Hi, I'm just trying to get my head around beta decay and would appreciate it if someone could correct me if I'm wrong. Beta minus decay involves the transformation of a neutron into a proton, electron and electron antineutrino. This is all mediated by the weak nuclear force and involves W and Z bosons. In the case of beta minus decay it involves a W- boson which is released when the neutron turns into a proton. The W- boson then rapidly decays into an electron and an antielectron neutrino. The mass of the products is less than the mass of the reactants which is explained by binding energy where the products (electrons and antineutrinos) have high kinetic energy which compensates for the missing mass. I just had a couple of questions: As I understand it, the neutron undergoes a quark flavor change which is why it transforms into a proton. What causes the flavor change? Is it the W- boson? Also, could someone clarify what is meant by a virtual particle? As I understand it, the term is somewhat arbitrary and refers to a particle that is very short lived, e.g. W- boson. Is the W- boson in beta minus decay a virtual particle? How do scientists prove virtual particles exist?