Where m is the mass of an electron = mass of a positron. The particles have masses and the masses satisfy an equation like the following (forgive me, it's been 20 years so I could easily have a sign wrong):Į_1^2 = (Px^2 + Py^2 + Pz^2)c^2 - m^2c^4 (And in fact, you could if these were virtual particles that you will learn about much later in your career.) But that's not all there is to it. Now if that were all there is to it, then sure, you could do the deed. Second electron 4-vector (to get energy and momentum to add up): Here is the calculation, assume the photon travels in the +z direction: Maybe one of these will help you remember it, if not, make up your own. Yet another way of saying this is that if you want to get the best rocket ship drive, use photons because they have the highest possible ratio of momentum to energy. Another way of saying the same thing is that the photon always has too much momentum for the electron and positron to conserve momentum (assuming that the energies balance). But then it wouldn't really be a single gamma ray turning into an electron and a positron, it would have something else involved.Ī single gamma can't go to an e and p because it can never have enough energy to pay for the masses of the electron and proton (after balancing conservation of momentum). I think that Kvantti meant his comment is in the context of a bubble chamber where there is stuff available to carry off the excess energy. The only conservation law I can think of is the conservation of lepton # which appears to be preserved by virtue of the e-p pair. Your answer contradicts an earlier reply, who is right?Īlso, I don't see why a single gamma ->e-p violates any law of conservation. String theory also conserves E and p, if little else. Pair production usually occurs in the electric field of a nearby nucleus.Ĥ. It does occur vitually, but at such a high energy that just a single e-p (I'll use p for positron.)Ģ.
Is the process of pair-production, where an electron and positron are created, due to 2 colliding gamma rays annihilating eachother? Furthermore, can a single gamma ray, of sufficient energy, spontaneously annihilate itself to create the same electron and positron pair? Thirdly, is there any basis in experiment or theory that allows for a single gamma ray to interact with the quantum field in a manner than could create an electron/ poistron pair? And finally, is there a version of string theory that would allow for a single gamma ray to interact with tiny dimesions whereupon an electron/ positron pair could be created?ġ. We know an electron colliding into a positron annihilate one another and 2 recoiling gamma rays are produced moving in opposite directions.
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