Timeline for Does positron-electron annihilation preserve enough info to reverse exactly
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4 events
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| Nov 25, 2014 at 19:56 | comment | added | Cheers and hth. - Alf | @Sofia: Thank you. The "standard model" I referred to is the Standard Model of particle physics, the prevalent theory (or theories) since the mid 1970's. Re conservation of momentum, I understand what that means for ordinary momentum, where in the rest frame of collision it's zero and allows any directions. But I don't understand your comment about angular momentum. As I understand it we're talking about at least or exactly two photons, since conservation of ordinary momentum in the rest frame of collision requires that. Is that wrong? | |
| Nov 25, 2014 at 14:45 | comment | added | Sofia | @Cheers and hth: I don't know the standard model that you mention, but I can say that gamma rays are very energetic. So, I suppose the gamma photon can be described with a definite linear momentum. The laws of conservation (including total spin projection if the photon is polarized, because the photon has angular momentum +-ħ) should define in which directions with respect to the gamma linear momentum, are emitted the e^- and the e^+. So, it's not the photon that has memory, but the conservation laws. The only thing I am not sure, which conservation law is not symmetrical in e^- vs. e^+. | |
| Nov 25, 2014 at 3:19 | comment | added | Cheers and hth. - Alf | Thanks! I'm still wondering, are the gamma rays emitted in any particular direction relative to the original particle pair? And -- does this follow from the rules of the standard model, or is it plain observed facts not accounted for by the model? | |
| Nov 24, 2014 at 18:25 | history | answered | mrf1g12 | CC BY-SA 3.0 |