Quark composition: β– & β+ decay
- Beta decay happens via the weak interaction
- This is one of the four fundamental forces and it’s responsible for radioactive decays
Quark composition: β- decay
- Recall that β- decay is when a neutron turns into a proton emitting an electron and anti-electron neutrino
- More specifically, a neutron turns into a proton because a down quark turns into an up quark
Beta minus decay
Beta minus decay is when a down quark turns into an up quark
Quark composition: β+ decay
- Recall that β+ decay is when a proton turns into a neutron emitting an positron and an electron neutrino
- More specifically, a proton turns into a neutron because an up quark turns into a down quark
Beta plus decay
Beta minus decay is when an up quark turns into a down quark
Worked example
The equation for β– decay is
Using the quark model of beta decay, prove that the charge is conserved in this equation.
Answer:
Step 1: Recall the process of beta minus decay
- β− decay is when a down quark changes to an up quark
- This changes a neutron into a proton
Step 2: Determine the charge on the left hand side of the equation
- The quark composition of a neutron is
- Adding the quark charges gives:
- The left side of the equation has a charge of 0
Step 3: Determine the charge on the right hand side of the equation
- The quark composition of a proton is
- Adding up the quark charges gives:
- The electron has a charge of −1
- The anti-neutrino has a charge of 0
- Therefore, the right hand side of the equation has a charge of:
Step 4: Prove that the charge is conserved
- Since charge is equal on both sides, charge is conserved in the beta decay equation