Difference between revisions of "Antiproton" - New World Encyclopedia

	AntiProton
	; The quark structure of the proton.
Classification:	Baryon

Latest revision as of 01:57, 9 January 2023

Antimatter

Overview

Annihilation

Devices

Particle accelerator
Penning trap

Antiparticles

Positron
Antiproton
Antineutron

Uses

Scientific Bodies

ALPHA Collaboration
ATHENA
ATRAP
CERN

People

Paul Dirac
Carl Anderson
Andrei Sakharov

edit

An antiproton (symbol p, pronounced p-bar) is the antiparticle of the proton. An antiproton is relatively stable, but it is typically short-lived because any collision with a proton will cause both particles to be annihilated in a burst of energy. It was discovered in 1955 by University of California, Berkeley physicists Emilio Segrè and Owen Chamberlain, for which they were awarded the 1959 Nobel Prize in Physics. At CERN in Geneva, Switzerland, and Fermilab in Batavia, Illinois, antiprotons are routinely produced and used for scientific research.

Properties

Theoretically, an antiproton consists of two anti-up quarks and one anti-down quark, symbolized as u u d.

The properties of the antiproton are predicted by CPT symmetry^[1] to be exactly related to those of the proton. In particular, CPT symmetry predicts the mass and lifetime of the antiproton to be the same as those of the proton, and the electric charge and magnetic moment of the antiproton to be opposite in sign and equal in magnitude to those of the proton.

In mid-June 2006, scientists at CERN (the European Organization for Nuclear Research, or, in French, Organisation Européenne pour la Recherche Nucléaire) succeeded in determining the mass of the antiproton, which they measured at 1,836.153674(5) times more massive than an electron. This is exactly the same as the mass of a "regular" proton, as predicted. The formation of antimatter is related to questions about what happened around the time of the Big Bang, and why such a small amount of antimatter remains in our Solar System today.

Artificial production

The formation of antiprotons requires energy equivalent to a temperature of ten trillion K (10¹³ K), which is not attained under most natural conditions. However, at CERN (the European Organization for Nuclear Research, or, in French, Organisation Européenne pour la Recherche Nucléaire), protons are accelerated in the Proton Synchrotron (PS) to an energy of 26 GeV, and then smashed into an iridium rod. The protons bounce off the iridium nuclei with enough energy for matter to be created. A range of particles and antiparticles are formed, and the antiprotons are separated off using magnets in vacuum.

Occurrence in nature

Antiprotons have been detected in cosmic rays for over 25 years, first by balloon-borne experiments and more recently by satellite-based detectors. The standard picture for their presence in cosmic rays is that they are produced in collisions of cosmic ray protons with nuclei in the interstellar medium, via the reaction:

p A → p p p A

The secondary antiprotons (p) then propagate through the galaxy, confined by the galactic magnetic fields. Their energy spectrum is modified by collisions with other atoms in the interstellar medium, and antiprotons can also be lost by "leaking out" of the galaxy.

The antiproton cosmic ray energy spectrum is now measured reliably and is consistent with this standard picture of antiproton production by cosmic ray collisions.^[2] This sets upper limits on the number of antiprotons that could be produced in exotic ways, such as from annihilation of supersymmetric dark matter particles in the galaxy, or from the evaporation of primordial black holes. This also provides a lower limit on the antiproton lifetime of about one to ten million years. Since the galactic storage time of antiprotons is about ten million years, an intrinsic decay lifetime would modify the galactic residence time and distort the spectrum of cosmic ray antiprotons. This is significantly more stringent than the best laboratory measurements of the antiproton lifetime:

LEAR collaboration at CERN: 0.8 year
Antihydrogen Penning trap of Gabrielse et al: 0.28 year^[3]
APEX collaboration at Fermilab: 50,000 years for p → μ⁻ + X and 300,000 years for p → e⁻ + γ

Experimental detection in cosmic rays

Recent experiments for antiproton detection in cosmic rays include the following:

BESS: balloon-borne experiment, flown in 1993, 1995, and 1997.
CAPRICE: balloon-borne experiment, flown in 1994.^[4]
HEAT: balloon-borne experiment, flown in 2000.
AMS: space-based experiment, prototype flown on the space shuttle in 1998, intended for the International Space Station but not yet launched.
PAMELA: satellite experiment to detect cosmic rays and antimatter from space, launched in June 2006.

Uses

Antiprotons are routinely produced at Fermilab for collider physics operations in the Tevatron, where they are collided with protons. The use of antiprotons allows for a higher average energy of collisions between quarks and antiquarks than would be possible in proton-proton collisions. The theoretical basis for this is that the valence quarks in the proton and the valence antiquarks in the antiproton tend to carry the largest fraction of the proton or antiproton's momentum.

Notes

↑ CPT symmetry is a fundamental symmetry of physical laws under transformations that involve the inversions of electric charge, parity, and time simultaneously. CPT symmetry is a basic consequence of quantum field theory and no violations of it have been detected.
↑ Dallas C. Kennedy (2000), Cosmic Ray Antiprotons Astrophysics. (doi=10.1117/12.253971). Retrieved October 9, 2008.
↑ C. Caso, et al. (Particle Data Group) (1998), B^± Eur. Phys. J. C3:613.
↑ Cosmic AntiParticle Ring Imaging Cherenkov Experiment (CAPRICE) Retrieved October 9, 2008.

References
ISBN links support NWE through referral fees

Forward, Robert L. 2001. Mirror Matter: Pioneering Antimatter Physics. Lincoln, NE: Backinprint.com. ISBN 0595198171
Fraser, Gordon. 2002. Antimatter: The Ultimate Mirror. Cambridge, UK: Cambridge University Press. ISBN 0521893097
Kondo, K., and S. Kim. 1994. 9th Topical Workshop on Proton-Antiproton Collider Physics. Frontier Science Series No. 11. Tokyo, Japan: Universal Academy Press. ASIN B000RFVPI4
Santilli, Ruggero Maria. 2006. Isodual Theory of Antimatter: with applications to Antigravity, Grand Unification and Cosmology (Fundamental Theories of Physics). New York, NY: Springer. ISBN 1402045174

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Antiproton ^history

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[1] CPT symmetry is a fundamental symmetry of physical laws under transformations that involve the inversions of electric charge, parity, and time simultaneously. CPT symmetry is a basic consequence of quantum field theory and no violations of it have been detected.

[2] Dallas C. Kennedy (2000), Cosmic Ray Antiprotons Astrophysics. (doi=10.1117/12.253971). Retrieved October 9, 2008.

[3] C. Caso, et al. (Particle Data Group) (1998), B^± Eur. Phys. J. C3:613.

[4] Cosmic AntiParticle Ring Imaging Cherenkov Experiment (CAPRICE) Retrieved October 9, 2008.

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@@ Line 1: / Line 1: @@
-The '''antiproton''' ({{SubatomicParticle|Antiproton}}, pronounced ''p-bar'') is the [[antiparticle]] of the [[proton]]. Antiprotons are stable, but they are typically short-lived since any collision with a proton will cause both particles to be [[annihilation|annihilated]] in a burst of energy. It was discovered in [[1955]] by [[University of California, Berkeley]] [[physicist]]s [[Emilio Segrè]] and [[Owen Chamberlain]], for which they were awarded the [[1959]] [[Nobel Prize in Physics]]. An antiproton consists of two anti-up [[quarks]] and one anti-down quark ({{SubatomicParticle|link=yes|Up antiquark}}{{SubatomicParticle|link=yes|Up antiquark}}{{SubatomicParticle|link=yes|Down antiquark}}).
+{{Copyedited}}{{Images OK}}{{Approved}}
 {{antimatter}}
+An '''antiproton''' (symbol {{SubatomicParticle|Antiproton}}, pronounced ''p-bar'') is the [[antiparticle]] of the [[proton]]. An antiproton is relatively stable, but it is typically short-lived because any collision with a proton will cause both particles to be [[annihilation|annihilated]] in a burst of energy. It was discovered in 1955 by [[University of California, Berkeley]] [[physicist]]s [[Emilio Segrè]] and [[Owen Chamberlain]], for which they were awarded the 1959 [[Nobel Prize in Physics]]. At [[CERN]] in [[Geneva]], [[Switzerland]], and [[Fermilab]] in Batavia, [[Illinois]], antiprotons are routinely produced and used for scientific research.
+{{toc}}
 {{Infobox Particle
 | bgcolour =
@@ Line 9: / Line 11: @@
 | caption = The quark structure of the proton.
 }}
+== Properties ==
-Their formation requires energy equivalent to a temperature of 10 trillion [[Kelvin|K]] (10<sup>13</sup> K), and [[Big Bang]]s aside, this does not tend to happen naturally. However, at [[CERN]], protons are accelerated in the Proton [[Synchrotron]] (PS) to an energy of 26 [[giga|G]][[electron volt|eV]], and then smashed into an [[iridium]] rod. The protons bounce off the iridium nuclei with [[mass-energy equivalence|enough energy for matter to be created]]. A range of particles and antiparticles are formed, and the antiprotons are separated off using magnets in [[vacuum]].
+Theoretically, an antiproton consists of two anti-up [[quarks]] and one anti-down quark, symbolized as {{SubatomicParticle|link=yes|Up antiquark}}{{SubatomicParticle|link=yes|Up antiquark}}{{SubatomicParticle|link=yes|Down antiquark}}.
-In mid-June 2006, CERN succeeded in determining the mass of the antiproton, which they measured at {{val|1836.153674|(5)}} times more massive than an [[electron]]. This is exactly the same as the mass of a "regular" proton, necessitating further research into the nature of difference between matter and anti-matter, in order to explain how our universe survived the [[Big Bang]] and why so little remains of [[antimatter]] today in our solar system.{{Fact|date=February 2007}}
+The properties of the antiproton are predicted by [[CPT symmetry]]<ref>CPT symmetry is a fundamental [[Symmetry in physics|symmetry]] of [[physical law]]s under [[transformation (mathematics)|transformation]]s that involve the inversions of [[electric charge]], [[parity (physics)|parity]], and [[time]] simultaneously. CPT symmetry is a basic consequence of [[quantum field theory]] and no violations of it have been detected.</ref> to be exactly related to those of the proton. In particular, CPT symmetry predicts the mass and lifetime of the antiproton to be the same as those of the proton, and the electric charge and magnetic moment of the antiproton to be opposite in sign and equal in magnitude to those of the proton.
+In mid-June 2006, scientists at [[CERN]] (the European Organization for Nuclear Research, or, in French, ''Organisation Européenne pour la Recherche Nucléaire'') succeeded in determining the mass of the antiproton, which they measured at {{val|1836.153674|(5)}} times more massive than an [[electron]]. This is exactly the same as the mass of a "regular" proton, as predicted. The formation of antimatter is related to questions about what happened around the time of the [[Big Bang]], and why such a small amount of antimatter remains in our Solar System today.
+== Artificial production ==
+The formation of antiprotons requires energy equivalent to a [[temperature]] of ten trillion [[Kelvin|K]] (10<sup>13</sup> K), which is not attained under most natural conditions. However, at [[CERN]] (the European Organization for Nuclear Research, or, in French, ''Organisation Européenne pour la Recherche Nucléaire''), protons are accelerated in the Proton [[Synchrotron]] (PS) to an energy of 26 [[giga|G]][[electron volt|eV]], and then smashed into an [[iridium]] rod. The protons bounce off the iridium nuclei with [[mass-energy equivalence|enough energy for matter to be created]]. A range of particles and antiparticles are formed, and the antiprotons are separated off using magnets in [[vacuum]].
 ==Occurrence in nature==
@@ Line 22: / Line 31: @@
 The secondary antiprotons ({{SubatomicParticle|Antiproton}}) then propagate through the [[galaxy]], confined by the galactic [[magnetic field]]s. Their energy spectrum is modified by collisions with other atoms in the interstellar medium, and antiprotons can also be lost by "leaking out" of the galaxy.
-The antiproton cosmic ray energy spectrum is now measured reliably and is consistent with this standard picture of antiproton production by cosmic ray collisions.<ref>{{cite journal |last=Kennedy |first=Dallas C. |authorlink= |coauthors= |year=2000 |month= |title=Cosmic Ray Antiprotons |journal= |volume= 2806|issue= |pages= 113|id= |url=http://arxiv.org/abs/astro-ph/0003485v2 |accessdate= |quote=|doi=10.1117/12.253971 }}</ref> This sets upper limits on the number of antiprotons that could be produced in exotic ways, such as from annihilation of [[Supersymmetry|supersymmetric]] [[dark matter]] particles in the galaxy or from the [[Hawking radiation|evaporation]] of [[primordial black hole]]s. This also provides a lower limit on the antiproton lifetime of about 1-10 million years. Since the galactic storage time of antiprotons is about 10 million years, an intrinsic decay lifetime would modify the galactic residence time and distort the spectrum of cosmic ray antiprotons. This is significantly more stringent than the best laboratory measurements of the antiproton lifetime:
+The antiproton cosmic ray energy spectrum is now measured reliably and is consistent with this standard picture of antiproton production by cosmic ray collisions.<ref>Dallas C. Kennedy (2000), [http://arxiv.org/abs/astro-ph/0003485v2 Cosmic Ray Antiprotons] ''Astrophysics''. (doi=10.1117/12.253971). Retrieved October 9, 2008.</ref> This sets upper limits on the number of antiprotons that could be produced in exotic ways, such as from annihilation of [[Supersymmetry|supersymmetric]] [[dark matter]] particles in the galaxy, or from the [[Hawking radiation|evaporation]] of [[primordial black hole]]s. This also provides a lower limit on the antiproton lifetime of about one to ten million years. Since the galactic storage time of antiprotons is about ten million years, an intrinsic decay lifetime would modify the galactic residence time and distort the spectrum of cosmic ray antiprotons. This is significantly more stringent than the best laboratory measurements of the antiproton lifetime:
 * [[LEAR]] collaboration at [[CERN]]: {{val|0.08|u=year}}
-* [[Antihydrogen]] [[Penning trap]] of Gabrielse et al: {{val|0.28|u=year}} <ref>{{cite journal |last=Caso |first=C. |authorlink= |coauthors=''et al.'' |year=1998 |month= |title=[[Particle Data Group]] |journal=Eur. Phys. J. |volume=C3 |issue= |pages=613 |id= |url=http://pdg.ihep.su/1999/s041.pdf |accessdate= |quote= }}</ref>
+* [[Antihydrogen]] [[Penning trap]] of Gabrielse et al: {{val|0.28|u=year}}<ref>C. Caso, et al. (Particle Data Group) (1998), B<sup>±</sup> ''Eur. Phys. J.'' C3:613.</ref>
 * APEX collaboration at [[Fermilab]]: {{val|50000|u=years}} for {{SubatomicParticle|Antiproton}} → {{SubatomicParticle|link=yes|Muon}} + X<!-- What is "X"?? —> and {{val|300000|u=years}} for {{SubatomicParticle|Antiproton}} → {{SubatomicParticle|link=yes|Electron}} + {{SubatomicParticle|link=yes|Gamma}}
-The properties of the antiproton are predicted by [[CPT symmetry]] to be exactly related to those of the proton. In particular, CPT symmetry predicts the mass and lifetime of the antiproton to be the same as those of the proton, and the electric charge and magnetic moment of the antiproton to be opposite in sign and equal in magnitude to those of the proton. CPT symmetry is a basic consequence of [[quantum field theory]] and no violations of it have ever been detected.
+===Experimental detection in cosmic rays===
-===List of recent antiproton cosmic ray detection experiments===
+Recent experiments for antiproton detection in cosmic rays include the following:
 * [[BESS]]: balloon-borne experiment, flown in 1993, 1995, and 1997.
-* CAPRICE: balloon-borne experiment, flown in 1994.<ref>[http://ida1.physik.uni-siegen.de/caprice.html Caprice Experiment<!-- Bot generated title —>]</ref>
+* CAPRICE: balloon-borne experiment, flown in 1994.<ref>[http://ida1.physik.uni-siegen.de/caprice.html Cosmic AntiParticle Ring Imaging Cherenkov Experiment (CAPRICE)] Retrieved October 9, 2008.</ref>
 * HEAT: balloon-borne experiment, flown in 2000.
 * [[Alpha Magnetic Spectrometer|AMS]]: space-based experiment, prototype flown on the [[space shuttle]] in 1998, intended for the [[International Space Station]] but not yet launched.
-* [[Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics|PAMELA]]: satellite experiment to detect cosmic rays and antimatter from space, launched June 2006.
+* [[Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics|PAMELA]]: satellite experiment to detect cosmic rays and antimatter from space, launched in June 2006.
 ==Uses==
-Antiprotons are routinely produced at [[Fermilab]] for collider physics operations in the [[Tevatron]], where they are collided with protons. The use of antiprotons allows for a higher average energy of collisions between [[quark]]s and [[antiquark]]s than would be possible in proton-proton collisions. This is because the [[valence quark]]s in the proton, and the valence antiquarks in the antiproton, [[Parton (particle physics)|tend to carry the largest fraction of the proton or antiproton's momentum]].
+Antiprotons are routinely produced at [[Fermilab]] for collider physics operations in the [[Tevatron]], where they are collided with protons. The use of antiprotons allows for a higher average energy of collisions between [[quark]]s and [[antiquark]]s than would be possible in proton-proton collisions. The theoretical basis for this is that the [[valence quark]]s in the proton and the valence antiquarks in the antiproton [[Parton (particle physics)|tend to carry the largest fraction of the proton or antiproton's momentum]].
+== See also ==
+* [[Antimatter]]
+* [[Elementary particle]]
+* [[Positron]]
+* [[Proton]]
+== Notes ==
+<references/>
 == References ==
-{{Reflist}}
-==See also==
+* Forward, Robert L. 2001. ''Mirror Matter: Pioneering Antimatter Physics.'' Lincoln, NE: Backinprint.com. ISBN 0595198171
-*[[Antimatter]]
+* Fraser, Gordon. 2002. ''Antimatter: The Ultimate Mirror.'' Cambridge, UK: Cambridge University Press. ISBN 0521893097
-*[[Antineutron]]
+* Kondo, K., and S. Kim. 1994. ''9th Topical Workshop on Proton-Antiproton Collider Physics''. Frontier Science Series No. 11. Tokyo, Japan: Universal Academy Press. {{ASIN|B000RFVPI4}}
-*[[Positron]]
+* Santilli, Ruggero Maria. 2006. ''Isodual Theory of Antimatter: with applications to Antigravity, Grand Unification and Cosmology (Fundamental Theories of Physics).'' New York, NY: Springer. ISBN 1402045174
-*[[List of particles]]
+----
 {{Particles}}

Particles in physics
elementary particles	Elementary fermions: Quarks: u · d · s · c · b · t • Leptons: e · μ · τ · ν_e · ν_μ · ν_τ Elementary bosons: Gauge bosons: γ · g · W^± · Z⁰ • Ghosts
Composite particles	Hadrons: Baryons(list)/Hyperons/Nucleons: p · n · Δ · Λ · Σ · Ξ · Ω · Ξ_b • Mesons(list)/Quarkonia: π · K · ρ · J/ψ · Υ Other: Atomic nucleus • Atoms • Molecules • Positronium
Hypothetical elementary particles	Superpartners: Axino · Dilatino · Chargino · Gluino · Gravitino · Higgsino · Neutralino · Sfermion · Slepton · Squark Other: Axion · Dilaton · Goldstone boson · Graviton · Higgs boson · Tachyon · X · Y · W' · Z'
Hypothetical composite particles	Exotic hadrons: Exotic baryons: Pentaquark • Exotic mesons: Glueball · Tetraquark Other: Mesonic molecule
Quasiparticles	Davydov soliton · Exciton · Magnon · Phonon · Plasmon · Polariton · Polaron

AntiProton
The quark structure of the proton.
Classification:	Baryon