- #1
71GA
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Homework Statement
Two protons with kinetic energies ##W_{k1}=4GeV## and ##W_{k2}=2GeV## colide and form new particles. What is the mass of newly born particles?
Homework Equations
\begin{align}
W_{before}&=W_{after}\\
p_{before}&=p_{after}\\
W^2 &= {W_0}^2 + p^2c^2 \longleftarrow \substack{\text{Lorentz invariant}}
\end{align}
The Attempt at a Solution
First i wrote the energy conservation law:
\begin{align}
W_{before} &= W_{after}\\
W_{k1} + W_{k2} + 2W_{0p} &= \sqrt{{W_{0~after}}^2 +p^2c^2}\longleftarrow\substack{\text{Here the $W_{0~after}$ is a full}\\\text{rest energy after colision}}\\
W_{k1} + W_{k2} + 2W_{0p} &= \sqrt{\underbrace{\left( 2W_{0p} + W_{0m} \right)^2}_{\smash{\substack{\text{after collision we have}\\\text{2 $p^+$ and new mass $m$}}}} +p^2c^2}
\end{align}
Here i am not sure what to do with the ##p^2c^2##. Can i just take the mass frame and say ##p=0##? Why yes and why not?
Other option i am thinking of is to say that ##pc = \sqrt{{W_{k~before}}^2 - 2W_{k~before}W_{0~before}}##. Here i know that ##W_{0~before}=2W_{0p}##, but i am not sure what to put in for ##W_{k~before}##. Can i do it like ##W_{k~before} = W_{k1}+W_{k2}##?
Which of these two options is right/wrong and why? If both are wrong please tell me how to fix them to become ok.