Answer:
Quarks
Explanation:
In the standard models, fundamental particles that are the constituents of matter are divided into two groups:
- Leptons: these are particles that do not feel the strong nuclear interaction. Leptons include: electron, muon, tau particle, and the three neutrinos.
- Quarks: these are the particles that interacts via the strong nuclear force. There are six quark flavours: up, down, charme, strange, top, bottom.
Quarks do not appear in nature as individual particles, but always inside more composite particles, namely:
- Mesons: these particles consist of a pair of quark and antiquark.
- Baryons: these particles are made of 3 quarks or 3 antiquarks.
Protons and neutrons are also baryons. In particular:
- A proton consists of 2 quarks up and 1 quark down
- A neutron consists of 2 quarks down and 1 quark up
