# How often does photons morph into matter and antimatter?

We know that matter-antimatter collisions are reducing the two into pure energy or photons. Similarly the reverse is possible where a photon can spontaneously morph into two equal particles of matter and antimatter.

Ignoring the fact that the antimatter would be short-lived and be annihilated by matter again,

• is there any theory or evidence on how often the spontaneous process of creating matter/antimatter from a photon takes place naturally?
• I recommend reading QED: The strange theory of light and matter by Richard Feynman! He explains how such fundamental interactions take place (he focuses more on the interaction of charges but the principles are similar) – Jaywalker Jan 12 '16 at 7:04
• Photons are no more "pure energy" than any other states of the vacuum. Matter and energy are two sides of the same thing and should be treated the same way. Pair production cross sections can be calculated very precisely with quantum electro dynamics, but the math takes some practice. Jaywalker beat me to the best book recommendation I could give for getting a feeling for the basic idea behind the theory without the math. – CuriousOne Jan 12 '16 at 7:16

Similarly the reverse is possible where a photon can spontaneously morph into two equal particles of matter and antimatter.

Wrong, a photon has to interact with some other particle or field in order, if it has enough energy , to create a particle antiparticle pair.

This is because of special relativity: the photon has a mass zero whereas the particle antiparticle pair will have at least twice the mass of the particle , i.e. the dot product of the two generated four vectors should have that mass. Momentum conservation would be violated, since in their center of mass the pair would have momentum zero , all the energy would go to the pair masses and opposite to each other momenta adding to zero, whereas the photon carries momentum h/lamda in all frames .

The probability of a gamma generating a pair of particle antiparticle can be calculated using the appropriate to the target fields Feynman diagrams. For example, the left diagram of scattering off the field of an atom Z: pair production by a gamma ray (left) or an electron (right).

There is a prescription that turns a Feynman diagram into an integral, and the evaluation of the integral will give the probability of this reaction happening (how often in your title)