Question

Which of the following is not made by quarks?
A. Neutron
B. Positron
C. Proton
D. $\pi -$ meson

Answer 1

Recall the table of elementary particles and hence the hadrons, baryons and leptons. There are six types of quarks in total: up, down, strange, top, bottom, charm. Any of the two or three quarks make up the most of the elementary particles.

Complete answer:
As we know the quark is an elementary particle and it is a fundamental constituent of matter. All the particles found in the universe are made up of either quarks or leptons. They do not exist independently but as a constituent part of the matter. There are six types of quarks in total: up, down, strange, top, bottom, charm. Now, let us see how the particles mentioned in the options are formed.

Neutron: As we know, the neutron is classified as a hadron since it is made up of three valence quarks. It is made up of two down quarks and one up quark. Thus, the neutron is made up of quarks.
Proton: As we know, the proton is classified as a hadron since it is made up of three valence quarks. It is made up of two up quarks and one down quark.
$\pi -$meson: $\pi -$ meson has zero spin and is composed of first generation quarks. It is also made up of one up quark and one anti-up quark or down quark and anti-down quark.
Positron: We know that the positron is an anti-electron that is the antiparticle of an electron. Since the electron is an elementary particle it cannot be made up of quarks. Thus, the positron is not made up of quarks.

So, the correct answer is option B.

Note: The particles made by quarks are also elementary particles or fundamental particles. There are a total 12 elementary particles which include 6 quarks, 3 electrons, and 3 neutrinos. Students can remember which particles are made by quarks by remembering the fact that the nucleus of an atom is made up of quarks. That is proton and neutron.