
[[Image:First Gold Beam-Beam Collision Events at RHIC at 100 100 GeV c per beam recorded by STAR.jpg|thumb|right|450px|Particles explode from the collision point of two relativistic velocity (100 GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. Electrically charged particles are discernable by the elegant curves they trace in the detector's magnetic field.]] Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them. It is also called high energy physics, because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators. == Subatomic particles == Modern particle physics research is focused on subatomic particles, which have less structure than atoms. These include atomic constituents such as electrons, protons, and neutrons (protons and neutrons are actually composite particles, made up of quarks), particles produced by radiation and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles. Strictly speaking, the term ''particle'' is something of a misnomer. The objects studied by particle physics obey the principles of quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others. Theoretically, they are described neither as waves nor as particles, but as mathematical formulation of quantum mechanics in an abstract Hilbert space. For a more detailed explanation, see quantum field theory. Following the convention of particle physicists, we will use "elementary particles" to refer to objects such as electrons and photons, with the understanding that these "particles" display wave-like properties as well. All the particles observed to date have been catalogued in a quantum field theory called the Standard Model, which is often regarded as particle physics' best achievement to date. The model contains 47 species of elementary particles, some of which can combine to form composite particles, accounting for the hundreds of other species of particles discovered since the 1960s. The Standard Model has been found to agree with almost all the experimental tests conducted to date. However, most particle physicists believe that it is an incomplete description of Nature, and that a more fundamental theory awaits discovery. In recent years, measurements of neutrino mass have provided the first experimental deviations from the Standard Model. Particle physics has had a large impact on the philosophy of science. Some in the field still adhere to reductionism, an older concept which has been criticized by various philosophers and scientists. Part of the debate is described below. == History of particle physics == The idea that matter is composed of elementary particles dates to at least the 6th century BC. The philosophical doctrine of "atomism" was studied by Hellenic civilization philosophers such as Leucippus, Democritus, and Epicurus. Although Isaac Newton in the 17th century thought that matter was made up of particles, it was John Dalton who formally stated in 1802 that everything is made from tiny atoms. Dmitri Mendeleev's first periodic table in 1869 helped cement the view, prevalent throughout the 19th century, that matter was made of atoms. Work by J.J. Thomson established that atoms are composed of light electrons and massive protons. Ernest Rutherford established that the protons are concentrated in a compact nucleus. The nucleus was initially thought to be composed of protons and confined electrons (in order to explain the difference between nuclear charge and mass number), but was later found to be composed of protons and neutrons. The 20th century explorations of nuclear physics and quantum physics, culminating with proofs of nuclear fission and nuclear fusion, gave rise to an active industry of generating one atom from another, even rendering possible (although not profitable) the transmutation of lead into gold. These theories successfully predicted nuclear weapons. Throughout the 1950s and 1960s, a bewildering variety of particles was found in scattering experiments. This was referred to as the "particle zoo". This term was deprecated after the formulation of the Standard Model during the 1970s in which the large number of particles was explained as combinations of a (relatively) small number of fundamental particles. == The Standard Model of particle physics == The current state of the classification of elementary particles is the Standard Model. It describes the strong nuclear force, weak nuclear force, and electromagnetism fundamental forces, using mediating gauge bosons. The species of gauge bosons are the photon, W boson and Z bosons, and the gluons. The model also contains 24 fundamental particles, which are the constituents of matter. Finally, it predicts the existence of a type of boson known as the Higgs boson, which has yet to be discovered. == Experimental particle physics == In particle physics, the major international collaborations are: * CERN, located on the French-Swiss border near Geneva. Its main facilities are LEP, the Large Electron Positron collider (stopped in 2001, now dismantled); SPS, or the Super Proton Synchrotron; LHC, or Large Hadron Collider (under construction). * DESY, located in Hamburg, Germany. Its main facility is Hadron Elektron Ring Anlage, which collides electron or positron and proton. * SLAC, located near Palo Alto, USA. Its main facility is PEP-II, which collides electron and positron. * Fermilab, located near Chicago, USA. Its main facility is the Tevatron, which collides proton and proton. * Brookhaven National Laboratory, located on Long Island, USA. Its main facility is the [http://www.rhic.bnl.gov Relativistic Heavy Ion Collider], which collides heavy ion such as gold ions (it is the first heavy ion collider) and proton. * [http://www.inp.nsk.su Budker Institute of Nuclear Physics (Novosibirsk, Russia)] * [http://www.kek.jp/intra-e/ KEK] The High Energy Accelerator Research Organization of Japan located in Tsukuba, Japan. It is the home of a number of interesting experiments such as [http://neutrino.kek.jp/ K2K], a neutrino oscillation experiment and [http://belle.kek.jp/ Belle], an experiment measuring the CP-symmetry violation in the B-meson. Many other particle accelerator exist. ==Theoretical particle physics== Theoretical particle physics attempts to develop the models, theoretical framework, and mathematical tools to understand current experiments and make predictions for future experiments. See also theoretical physics. There are several major efforts in theoretical particle physics today and each includes a range of different activities. The efforts in each area are interrelated. One of the major activities in theoretical particle physics is the attempt to better understand the standard model and its tests. By extracting the parameters of the standard model from experiments with less uncertainty, this work probes the limits of the standard model and therefore expands our understanding of nature. These efforts are made challenging by the difficult nature of calculating many quantities in quantum chromodynamics. Some theorists making these efforts refer to themselves as phenomenologists and may use the tools of effective field theory. Others make use of lattice field theory and call themselves lattice theorists. Another major effort is in model building where model builders develop ideas for what physics may lie beyond the standard model (at higher energies or smaller distances). This work is often motivated by the hierarchy problem and is constrained by existing experimental data. It may involve work on supersymmetry, alternatives to the Higgs mechanism, Randall-Sundrum models, Preon theory, combinations of these, or other ideas. A third major effort in theoretical particle physics is string theory. String theorists attempt to construct a unified description of quantum mechanics and general relativity by building a theory based on small strings, and branes rather than particles. If the theory is successful in this, it may be considered a "Theory of Everything". There are also other areas of work in theoretical particle physics ranging from particle cosmology to loop quantum gravity. This divide of efforts in particle physics is reflected in the names of categories on the preprint archive[http://www.arxiv.org]: hep-th(theory), hep-ph (phenomenology), hep-ex (experiments), hep-lat(lattice gauge theory). == Particle physics and reductionism == Throughout the development of particle physics, there have been many objections to the extreme scientific reductionism (or ''greedy reductionism'') approach of attempting to explain ''everything'' in terms of elementary particles and their interaction. These objections have been raised by people from an wide array of fields, including many modern particle physicists, solid state physics, chemistry, biology, and metaphysical holism. While the Standard Model itself is not challenged, it is contended that the properties of elementary particles are no more (or less) fundamental science than the emergence properties of atoms and molecules, and especially statistically large ensembles of those. Some critics of reductionism claim that even a complete knowledge of the underlying elementary particles will not lend a thorough understanding of more complicated natural processes, while others doubt that a complete knowledge of particle behavior (as part of a larger process) could even be attained, thanks to quantum indeterminacy. Reductionists typically claim that all progress in the sciences has involved reductionism to some extent. == Public policy and particle physics == Experimental results in particle physics are often obtained using enormous particle accelerators which are very expensive (typically several billion US dollars) and require large amounts of government funding. Because of this, particle physics research involves issues of public policy. Many have argued that the potential advances do not justify the money spent, and that in fact particle physics takes money away from more important research and education efforts. In 1993, the US Congress stopped the Superconducting Super Collider because of similar concerns, after US$2 billion had already been spent on its construction. Many scientists, both supporters and opponents of the SSC, believe that the decision to stop construction of the SSC was due in part to the end of the Cold War which removed scientific competition with the Soviet Union as a rationale to spend large amounts of money on the SSC. Some within the scientific community believe that particle physics has also been adversely affected by the aging population. The belief is that the aging population is much more concerned with immediate issues of their health and their parents' health and that this has driven scientific funding away from physics toward the biological and health sciences. In addition, many opponents question the ability of any single country to support the expense of particle physics results and fault the SSC for not seeking greater international funding. Proponents of particle accelerators hold that the investigation of the most basic theories deserves adequate funding, and that this funding benefits other fields of science in various ways. They point out that all accelerators today are international projects and question the claim that money not spent on accelerators would then necessarily be used for other scientific or educational purposes. == The future of particle physics == Particle physicists internationally agree on the most important goals of particle physics research in the near and intermediate future. A (relatively) near term goal is the completion of the LHC in 2007 and subsequent search for the Higgs boson and SUSY. An intermediate goal is the construction of the International Linear Collider (ILC). A decision for the technology has been taken in August 2004, but the site has still to be agreed upon. Experimentally, the ILC is meant to complement the LHC. While the LHC is better suited for the discovery of new particles, the ILC will allow precise measurements of the properties of these particles. Other important goals in particle physics are the determination of the neutrino masses and the clarification of the existence of double beta decay of the proton. These measurements will be made at non-collider experiments. ==See also== *Atomic physics *Subatomic particle *Fundamental particle *List of particles ==External links== *[http://www.interactions.org/ Particle Physics News and Resources] *[http://www.arxiv.org/ ARXIV.ORG preprint server] *[http://particleadventure.org/particleadventure/frameless/credits.html ''The Particle Adventure'' educational project sponsored by the Particle Data Group of the Lawrence Berkeley National Laboratory (LBNL) ] *[http://www.singinst.org/GISAI/meta/glossary.html GISAI glossary, Yudkowsky] *[http://www.bu.edu/wcp/Papers/Reli/ReliGrue.htm "Philosophy Redivivus? Science, Ethics, and Faith"] *[http://www.schoolscience.co.uk/content/4/physics/particles/particlesdiscover1.html History of particle physics] * ''Introduction to Particle Physics'' by Matthew Nobes (published on Kuro5hin): **[http://www.kuro5hin.org/story/2002/5/1/3712/31700 Part 1] **[http://www.kuro5hin.org/story/2002/5/14/19363/8142 Part 2] **[http://www.kuro5hin.org/story/2002/7/15/173318/784 Part 3a] **[http://www.kuro5hin.org/story/2002/8/21/195035/576 Part 3b] * [http://www-spires.slac.stanford.edu/spires/hep/ High-Energy Physics Literature Database] * [http://nac21.uv.es ArrXiv: Full PDF collection of Phenomenology High Energy Physics] Particle physics Academic disciplines la:Physica particularum minimarum vi:Vật lý hạt
Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them. It is also called high energy physics, because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators. ''See Particle physics for more.'' Physics
''Old talk (prior to April 2004) archived in Talk:Particle physics/archive 1.'' ==Chart== Does wiki already have a chart like this [http://home.fnal.gov/~dawson/themes/backgrounds/800/elementary.particles.jpg]? I think it would make a nice addition to this (and other) articles.--User:Deglr6328 07:38, 18 Mar 2005 (UTC) =="Particle physics" or "Particle Physics"== Should this article be redirected from "Particle physics" to "Particle Physics"? User:Irpen 23:05, May 23, 2005 (UTC) :Please don't redirect. "Particle physics" is in line with Wikipedia's policies on capitalization of article names. -- User:CYD ::I sure won't if you say so. I just asked. User:Irpen
I moved this category to :Category:Physics from :Category:Quantum mechanics, because I believe they are rather distinct fields of physics. User:Karol Langner 07:24, Jun 16, 2005 (UTC)
See other meanings of words starting from letter:
Words begining with Particle_physics:
Particle_physics
Particle_physics
Particle_physics
Particle_physics
Particle_physics/archive_1
Particle_Physics_and_Astronomy_Research_Council
Particle_physics_foundation_ontology
Particle_physics_foundation_ontology
Particle_physics_standard_model
Particle physics
[[Image:First Gold Beam-Beam Collision Events at RHIC at 100 100 GeV c per beam recorded by STAR.jpg|thumb|right|450px|Particles explode from the collision point of two relativistic velocity (100 GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. Electrically charged particles are discernable by the elegant curves they trace in the detector's magnetic field.]] Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them. It is also called high energy physics, because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators. == Subatomic particles == Modern particle physics research is focused on subatomic particles, which have less structure than atoms. These include atomic constituents such as electrons, protons, and neutrons (protons and neutrons are actually composite particles, made up of quarks), particles produced by radiation and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles. Strictly speaking, the term ''particle'' is something of a misnomer. The objects studied by particle physics obey the principles of quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others. Theoretically, they are described neither as waves nor as particles, but as mathematical formulation of quantum mechanics in an abstract Hilbert space. For a more detailed explanation, see quantum field theory. Following the convention of particle physicists, we will use "elementary particles" to refer to objects such as electrons and photons, with the understanding that these "particles" display wave-like properties as well. All the particles observed to date have been catalogued in a quantum field theory called the Standard Model, which is often regarded as particle physics' best achievement to date. The model contains 47 species of elementary particles, some of which can combine to form composite particles, accounting for the hundreds of other species of particles discovered since the 1960s. The Standard Model has been found to agree with almost all the experimental tests conducted to date. However, most particle physicists believe that it is an incomplete description of Nature, and that a more fundamental theory awaits discovery. In recent years, measurements of neutrino mass have provided the first experimental deviations from the Standard Model. Particle physics has had a large impact on the philosophy of science. Some in the field still adhere to reductionism, an older concept which has been criticized by various philosophers and scientists. Part of the debate is described below. == History of particle physics == The idea that matter is composed of elementary particles dates to at least the 6th century BC. The philosophical doctrine of "atomism" was studied by Hellenic civilization philosophers such as Leucippus, Democritus, and Epicurus. Although Isaac Newton in the 17th century thought that matter was made up of particles, it was John Dalton who formally stated in 1802 that everything is made from tiny atoms. Dmitri Mendeleev's first periodic table in 1869 helped cement the view, prevalent throughout the 19th century, that matter was made of atoms. Work by J.J. Thomson established that atoms are composed of light electrons and massive protons. Ernest Rutherford established that the protons are concentrated in a compact nucleus. The nucleus was initially thought to be composed of protons and confined electrons (in order to explain the difference between nuclear charge and mass number), but was later found to be composed of protons and neutrons. The 20th century explorations of nuclear physics and quantum physics, culminating with proofs of nuclear fission and nuclear fusion, gave rise to an active industry of generating one atom from another, even rendering possible (although not profitable) the transmutation of lead into gold. These theories successfully predicted nuclear weapons. Throughout the 1950s and 1960s, a bewildering variety of particles was found in scattering experiments. This was referred to as the "particle zoo". This term was deprecated after the formulation of the Standard Model during the 1970s in which the large number of particles was explained as combinations of a (relatively) small number of fundamental particles. == The Standard Model of particle physics == The current state of the classification of elementary particles is the Standard Model. It describes the strong nuclear force, weak nuclear force, and electromagnetism fundamental forces, using mediating gauge bosons. The species of gauge bosons are the photon, W boson and Z bosons, and the gluons. The model also contains 24 fundamental particles, which are the constituents of matter. Finally, it predicts the existence of a type of boson known as the Higgs boson, which has yet to be discovered. == Experimental particle physics == In particle physics, the major international collaborations are: * CERN, located on the French-Swiss border near Geneva. Its main facilities are LEP, the Large Electron Positron collider (stopped in 2001, now dismantled); SPS, or the Super Proton Synchrotron; LHC, or Large Hadron Collider (under construction). * DESY, located in Hamburg, Germany. Its main facility is Hadron Elektron Ring Anlage, which collides electron or positron and proton. * SLAC, located near Palo Alto, USA. Its main facility is PEP-II, which collides electron and positron. * Fermilab, located near Chicago, USA. Its main facility is the Tevatron, which collides proton and proton. * Brookhaven National Laboratory, located on Long Island, USA. Its main facility is the [http://www.rhic.bnl.gov Relativistic Heavy Ion Collider], which collides heavy ion such as gold ions (it is the first heavy ion collider) and proton. * [http://www.inp.nsk.su Budker Institute of Nuclear Physics (Novosibirsk, Russia)] * [http://www.kek.jp/intra-e/ KEK] The High Energy Accelerator Research Organization of Japan located in Tsukuba, Japan. It is the home of a number of interesting experiments such as [http://neutrino.kek.jp/ K2K], a neutrino oscillation experiment and [http://belle.kek.jp/ Belle], an experiment measuring the CP-symmetry violation in the B-meson. Many other particle accelerator exist. ==Theoretical particle physics== Theoretical particle physics attempts to develop the models, theoretical framework, and mathematical tools to understand current experiments and make predictions for future experiments. See also theoretical physics. There are several major efforts in theoretical particle physics today and each includes a range of different activities. The efforts in each area are interrelated. One of the major activities in theoretical particle physics is the attempt to better understand the standard model and its tests. By extracting the parameters of the standard model from experiments with less uncertainty, this work probes the limits of the standard model and therefore expands our understanding of nature. These efforts are made challenging by the difficult nature of calculating many quantities in quantum chromodynamics. Some theorists making these efforts refer to themselves as phenomenologists and may use the tools of effective field theory. Others make use of lattice field theory and call themselves lattice theorists. Another major effort is in model building where model builders develop ideas for what physics may lie beyond the standard model (at higher energies or smaller distances). This work is often motivated by the hierarchy problem and is constrained by existing experimental data. It may involve work on supersymmetry, alternatives to the Higgs mechanism, Randall-Sundrum models, Preon theory, combinations of these, or other ideas. A third major effort in theoretical particle physics is string theory. String theorists attempt to construct a unified description of quantum mechanics and general relativity by building a theory based on small strings, and branes rather than particles. If the theory is successful in this, it may be considered a "Theory of Everything". There are also other areas of work in theoretical particle physics ranging from particle cosmology to loop quantum gravity. This divide of efforts in particle physics is reflected in the names of categories on the preprint archive[http://www.arxiv.org]: hep-th(theory), hep-ph (phenomenology), hep-ex (experiments), hep-lat(lattice gauge theory). == Particle physics and reductionism == Throughout the development of particle physics, there have been many objections to the extreme scientific reductionism (or ''greedy reductionism'') approach of attempting to explain ''everything'' in terms of elementary particles and their interaction. These objections have been raised by people from an wide array of fields, including many modern particle physicists, solid state physics, chemistry, biology, and metaphysical holism. While the Standard Model itself is not challenged, it is contended that the properties of elementary particles are no more (or less) fundamental science than the emergence properties of atoms and molecules, and especially statistically large ensembles of those. Some critics of reductionism claim that even a complete knowledge of the underlying elementary particles will not lend a thorough understanding of more complicated natural processes, while others doubt that a complete knowledge of particle behavior (as part of a larger process) could even be attained, thanks to quantum indeterminacy. Reductionists typically claim that all progress in the sciences has involved reductionism to some extent. == Public policy and particle physics == Experimental results in particle physics are often obtained using enormous particle accelerators which are very expensive (typically several billion US dollars) and require large amounts of government funding. Because of this, particle physics research involves issues of public policy. Many have argued that the potential advances do not justify the money spent, and that in fact particle physics takes money away from more important research and education efforts. In 1993, the US Congress stopped the Superconducting Super Collider because of similar concerns, after US$2 billion had already been spent on its construction. Many scientists, both supporters and opponents of the SSC, believe that the decision to stop construction of the SSC was due in part to the end of the Cold War which removed scientific competition with the Soviet Union as a rationale to spend large amounts of money on the SSC. Some within the scientific community believe that particle physics has also been adversely affected by the aging population. The belief is that the aging population is much more concerned with immediate issues of their health and their parents' health and that this has driven scientific funding away from physics toward the biological and health sciences. In addition, many opponents question the ability of any single country to support the expense of particle physics results and fault the SSC for not seeking greater international funding. Proponents of particle accelerators hold that the investigation of the most basic theories deserves adequate funding, and that this funding benefits other fields of science in various ways. They point out that all accelerators today are international projects and question the claim that money not spent on accelerators would then necessarily be used for other scientific or educational purposes. == The future of particle physics == Particle physicists internationally agree on the most important goals of particle physics research in the near and intermediate future. A (relatively) near term goal is the completion of the LHC in 2007 and subsequent search for the Higgs boson and SUSY. An intermediate goal is the construction of the International Linear Collider (ILC). A decision for the technology has been taken in August 2004, but the site has still to be agreed upon. Experimentally, the ILC is meant to complement the LHC. While the LHC is better suited for the discovery of new particles, the ILC will allow precise measurements of the properties of these particles. Other important goals in particle physics are the determination of the neutrino masses and the clarification of the existence of double beta decay of the proton. These measurements will be made at non-collider experiments. ==See also== *Atomic physics *Subatomic particle *Fundamental particle *List of particles ==External links== *[http://www.interactions.org/ Particle Physics News and Resources] *[http://www.arxiv.org/ ARXIV.ORG preprint server] *[http://particleadventure.org/particleadventure/frameless/credits.html ''The Particle Adventure'' educational project sponsored by the Particle Data Group of the Lawrence Berkeley National Laboratory (LBNL) ] *[http://www.singinst.org/GISAI/meta/glossary.html GISAI glossary, Yudkowsky] *[http://www.bu.edu/wcp/Papers/Reli/ReliGrue.htm "Philosophy Redivivus? Science, Ethics, and Faith"] *[http://www.schoolscience.co.uk/content/4/physics/particles/particlesdiscover1.html History of particle physics] * ''Introduction to Particle Physics'' by Matthew Nobes (published on Kuro5hin): **[http://www.kuro5hin.org/story/2002/5/1/3712/31700 Part 1] **[http://www.kuro5hin.org/story/2002/5/14/19363/8142 Part 2] **[http://www.kuro5hin.org/story/2002/7/15/173318/784 Part 3a] **[http://www.kuro5hin.org/story/2002/8/21/195035/576 Part 3b] * [http://www-spires.slac.stanford.edu/spires/hep/ High-Energy Physics Literature Database] * [http://nac21.uv.es ArrXiv: Full PDF collection of Phenomenology High Energy Physics] Particle physics Academic disciplines la:Physica particularum minimarum vi:Vật lý hạt
Particle physics
Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them. It is also called high energy physics, because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators. ''See Particle physics for more.'' Physics
Particle physics
''Old talk (prior to April 2004) archived in Talk:Particle physics/archive 1.'' ==Chart== Does wiki already have a chart like this [http://home.fnal.gov/~dawson/themes/backgrounds/800/elementary.particles.jpg]? I think it would make a nice addition to this (and other) articles.--User:Deglr6328 07:38, 18 Mar 2005 (UTC) =="Particle physics" or "Particle Physics"== Should this article be redirected from "Particle physics" to "Particle Physics"? User:Irpen 23:05, May 23, 2005 (UTC) :Please don't redirect. "Particle physics" is in line with Wikipedia's policies on capitalization of article names. -- User:CYD ::I sure won't if you say so. I just asked. User:Irpen
Particle physics
I moved this category to :Category:Physics from :Category:Quantum mechanics, because I believe they are rather distinct fields of physics. User:Karol Langner 07:24, Jun 16, 2005 (UTC)
See other meanings of words starting from letter:
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Particle_physics
Particle_physics
Particle_physics
Particle_physics
Particle_physics/archive_1
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Particle_physics_foundation_ontology
Particle_physics_foundation_ontology
Particle_physics_standard_model
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