A hadron and a QCD (Quantum Chromodynamics) particle are related but distinct concepts in particle physics.
Hadron: A hadron is a type of particle that experiences the strong nuclear force, which is mediated by gluons. It consists of quarks and/or antiquarks bound together by the strong force. There are two main categories of hadrons: baryons and mesons.
Baryons: Baryons are hadrons composed of three quarks. Protons and neutrons are examples of baryons. Protons are made up of two up quarks and one down quark, while neutrons consist of two down quarks and one up quark.
Mesons: Mesons are hadrons composed of a quark-antiquark pair. They consist of one quark and one antiquark. Pions are examples of mesons.
QCD Particle: QCD particles refer to particles that are governed by Quantum Chromodynamics, which is the theory that describes the strong interaction between quarks and gluons. QCD is a fundamental theory of particle physics that explains the behavior of quarks and gluons within hadrons. Quarks and gluons are the building blocks of QCD particles and interact through the exchange of gluons.
So, in summary, a hadron is a particle that experiences the strong nuclear force and can be composed of quarks and/or antiquarks, while QCD particle refers to particles governed by Quantum Chromodynamics, including both hadrons and the fundamental particles (quarks and gluons) that compose them.