Did this video help you?
Hadrons (AQA AS Physics)
Revision Note
Baryons & Mesons
Hadrons
- Hadrons are the group of subatomic particles that are made up of quarks
- Therefore, hadrons can feel the strong nuclear force
- There are two classes of hadrons:
- Baryons (3 quarks)
- Mesons (quark and anti–quark pair)
- The most common baryons are protons and neutrons
- The most common mesons are pions and kaons
Hadrons may be either a baryon or a meson
Anti–hadrons
- There are two classes of anti–hadrons:
- Anti–baryons (3 anti-quarks)
- Anti–mesons (quark and anti–quark pair)
Anti-hadrons may be either an anti-baryon or an anti-meson
- Quarks have never been discovered on their own, always in pairs or groups of three
- Note that all baryons or mesons have integer (whole number) charges eg. +1e, -2e etc.
- This means quarks in a baryon are either all quarks or all anti–quarks. Combination of quarks and anti–quarks don’t exist in a baryon
- e.g.
- The anti–particle of a meson is still a quark and anti–quark pair. The difference being the quark becomes the anti–quark and vice versa
Worked example
The baryon Δ++ was discovered in a particle accelerator using accelerated positive pions on hydrogen targets.Which of the following is the quark combination of this particle?
Examiner Tip
- Remembering quark combinations is useful for the exam
- However, as long as you can remember the charges for each quark, it is easy to figure out the combination by making sure the combination of quarks adds up to the total charge of the particle (just like in the worked example!)
You've read 0 of your 5 free revision notes this week
Sign up now. It’s free!
Did this page help you?