- #1
metastable
- 514
- 53
If I fire an electron and positron bunch both in the same direction away from my experimental accelerator rest frame such that the electron bunch is fired with higher energy towards a "read end" collision with an already fired positron bunch and they collide a short distance away from the accelerator inside a chamber of full of detectors completely surrounding the collision. Before the collision both bunches have substantially similar momentum vector away from the accelerator. After the collision I expect the energies of the detected photons to add up to the rest energies of the annihilated particles plus the additional kinetic energy of the electron and positron bunches moving relative to the detector. But when I look at the momentum vectors of the some of the photons, they appear to have changed up to 180 degrees from the original momentum vectors of the electron-positron bunches (ie I expect some of the detected radiation to be heading in the momentum vector back towards the accelerator). The part I don't understand is where did the energy come from to change the momentum vectors of the radiation back towards the accelerator? Why does it consume no energy to change these vectors, such that the photons add up to the rest mass + kinetic energy (ie is there no energy allotment for changing the vector of the radiation detected heading back towards the accelerator)?