I have read these questions:
where dmckee specifically mentions J/Ψ meson production as a clear example when a pair of virtual particles is knocked on shell from the nucleon see.
and where annav says "With the above background it is evident that virtual particles turn into real when they acquire mass and keep their quantum numbers: The photon hitting an electron and exchanging a virtual electron with the field of some atom (through a virtual photon or Z) creates a pair by the electron becoming real."
where Solenodun Paradoxus says " But it is only an analogy, and it has its limitations. Most of the newbie questions about virtual particles can and should be addressed in the full mathematical framework which is interacting Quantum Field Theory. Any kind of explanation involving virtual particles is just hand-waving."
and Arnold Neumaier says "Virtual particles have no dynamics. The latter is always tied to a state, which - unlike virtual particles - necessarily respects causality. Hence they cannot ''become'' anything."
And I got curious, but confused. Some answers say:
it is not possible,
some answers say it is possible (J/Ψ meson production),
some say it is only possible as far as we say that virtual particles mediate forces between real particles, so they have real effects.
I would like to settle this for good.
Which one is it really:
Virtual particles can be knocked on shell and become real
Virtual particles can never become real
Virtual particles have real effects on real particles