BRAINCAKEConservation of Charge, Baryon Number and Lepton Number
In every particle interaction and decay, three quantities are always conserved: charge Q, baryon number B and lepton number L. The total of each before must equal the total after. If any one is not conserved, the reaction cannot happen.
Values to learn:
• quarks B = +1/3, antiquarks B = −1/3
• baryons (p, n) B = +1, antibaryons B = −1, mesons B = 0
• leptons (e−, νe) L = +1; antileptons (e+, νe) L = −1
• hadrons have L = 0; leptons have B = 0
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Key terms in this lesson
- baryon
- A hadron made of three quarks, such as the proton or neutron.
- meson
- A hadron made of one quark and one antiquark.
- lepton
- A fundamental particle, such as the electron or neutrino, that does not feel the strong nuclear force.
- quark
- A fundamental particle that combines with others, bound by the strong nuclear force, to form hadrons such as protons and neutrons.
More in Fundamental Particles
- Hadrons and Leptons
- The Strong Nuclear Force
- Quarks and Antiquarks
- Quark Composition of Protons and Neutrons
- Baryons and Mesons
- Beta-Minus Decay and Quarks
- Beta-Plus Decay and Quarks
- The Weak Interaction
All 11 lessons in Fundamental Particles · All OCR A-level Physics topics