says 'a particle is produced with a momentum of 250Gev/c along the x direction of the lab frame', is this the momentum in the lab frame or the rest frame? and can you assume the momentum in the rest frame is also along the x direction? (there is only 1 particle here, its not decaying into two, sorry if my wording is still dodgy)
The momentum is with respect to the lab frame, so the lab frame is taken as stationary. But you take the particle's frame as rest frame, so the lab is moving but you need to extract the speed from the 250 GeV/c.
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