However, one form of the uncertainty principle is:
This means that the uncertainty in the energy of a particle multiplied by the uncertainty of time is greater than or equal to a constant. So for a very very short time the uncertainty in the energy can be large.
However if you look at the initial decaying particle and the final decay products, one observes that energy is conserved. The virtual particles exist for such a short time that they can never be observed.
Most processes among fundamental particles are mediated by virtual carrier particles. For example see neutron beta decay, the production of charm particles, or the decay of an eta-c particle.
Question: If an electron and a positron collide to produce a Z, is the Z a virtual particle?
