Quark

Key Stage 5

Meaning

Quarks are a type of fermion and are the constituent parts of hadrons.

About Quarks

Quarks are believed to be fundamental particles but they have never been observed on their own.

Quarks always exist as part of hadron including a baryon, which is a triplet of quarks or a meson which is a quark-antiquark pair.

There are 6 types of quark including:

• Up-quark - With a charge of \(+\frac{2}{3}\)e, two of which are found in proton and one of which is found in a neutron.
• Down-quark - With a charge of \(-\frac{1}{3}\)e, two of which are found in a neutron and one of which is found in a proton.
• Strange-quark - With a charge of \(-\frac{1}{3}\)e which decays quickly via the weak interaction into a down-quark.
• Top-quark - With a charge of \(+\frac{2}{3}\)e which decays quickly via the weak interaction.
• Bottom-quark - With a charge of \(-\frac{1}{3}\)e which decays quickly via the weak interaction.
• Charm-quark - With a charge of \(+\frac{2}{3}\)e which decays quickly via the weak interaction.

Conserved Quantities

Top-quarkCharm-quark

Quark	Charge/e	Strangeness	Baryon Number	Lepton Number
Up-quark	\(q=+\frac{2}{3}\)	\(S=0\)	\(b=+\frac{1}{3}\)	\(l=0\)
Down-quark	\(q=-\frac{1}{3}\)	\(S=0\)	\(b=+\frac{1}{3}\)	\(l=0\)
Strange-quark	\(q=-\frac{1}{3}\)	\(S=-1\)	\(b=+\frac{1}{3}\)	\(l=0\)
\(q=+\frac{2}{3}\)	\(S=0\)	\(b=+\frac{1}{3}\)	\(l=0\)
Bottom-quark	\(q=-\frac{1}{3}\)	\(S=0\)	\(b=+\frac{1}{3}\)	\(l=0\)
\(q=+\frac{2}{3}\)	\(S=0\)	\(b=+\frac{1}{3}\)	\(l=0\)

Antitop-quarkAnticharm-quark

Antiquark	Charge/e	Strangeness	Baryon Number	Lepton Number
Antiup-quark	\(q=-\frac{2}{3}\)	\(S=0\)	\(b=-\frac{1}{3}\)	\(l=0\)
Antidown-quark	\(q=+\frac{1}{3}\)	\(S=0\)	\(b=-\frac{1}{3}\)	\(l=0\)
Antistrange-quark	\(q=+\frac{1}{3}\)	\(S=+1\)	\(b=-\frac{1}{3}\)	\(l=0\)
\(q=-\frac{2}{3}\)	\(S=0\)	\(b=-\frac{1}{3}\)	\(l=0\)
Antibottom-quark	\(q=+\frac{1}{3}\)	\(S=0\)	\(b=-\frac{1}{3}\)	\(l=0\)
\(q=-\frac{2}{3}\)	\(S=0\)	\(b=-\frac{1}{3}\)	\(l=0\)