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Abstract

The process of turning a proton into a neutron, positron and
electron-neutrino in a strong plane-wave electromagnetic field, is studied.
This process is forbidden in vacuum and is seen to feature an exponential
suppression factor which is non-perturbative in the field amplitude. The
suppression is alleviated when the proton experiences a field strength of about
13 times the Schwinger critical field in its rest frame. Around this threshold
the lifetime of the proton, in its rest frame, is comparable to the usual
neutron decay lifetime. As the field strength is increased, the proton lifetime
becomes increasingly short. We investigate possible scenarios where this
process may be observed in the laboratory using an ultra-intense laser and a
high-energy proton beam with the conclusion, however, that it would be very
challenging to observe this effect in the near future.