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Puffer Fish
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I was reading about electron-positron annihilation. Typically it results in two photons, each with an energy of 511 keV, that go shooting out in opposite directions. But I read that in some instances three photons can result. Electrons have an intrinsic spin of ½, while photons have a spin of 1. So if the electron and positron have spins of +½ and -½, you will get two photons with spins +1 and -1. If, on the other hand, the electron and positron have the same spin orientation, say +½ and +½, then three photons will result, with spins +1, +1, and -1.
Well what I’m wondering is, is it possible for only one photon to result from an electron-positron annihilation? This outcome could still abide by the laws of spin conservation. Suppose the positron was traveling with a kinetic energy of 600 keV, and then a faster moving electron was shot from directly behind, say with a kinetic energy of 1.2 MeV, on an intercept course to annihilate with it. Because the kinetic energy of the system outweighs the rest masses of the two particles, any resulting photons from the annihilation would be directed in the forward vector.
You might also have to magnetically polarize the particles before shooting them out, to make sure they had the proper spin orientation for an odd-number multiple photon creation.
I thought about this and I am thinking what would tend to happen is you would have a cone of radiation with a specifically defined angle of emission. But as the kinetic energy was increased, the angle would become narrower and narrower until coherence effects started to predominate. Obviously at some extreme narrow angle you can’t have multiple photons streaming out from the same annihilation point, or at least that’s not statistically favorable.
Well what I’m wondering is, is it possible for only one photon to result from an electron-positron annihilation? This outcome could still abide by the laws of spin conservation. Suppose the positron was traveling with a kinetic energy of 600 keV, and then a faster moving electron was shot from directly behind, say with a kinetic energy of 1.2 MeV, on an intercept course to annihilate with it. Because the kinetic energy of the system outweighs the rest masses of the two particles, any resulting photons from the annihilation would be directed in the forward vector.
You might also have to magnetically polarize the particles before shooting them out, to make sure they had the proper spin orientation for an odd-number multiple photon creation.
I thought about this and I am thinking what would tend to happen is you would have a cone of radiation with a specifically defined angle of emission. But as the kinetic energy was increased, the angle would become narrower and narrower until coherence effects started to predominate. Obviously at some extreme narrow angle you can’t have multiple photons streaming out from the same annihilation point, or at least that’s not statistically favorable.