Particle physics

1. A proton turns into a neutron, emitting a positron and an electron neutrino.
3. The difference between the mass of a nucleus and the sum of the masses of its individual nucleons.
6. Responsible for radioactive decay (beta decay) and quark flavour changes.
7. A stable baryon composed of two up quarks and one down quark (uud).
8. The fundamental force that holds quarks together within hadrons, and nucleons together within the nucleus. It is short-range.
11. A stable baryon composed of two up quarks and one down quark (udd).
12. Fundamental particles that experience the strong interaction and make up hadrons. They have fractional charge.
14. Particles with the same mass and rest energy as their matter counterparts, but opposite charge, baryon number, and lepton number (e.g., positron, antiproton).
16. A particle and its antiparticle collide and convert their mass into energy, producing two photons to conserve momentum.

2. Acts between charged particles.
4. A neutron turns into a proton, emitting an electron and an electron antineutrino.
5. Fundamental particles that do not experience the strong nuclear force (e.g., electrons, neutrinos, muons).
9. Atoms with the same proton number but different neutron numbers.
10. Hadrons made of three quarks (e.g., protons, neutrons).
13. The rate of decay of a sample (number of nuclei decaying per second). Unit: Becquerel.
15. The energy required to separate a nucleus into its constituent protons and neutrons.
17. Composite particles that experience the strong nuclear force. They are split into baryons and mesons.