# Force carrier $W$-boson

A force between two particles can be described either as the action of a force field generated by one particle on the other, or in terms of the exchange of virtual force carrier particles between them.

These virtual force carrier particles are physically produced during these processes, like beta decay of neutron? Why are they called "virtual"? I know that $$W$$ boson was discovered in a physical "weak interaction" experiment, so it was actually produced.

• What do you mean by "actual(ly)", "virtual", "physical(ly)", etc... Have you completely researched "virtual particles"? – Cosmas Zachos Jun 8 at 15:24

• @Salmone The center-of-mass energy of that experiment was 540 GeV, which is definitely enough to create on-shell W bosons. That said, the W boson lifetime is so short ($10^{-24}$ seconds!) that it doesn't make much sense to talk about a "real" W boson in the above sense. Every W boson we produce is internal to some Feynman diagram before it reaches a detector, so we observe it by looking for the peak in its production rate around its on-shell mass. See the following review: cds.cern.ch/record/2103277/files/9789814644150_0006.pdf – probably_someone Jun 8 at 20:25