How is beta decay described in terms of quarks?
A neutron can decay into a proton, an electron and an antineutrino. A neutron consists of an ‘up’ quark and two ‘down’ quarks. A proton consists of two ‘up’ quarks and one ‘down’ quark. The electron and the antineutrino are both leptons. How is it that one of the quarks appears to have changed from a ‘down’ quark to an ‘up’ quark? A neutron consists of “up” and “down” quarks: n = (udd). Similarly, a proton is p = (uud) The electric charge of the u quark is 2/3 (in units of the elementary charge) and the electric charge of the d quark is -1/3. As a result the proton has charge 1 and the neutron is neutral. The neutron decay goes via the following mechanism: The d quark decays into u quark and a virtual W- boson. As a result of the decay, the neutron is converted to proton. The virtual W- boson lives for 10-26 seconds and than decays to electron and antineutrino. Blink and you miss it! Return to top of page and menu Medical Physics Scanning: what are the features and advantages of MRI, P
