particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

, the term particle zoo is used colloquially to describe the relatively extensive list of known

subatomic particle In physical sciences, a subatomic particle is a particle that composes an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a pr ...

s by comparison to the variety of species in a

zoo A zoo (short for zoological garden; also called an animal park or menagerie) is a facility in which animals are kept within enclosures for public exhibition and often bred for Conservation biology, conservation purposes. The term ''zoological g ...

. In the

history of particle physics The idea that matter consists of smaller particles and that there exists a limited number of sorts of primary, smallest particles in nature has existed in natural philosophy at least since the 6th century BC. Such ideas gained physical credibilit ...

, the topic of particles was considered to be particularly confusing in the late 1960s. Before the discovery of quarks, hundreds of strongly interacting particles (

hadron In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the ele ...

s) were known and believed to be distinct

elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions ( quarks, leptons, an ...

s. It was later discovered that they were not elementary particles, but rather composites of

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...

s. The set of particles believed today to be elementary is known as the

Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...

and includes

s, bosons and

lepton In particle physics, a lepton is an elementary particle of half-integer spin ( spin ) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons or muons), and neutr ...

s. The term "subnuclear zoo" was coined or popularized by

Robert Oppenheimer J. Robert Oppenheimer (; April 22, 1904 – February 18, 1967) was an American theoretical physicist. A professor of physics at the University of California, Berkeley, Oppenheimer was the wartime head of the Los Alamos Laboratory and is often ...

in 1956 at the VI Rochester

International Conference on High Energy Physics ICHEP or International Conference on High Energy Physics is one of the most prestigious international scientific conferences in the field of particle physics, bringing together leading theorists and experimentalists of the world. It was first held ...

.George Johnson (1999). ''Strange Beauty: Murray Gell-Mann and the Revolution in Twentieth-Century Physics'', p. 755, footnote 108: Oppenheimer coined the term "subnuclear zoo" in a public lecture at the Rochester VI conference; Sec VIII, p 1 of the proceedings.

See also

References

Further reading