Question

(a) Is a hadron always a baryon?

(b) Is a baryon always a hadron?

(c) Can an unstable baryon decay into a meson, leaving no other baryon?

Short answer

(a) No, a hadron is not always a baryon.

(b) Yes, a baryon is always a hadron.

(c) No, an unstable baryon cannot decay into a meson, leaving no other baryon.

Step-by-step solution

Meson, Baryon, Hadrons

Mesons are hadronic subatomic particles made up of an equal number of quarks and antiquarks, generally one of each, and linked together by strong interactions in particle physics.

A baryon is a form of composite subatomic particle in particle physics that has an odd number of valence quarks.

A hadron is a composite subatomic particle made up of two or more quarks bound together by the strong interaction in particle physics.

Is hadron a baryon

(a)

Hadrons are particles composed of quarks held together by strong force. They can consist of 3 quarks - such particles are called baryons, 2 quarks - mesons, or possible exotic hadrons composed of $\ge 4$ quarks.

Therefore, hadron is not always a baryon.

Is baryon a hadron

(b)

Baryons are composed of 3 quarks held together by a strong force, so they are a

subcategory of the hadron family of particles.

Therefore, baryon is always a hadron.

Decay of baryon

(c)

Decaying of an unstable baryon into a meson and leaving no other baryon would violate conservation of baryon number. Baryons carry a baryon number B = 1, while mesons have baryon number B = 0. As baryon number is conserved in baryon decay, an unstable baryon cannot decay into a meson, without leaving a baryon.

Therefore, no an unstable baryon cannot decay into a meson.