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Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. Electrically charged particles are discernible by the curves they trace in the detector's magnetic field.
Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. A relativistic particle is a particle which moves with a Relativistic speed; that is a Speed comparable to the Speed of light. Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 The STAR detector, which stands for Solenoidal Tracker at RHIC is one of the four experiments at the Relativistic Heavy Ion Collider (RHIC in Brookhaven National The Relativistic Heavy Ion Collider (RHIC pronounced like " Rick " ˈrɪk is a heavy- Ion Collider located at and operated by Brookhaven Electrically charged particles are discernible by the curves they trace in the detector's magnetic field.

Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Matter is commonly defined as being anything that has mass and that takes up space. Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy 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. Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. A collision is an isolated event in which two or more bodies (colliding bodies exert relatively strong forces on each other for a relatively short time Research in this area has produced a long list of particles. This is a list of the different types of particles known and hypothesized

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Subatomic Particles

Modern particle physics research is focused on subatomic particles, which have less structure than atoms. A subatomic particle is an elementary or composite Particle smaller than an Atom. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny These include atomic constituents such as electrons, protons, and neutrons (protons and neutrons are actually composite particles, made up of quarks), particles produced by radiative and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. In Particle physics, a radiative process refers to one Elementary particle emitting another and continuing to exist Scattering is a general physical process whereby some forms of Radiation, such as Light, Sound or moving particles for example are forced to deviate from In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 An exotic particle is a kind of theoretical particle said to exist by some areas of modern Physics, and whose alleged properties are extremely unusual

Strictly speaking, the term particle is a misnomer because the dynamics of particle physics are governed by quantum mechanics. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others (more technically they are described by state vectors in a Hilbert space; see quantum field theory). In Physics and Chemistry, wave–particle duality is the concept that all Matter and Energy exhibits both Wave -like and A wave is a disturbance that propagates through Space and Time, usually with transference of Energy. The mathematical formulation of quantum mechanics is the body of mathematical formalisms which permits a rigorous description of Quantum mechanics. This article assumes some familiarity with Analytic geometry and the concept of a limit. In quantum field theory (QFT the forces between particles are mediated by other particles Following the convention of particle physicists, "elementary particles" refer to objects such as electrons and photons, with the understanding that these "particles" display wave-like properties as well. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena

All the particles and their interactions observed to date can almost be described entirely by a quantum field theory called the Standard Model. In quantum field theory (QFT the forces between particles are mediated by other particles The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles The Standard Model has 40 species of elementary particles (24 fermions, 12 vector bosons, and 4 scalar bosons), which can combine to form composite particles, accounting for the hundreds of other species of particles discovered since the 1960s. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. A vector boson is a Boson with spin equal to one unit of \hbar ( Planck's constant divided by 2 \pi A scalar boson is a Boson with spin equal to zero Some Mesons are scalar bosons 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. Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object

Particle physics has had a large impact on the philosophy of science. Some particle physicists adhere to reductionism, a point of view that has been criticized and defended by philosophers and scientists. Reductionism can either mean (a an approach to understanding the nature of complex things by reducing them to the interactions of their parts or to simpler or more fundamental things Part of the debate is described below. [1][2][3][4]

History

The idea that all matter is composed of elementary particles dates to at least the 6th century BC. Matter is commonly defined as being anything that has mass and that takes up space. The philosophical doctrine of atomism was studied by ancient Greek philosophers such as Leucippus, Democritus, and Epicurus. In Natural philosophy, atomism is the theory that all the objects in the universe are composed of very small indestructible building blocks - Atoms Or stated in The term ancient Greece refers to the period of Greek history lasting from the Greek Dark Ages ca Philosophy is the study of general problems concerning matters such as existence knowledge truth beauty justice validity mind and language Leucippus or Leukippos ( Greek, first half of 5th century BC was among the earliest philosophers of Atomism, the idea that everything is composed entirely Democritus ( Greek:) was a pre-Socratic Greek Materialist Philosopher (born at Abdera in Thrace ca In the 19th century John Dalton, through his work on stoichiometry, concluded that each element of nature was composed of a single, unique type of particle. Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry is the Calculation of Quantitative (measurable Dalton and his contemporaries believed these were the fundamental particles of nature and thus named them atoms, after the Greek word atomos, meaning "indivisible". However, near the end of the century, physicists discovered that atoms were not, in fact, the fundamental particles of nature, but conglomerates of even smaller particles. The early 20th century explorations of nuclear physics and quantum physics culminated in proofs of nuclear fission in 1939 by Lise Meitner (based on experiments by Otto Hahn), and nuclear fusion by Hans Bethe in the same year. Nuclear physics is the field of Physics that studies the building blocks and interactions of Atomic nuclei. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing Free neutrons and other smaller nuclei which may Lise Meitner (7 or 17 November 1878 &ndash 27 October 1968 was an Austrian born later Swedish physicist who studied Radioactivity and Otto Hahn (8 March 1879 &ndash 28 July 1968 was a German Chemist who received the 1944 Nobel Prize in Chemistry for discovering Nuclear fission In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Hans Albrecht Bethe (/hans ˈalbʀɛçt ˈbeːtə/ ( July 2 1906 &ndash March 6, 2005) was a German - American Physicist These discoveries gave rise to an active industry of generating one atom from another, even rendering possible (although not profitable) the transmutation of lead into gold. Alchemy a part of the Occult Tradition is both a philosophy and a practice with an ultimately unknown aim involving the improvement of the alchemist as well as the making of They also led to the development of nuclear weapons. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Throughout the 1950s and 1960s, a bewildering variety of particles were 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 is a theory that describes three of the four known Fundamental interactions together with the Elementary particles

The Standard Model

Main article: Standard Model

The current state of the classification of elementary particles is the Standard Model. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles It describes the strong, weak, and electromagnetic fundamental forces, using mediating gauge bosons. In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature The species of gauge bosons are the gluons, W− and W+ and Z bosons, and the photons. Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the The W and Z bosons are the Elementary particles that mediate the Weak force. The W and Z bosons are the Elementary particles that mediate the Weak force. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The model also contains 24 fundamental particles, which are the constituents of matter. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Matter is commonly defined as being anything that has mass and that takes up space. Finally, it predicts the existence of a type of boson known as the Higgs boson, which has yet to be discovered. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics

Experiment

In particle physics, the major international laboratories are:

Many other particle accelerators exist.

The techniques required to do modern experimental particle physics are quite varied and complex, constituting a subspecialty nearly completely distinct from the theoretical side of the field. See Category:Experimental particle physics for a partial list of the ideas required for such experiments.

Theory

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. Theoretical physics employs Mathematical models and Abstractions of Physics in an attempt to explain experimental data taken of the natural world 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. There are five most important states in particle theory: one of the major activities in theoretical particle physics is the attempt to better understand the standard model and its tests. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles 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. Quantum chromodynamics (abbreviated as QCD is a theory of the Strong interaction ( color force a Fundamental force describing the interactions of the Some theorists making these efforts refer to themselves as phenomenologists and may use the tools of quantum field theory and effective field theory. Particle physics phenomenology is the part of theoretical Particle physics that deals with the application of theory to high energy particle physics experiments In quantum field theory (QFT the forces between particles are mediated by other particles In Physics, an effective field theory is an approximate theory (usually a Quantum field theory) that includes appropriate degrees of freedom to describe Others make use of lattice field theory and call themselves lattice theorists. In Physics, lattice field theory is the study of lattice models of Quantum field theory, that is of field theory on a spacetime that has been discretized

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). In Particle physics, the term model building refers to a construction of new quantum field theories beyond the Standard Model that have This work is often motivated by the hierarchy problem and is constrained by existing experimental data. In Theoretical physics, a hierarchy problem occurs when the fundamental parameters ( couplings or masses of some Lagrangian are vastly different (usually It may involve work on supersymmetry, alternatives to the Higgs mechanism, extra spatial dimensions (such as the Randall-Sundrum models), Preon theory, combinations of these, or other ideas. In Particle physics, supersymmetry (often abbreviated SUSY) is a Symmetry that relates elementary particles of one spin to another particle that The Higgs mechanism is Spontaneous symmetry breaking in a Gauge theory. In Physics, Randall-Sundrum models imagine that the real world is a higher-dimensional Universe described by Warped geometry. In Particle physics, preons are postulated "point-like" particles conceived to be subcomponents of Quarks and Leptons The word was coined

A third major effort in theoretical particle physics is string theory. String theory is a still-developing scientific approach to Theoretical physics, whose original building blocks are one-dimensional extended objects called strings 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. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 In Theoretical physics, a membrane, brane, or p -brane is a spatially extended mathematical concept that appears in String theory If the theory is successful, it may be considered a "Theory of Everything". A theory of everything ( TOE) is a putative Theory of Theoretical physics that fully explains and links together all known physical phenomena

There are also other areas of work in theoretical particle physics ranging from particle cosmology to loop quantum gravity. Loop quantum gravity (LQG, also known as loop gravity and Quantum geometry, is a proposed quantum theory of Spacetime which attempts to reconcile the theories

This division of efforts in particle physics is reflected in the names of categories on the preprint archive [2]: hep-th (theory), hep-ph (phenomenology), hep-ex (experiments), hep-lat (lattice gauge theory). The arXiv ( pronounced " Archive " as if the "X" were the Greek letter Chi, χ is an Archive for electronic In Physics, lattice gauge theory is the study of gauge theories on a spacetime that has been discretized onto a lattice.

Public Policy

Experimental results in particle physics are often obtained using enormous particle accelerators which are very expensive and require large amounts of government funding. Because of this, particle physics research involves issues of public policy.

The Future

Particle physicists internationally agree on the most important goals of particle physics research in the near and intermediate future. The overarching goal, which is pursued in several distinct ways, is to find and understand what physics may lie beyond the standard model. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles There are several powerful experimental reasons to expect new physics, including dark matter and neutrino mass. In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost There are also theoretical hints that this new physics should be found at accessible energy scales. Most importantly, though, there may be unexpected and unpredicted surprises which will give us the most opportunity to learn about nature.

Much of the efforts to find this new physics are focused on new collider experiments. A (relatively) near term goal is the completion of the Large Hadron Collider (LHC) in 2008 which will continue the search for the Higgs boson, supersymmetric particles, and other new physics. The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics In Particle physics, supersymmetry (often abbreviated SUSY) is a Symmetry that relates elementary particles of one spin to another particle that An intermediate goal is the construction of the International Linear Collider (ILC) which will complement the LHC by allowing more precise measurements of the properties of newly found particles. The International Linear Collider ( ILC) is a proposed Linear particle accelerator. A decision for the technology of the ILC has been taken in August 2004, but the site has still to be agreed upon.

Additionally, there are important non-collider experiments which also attempt to find and understand physics beyond the standard model. One important non-collider effort is the determination of the neutrino masses since these masses may arise from neutrinos mixing with very heavy particles. Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost In addition, cosmological observations provide many useful constraints on the dark matter, although it may be impossible to determine the exact nature of the dark matter without the colliders. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its Finally, lower bounds on the very long lifetime of the proton put constraints on Grand Unification Theories at energy scales much higher than collider experiments will be able to probe any time soon. In Particle physics, proton decay is a hypothetical form of Radioactive decay in which the Proton decays into lighter Subatomic particles Grand Unification, grand unified theory, or GUT refers to any of several very similar unified field theories or models in Physics that

See also

Notes

  1. ^ Review of particle physics. Atomic physics (or atom physics) is the field of Physics that studies atoms as an isolated system of Electrons and an atomic nucleus. In Physics, the Standard Model of Particle physics is currently the best description of all experimental data Quantum mechanics (QM or quantum theory) is a physical science dealing with the behavior of Matter and Energy on the scale of Atoms In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made A list of Particle accelerators used for Particle physics experiments For a basic description see the article on the Standard Model. A subatomic particle is an elementary or composite Particle smaller than an Atom. ICHEP or International Conference on High Energy Physics is the most prestigious international scientific conference in the field of Particle physics, bringing
  2. ^ Particle Physics News and Resources.
  3. ^ CERN Courier - International Journal of High-Energy Physics.
  4. ^ Particle physics in 60 seconds.

External links

The Particle Data Group is an international collaboration of particle Physicists that compiles and reanalyzes published results related to the properties of particles The Ernest Orlando Lawrence Berkeley National Laboratory ( LBNL) is a U Kuro5hin ( K5) ( pronounced " Corrosion " ie kəˈroʊʒən is a collaborative discussion website.
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