Baryon

Key Stage 5

A baryon is a type of hadron made of three quarks.

Baryons include:

Proton - A type of baryon with a mass of 1.67x10^-27kg and a charge of 1.60x10^-19 Coulombs, made of 2 Up-quarks and 1 Down-quark.
Neutron - A type of baryon with a mass of 1.67x10^-27kg and zero charge, made of 2 Down-quarks and 1 Up-quark.

There are many other baryons made from different groups of quarks. However, these are unstable and exist only for very short periods of time before decaying via the weak nuclear interaction into other, most stable, subatomic particles.

Baryons are affected by the:

NB: You only need to memorise the names and quark composition of the proton and the neutron. However, you should be able to determine the quark composition given the charge and strangeness of a given baryon and by remembering the properties of the up-quark, down-quark and strange-quark.

Baryons can be shown in the following diagram:

The composition of these baryons can be determined given their charge and strangeness.

Determine the composition of the Σ⁺	Determine the composition of the Ξ^-
Strangeness Σ⁺ has a strangeness of -1, therefore it contains a strange-quark. Charge \(+1 = -\frac{1}{3} + x + y\) \(+\frac{4}{3} =x + y\) Σ⁺ has a positive charge. This can be achieved with its strange-quark with a charge of \(-\frac{1}{3}\)e and two quarks with a charge of \(+\frac{2}{3}\)e (an pair of up-quarks). Since \(+1 = -\frac{1}{3} + \frac{2}{3} + \frac{2}{3}\) Therefore \(Σ^+ = s + u + u\) Sigma Baryon = suu	Strangeness Ξ^- has a strangeness of -2, therefore it contains two strange-quarks. Charge \(-1 = -\frac{1}{3} + -\frac{1}{3} + x\) Ξ^- has a negative charge. This can be achieved with its two strange-quarks with a charge of \(-\frac{1}{3}\)e each and another charge of \(-\frac{1}{3}\)e (a down-quark). Since \(-1 = -\frac{1}{3} + -\frac{1}{3} -\frac{1}{3}\) Therefore \(Ξ^- = s + s + d\) Xi Baryon = ssd