A certain particle has uds quarks (one up one down and one strange quark). (a) Is the particle a lepton or a hadron? Explain. (b) Is the particle a boson or a fermion? Explain. (c) What is the charge of this particle? (d) What is the strangeness number of this particle?
The correct answer and explanation is:
Correct Answers:
(a) The particle is a hadron.
(b) The particle is a fermion.
(c) The charge of the particle is 0.
(d) The strangeness number of the particle is −1.
Explanation:
(a) A particle composed of quarks is classified as a hadron, not a lepton. Leptons include particles such as electrons, muons, and neutrinos, which are elementary and do not have internal quark structure. Since this particle has three quarks (up, down, and strange), it falls into the category of hadrons. Specifically, it is a baryon, which is a type of hadron composed of three quarks. Baryons include particles like protons and neutrons.
(b) The particle is a fermion because it is made of three quarks. Fermions are particles with half-integer spin, such as 1/2, 3/2, etc. Since each quark has a spin of 1/2, the combination of three quarks results in an overall half-integer spin, which is characteristic of fermions. This is in contrast to bosons, which have integer spins (0, 1, 2, etc.) and often act as force carriers.
(c) To determine the charge of the particle, add the charges of its constituent quarks:
- Up quark (u): +2/3
- Down quark (d): −1/3
- Strange quark (s): −1/3
Total charge = (+2/3) + (−1/3) + (−1/3) = 0.
Thus, the particle is electrically neutral.
(d) The strangeness number is associated with the number of strange quarks in a particle. Each strange quark contributes −1 to the strangeness number. Since this particle contains one strange quark, its strangeness number is −1. Strangeness is a quantum number conserved in strong interactions but not in weak interactions, and it helps classify particles that contain strange quarks.
Therefore, the particle is a neutral, strange baryon with properties characteristic of a fermion.