# If electrons are fundamental particles then why do they -

1. Apr 12, 2015

### invrlovduanyway

If electrons are fundamental particles and leptons then what happens when they emit or absorb photons or Z particles? What is known about the mechanism of these aborptions or emissions for any particles? Do the absorbed electrons gain mass as particles are described to do as they move nearer to the speed of light? or do the absorbed photons cause electrons to become muons or taus?

Further, if an electron is accelerated nearer the speed of light will it at some point obtain the mass of a muon or tau? Would this make that equal in character to the muon or tau? thanks

2. Apr 12, 2015

### phinds

Particles do not gain mass as they are accelerated, they gain the energy equivalent but in their own frame of reference, they have not changed mass.

Think about it this way. EVERY electron is traveling near the speed of light from some reference frame and slower in other reference frames. Can an electron have more than one mass at a time?

3. Apr 13, 2015

### Staff: Mentor

No. Photons are associated with the electromagnetic interaction, which never changes the type of particle.

In order to convert among electron, muon and tau, you have to use the weak interaction. For example, a μ- can decay into a muon neutrino and a virtual W-, with the W- producing an electron plus an electron-antineutrino, giving the net result $$\mu^- \rightarrow e^- + \nu_\mu + {\bar \nu}_e$$

4. Apr 13, 2015

### Staff: Mentor

The Quantum Field Theory picture is not like that. The theory says nothing in terms of everyday pictures of that sort.

Quantum fields are a superposition in the quantum sense of zero particles, one particle, two particles etc etc and the same field for each particle permiates all space. All it alolows you to precict is the probability of when a particle will be detected. For examople eleectrons can emit photons but the theory doesnt say how that happens, simply the probabilities of detecting an emitted photon and the electron loosing energy.

Thanks
Bill