  In this research paper, we investigate the decay of the proton into neutron,
positron and electron neutrino in the presence of an external electromagnetic
field with circular polarization. Different physical quantities related to this
decay process, such as proton's decay rate and its lifetime, are calculated
based on the S-matrix approach. The proton and positron are treated as
Dirac-Volkov states, while the neutron and electron neutrino are free-states.
We have found that, though it can not occur in vacuum, the proton's decay
process into neutron, positron and electron neutrino becomes possible in the
presence of laser field with high intensities near or close to the Schwinger
limit. In addition, near this limit and for some frequencies, the proton's
lifetime can be comparable to that of the neutron, and the required laser
strength, from which this decay becomes possible, depends on the chosen laser
source.
