The bottom quark or b quark, also known as the beauty quark, is a third-generation heavy quark with a charge of − ''e''. All quarks are described in a similar way by

electroweak In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very differe ...

and quantum chromodynamics, but the bottom quark has exceptionally low rates of transition to lower-mass quarks. The bottom quark is also notable because it is a product in almost all

top quark The top quark, sometimes also referred to as the truth quark, (symbol: t) is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs Boson. This coupling y_ is very close to unity; in the Standard ...

decays, and is a frequent decay product of the Higgs boson.

Name and history

The bottom quark was first described theoretically in 1973 by physicists Makoto Kobayashi and

Toshihide Maskawa was a Japanese theoretical physicist known for his work on CP-violation who was awarded one quarter of the 2008 Nobel Prize in Physics "for the discovery of the origin of the broken symmetry which predicts the existence of at least three famil ...

to explain

CP violation In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge symmetry) and P-symmetry ( parity symmetry). CP-symmetry states that the laws of physics should be th ...

. The name "bottom" was introduced in 1975 by

Haim Harari use both this parameter and , birth_date to display the person's date of birth, date of death, and age at death) --> , death_place = , death_cause = , body_discovered = , resting_place = , resting_place_coordinates ...

. The bottom quark was discovered in 1977 by the

Fermilab Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been opera ...

E288 experiment E, or e, is the fifth letter and the second vowel letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''e'' (pronounced ); plur ...

team led by

Leon M. Lederman Leon Max Lederman (July 15, 1922 – October 3, 2018) was an American experimental physicist who received the Nobel Prize in Physics in 1988, along with Melvin Schwartz and Jack Steinberger, for research on neutrinos. He also received the Wolf P ...

, when collisions produced

bottomonium In particle physics, quarkonium (from quark and -onium, pl. quarkonia) is a flavorless meson whose constituents are a heavy quark and its own antiquark, making it both a neutral particle and its own antiparticle. Light quarks Light quarks ( up ...

. Kobayashi and Maskawa won the 2008

Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...

for their explanation of CP-violation. While the name "beauty" is sometimes used, "bottom" became the predominant usage by analogy of "top" and "bottom" to "up" and "down".

Distinct character

The bottom quark's "bare" mass is around – a bit more than four times the mass of a proton, and many orders of magnitude larger than common "light" quarks. Although it almost exclusively transitions from or to a

, the bottom quark can decay into either an

up quark The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a significant constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quark ...

charm quark The charm quark, charmed quark or c quark (from its symbol, c) is the third-most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks. Examples of hadrons containin ...

via the

weak interaction In nuclear physics and particle physics, the weak interaction, which is also often called the weak force or weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction ...

. CKM matrix elements and specify the rates, where both these decays are suppressed, making lifetimes of most bottom particles (~10⁻¹² s) somewhat longer than those of charmed particles (~10⁻¹³ s), but shorter than those of strange particles (from ~10⁻¹⁰ to ~10⁻⁸ s). The combination of high mass and low transition rate gives experimental

collision In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...

byproducts containing a bottom quark a distinctive signature that makes them relatively easy to identify using a technique called " B-tagging". For that reason,

meson In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, ...

s containing the bottom quark are exceptionally long-lived for their mass, and are the easiest particles to use to investigate

. Such experiments are being performed at the BaBar, Belle and

LHCb The LHCb (Large Hadron Collider beauty) experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the paramet ...

experiments.

Hadrons containing bottom quarks

Some of the

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 containing bottom quarks include: *

B meson In particle physics, B mesons are mesons composed of a bottom antiquark and either an up (), down (), strange () or charm quark (). The combination of a bottom antiquark and a top quark is not thought to be possible because of the top quark' ...

s contain a bottom quark (or its

antiparticle In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antie ...

) and an up or

down quark The down quark or d quark (symbol: d) is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. Together with the up quark, it forms the neutrons (one up quark, two down quarks) and protons (two up ...

. * and mesons contain a bottom quark along with a

or strange quark respectively. *There are many

states, for example the meson and χ_b(3P), the first particle discovered in LHC. These consist of a bottom quark and its antiparticle. *Bottom

baryon In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classif ...

s have been observed, and are named in analogy with strange baryons (e.g. ).

References

External links

History of the discovery of the bottom quark / Upsilon meson
{{DEFAULTSORT:Bottom Quark Elementary particles Quarks

Name and history

Distinct character

Hadrons containing bottom quarks

See also

References

Further reading

External links