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 Colloquialism (), also called colloquial language, everyday language or general parlance, is the linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in conversa ...

to describe the relatively extensive list of known subatomic particles 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 purposes. The term ''zoological garden'' refers to zoo ...

. In the history of particle physics, 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 e ...

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, a ...

s. It was later discovered that they were not elementary particles, but rather composites of quarks. The set of particles believed today to be elementary is known as the Standard Model and includes quarks,

boson In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0,1,2 ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have odd half-integer spi ...

s and leptons. 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.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

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