Weak interaction
In a strange quantum effect, this transformation releases a particle called a W boson. This is the gauge boson (force-carrying particle) of weak force. Oddly, the W boson has a mass about 80 times as much as a neutron. This sort of thing actually happens very often in quantum mechanics, but it follows the conservation of energy because it happens so quickly. After 3x10–25 seconds, the W boson breaks into an electron and an electron antineutrino. (The electron antineutrino doesn't really do much). This releases the electron and basically creates a proton from a neutron.