Bottom quark
Makoto Kobayashi and Toshihide Maskawa (1973)[1] | |
---|---|
Discovered | Leon M. Lederman et al. (1977)[2] |
Mass | 4.18+0.04 −0.03 GeV/c2 (MS scheme)[3] 4.65+0.03 −0.03 ħ |
Weak isospin | LH: −+1/2, RH: 0 |
Weak hypercharge | LH: 1/3, RH: −+2/3 |
The bottom quark, beauty quark, or b quark, is an elementary particle of the third generation. It is a heavy quark with a charge of −1/3 e.
All quarks are described in a similar way by electroweak interaction 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 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
The evidence for the bottom quark was first obtained in 1977 by the
Kobayashi and Maskawa won the 2008 Nobel Prize in Physics for their explanation of CP-violation.[11][12]
While the name "beauty" is sometimes used, "bottom" became the predominant usage by analogy of "top" and "bottom" to "up" and "down".[citation needed]
Distinct character
The bottom quark's "bare" mass is around 4.18 GeV/c2[3] – 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 combination of high mass and low transition rate gives experimental
Hadrons containing bottom quarks
Some of the hadrons containing bottom quarks include:
- B mesons contain a bottom quark (or its antiparticle) and an up or down quark.
B
c and
B
s mesons contain a bottom quark along with a charm quark or strange quark respectively.- There are many χb(3P), the first particle discovered in LHC. These consist of a bottom quark and its antiparticle.
- Bottom baryons have been observed, and are named in analogy with strange baryons (e.g.
Λ0
b).
See also
References
- ^ hdl:2433/66179.
- ^ a b "Discoveries at Fermilab – Discovery of the Bottom Quark" (Press release). Fermilab. 7 August 1977. Retrieved 24 July 2009.
- ^ a b
M. Tanabashi et al. (Particle Data Group) (2018). "Review of Particle Physics". Physical Review D. 98 (3): 030001. hdl:10044/1/68623.
- ^ J. Beringer (Particle Data Group); et al. (2012). "PDGLive Particle Summary 'Quarks (u, d, s, c, b, t, b', t', Free)'" (PDF). Particle Data Group. Archived from the original (PDF) on 12 May 2013. Retrieved 18 December 2012.
- ^ Harari, H. (1975). "A new quark model for hadrons". .
- ^
Staley, K. W. (2004). The Evidence for the Top Quark. ISBN 978-0-521-82710-2.
- ^ Lederman, L. M. (2005). "Logbook: Bottom Quark". Symmetry Magazine. 2 (8). Archived from the original on 4 October 2006.
- ^
Herb, S. W.; Hom, D.; Lederman, L.; Sens, J.; Snyder, H.; OSTI 1155396.
- ^ G. Flügge (1978). "Particle Spectroscopy". Proceedings of the 19th International Conference on High Energy Physics (Tokyo): 793–810.
- ^ .
- ^ 2008 Physics Nobel Prize lecture by Makoto Kobayashi
- ^ 2008 Physics Nobel Prize lecture by Toshihide Maskawa
- ^ Nave, C.R. (ed.). "Transformation of Quark Flavors by the Weak Interaction". Department of Physics and Astronomy. HyperPhysics. Atlanta, GA: Georgia State University.
Further reading
- L. Lederman (1978). "The Upsilon Particle". .
- R. Nave. "Quarks". HyperPhysics. Georgia State University, Department of Physics and Astronomy. Retrieved 29 June 2008.
- A. Pickering (1984). Constructing Quarks. ISBN 978-0-226-66799-7.
- J. Yoh (1997). The Discovery of the b Quark at Fermilab in 1977: The Experiment Coordinator's Story (PDF). Proceedings of Twenty Beautiful Years of Bottom Physics. AIP Conference Proceedings. Vol. 424. pp. 29–42. doi:10.1063/1.55114.
- OCLC 636743000.
External links
- History of the discovery of the bottom quark / Upsilon meson Archived 24 August 2017 at the Wayback Machine