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Pionium
Pionium is a composite particle consisting of one and one meson. It can be created, for instance, by interaction of a proton beam accelerated by a particle accelerator and a target nucleus. Pionium has a short lifetime, predicted by chiral perturbation theory to be . It decays mainly into two mesons, and to a smaller extent into two photons. It has been investigated at CERN to measure its lifetime. The Dimeson Relativistic Atomic Complex (DIRAC) experiment at the Proton Synchrotron was able to detect 21227 atomic pairs from a total of events, which allows the pionium lifetime to be determined to within statistical errors of 9%. In 2006, the NA48/2 collaboration at CERN published an evidence for pionium production and decay in decays of charged kaons, studying mass spectra of daughter pion pairs in the events with three pions in the final state K± → π±(ππ)atom → π±π0π0. This was followed by a precision measurement of the S-wave pion scattering ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesonic Molecule
A mesonic molecule is a set of two or more mesons bound together by the strong force. Unlike baryonic molecules, which form the nuclei of all elements in nature save hydrogen-1, a mesonic molecule has yet to be definitively observed. The X(3872) discovered in 2003 and the Z(4430) discovered in 2007 by the Belle experiment are the best candidates for such an observation. See also *Meson *Tetraquark A tetraquark, in particle physics, is an exotic meson composed of four valence quarks. A tetraquark state has long been suspected to be allowed by quantum chromodynamics, the modern theory of strong interactions. A tetraquark state is an example ... * Pionium References Hypothetical composite particles {{Particle-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onium
An onium (plural: onia) is a bound state of a particle and its antiparticle. These states are usually named by adding the suffix ''-onium'' to the name of one of the constituent particles (replacing an ''-on'' suffix when present), with one exception for "muonium"; a muon–antimuon bound pair is called "true muonium" to avoid confusion with old nomenclature. Examples Positronium is an onium which consists of an electron and a positron bound together as a long-lived metastable state. Positronium has been studied since the 1950s to understand bound states in quantum field theory. A recent development called non-relativistic quantum electrodynamics (NRQED) used this system as a proving ground. Pionium, a bound state of two oppositely-charged pions, is interesting for exploring the strong interaction. This should also be true of protonium. The true analogs of positronium in the theory of strong interactions are the quarkonium states: they are mesons made of a heavy quark and antiqua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pion
In particle physics, a pion (or a pi meson, denoted with the Greek letter pi: ) is any of three subatomic particles: , , and . Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the lightest mesons and, more generally, the lightest hadrons. They are unstable, with the charged pions and decaying after a mean lifetime of 26.033 nanoseconds ( seconds), and the neutral pion decaying after a much shorter lifetime of 85 attoseconds ( seconds). Charged pions most often decay into muons and muon neutrinos, while neutral pions generally decay into gamma rays. The exchange of virtual pions, along with vector, rho and omega mesons, provides an explanation for the residual strong force between nucleons. Pions are not produced in radioactive decay, but commonly are in high-energy collisions between hadrons. Pions also result from some matter–antimatter annihilation events. All types of pions are also produced in natural processes wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Composite Particle
This is a list of known and hypothesized particles. Elementary particles Elementary particles are particles with no measurable internal structure; that is, it is unknown whether they are composed of other particles. They are the fundamental objects of quantum field theory. Many families and sub-families of elementary particles exist. Elementary particles are classified according to their spin. Fermions have half-integer spin while bosons have integer spin. All the particles of the Standard Model have been experimentally observed, including the Higgs boson in 2012. Many other hypothetical elementary particles, such as the graviton, have been proposed, but not observed experimentally. Fermions Fermions are one of the two fundamental classes of particles, the other being bosons. Fermion particles are described by Fermi–Dirac statistics and have quantum numbers described by the Pauli exclusion principle. They include the quarks and leptons, as well as any composite particles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NA48 Experiment
The NA48 experiment was a series of particle physics experiments in the field of kaon physics being carried out at the North Area of the Super Proton Synchrotron at CERN. The collaboration involved over 100 physicists mostly from Western Europe and Russia. The construction of the NA48 experimental setup took place early 1990s. The primary physics goal – the search for direct CP violation – was inherited from the predecessor NA31 experiment. The physics data taking runs took place between 1997 and 2001. The discovery of the phenomenon of direct CP violation, one of the most important experimental results obtained at CERN, was announced by the collaboration in 1999. The publication of the final result was made in 2001. In addition the experiment made a contribution to studies of rare decays of neutral kaons. The following stage of the experiment (NA48/1) was carried out in 2002 and was devoted to high precision study of rare decays of neutral kaons and hyperons. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Physics B
The ''Journal of Physics B: Atomic, Molecular and Optical Physics'' is a biweekly peer-reviewed scientific journal published by IOP Publishing. It was established in 1968 from the division of the earlier title, ''Proceedings of the Physical Society''. In 2006, the '' Journal of Optics B: Quantum and Semiclassical Optics'' was merged with the ''Journal of Physics B''. The editor-in-chief is Marc Vrakking (Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy). Scope The journal covers research on atomic, molecular, and optical physics. Topics include atomic and molecular structure, spectra and collisions, ultracold matter, quantum optics and non linear optics, quantum information, laser physics, intense laser fields, ultrafast and x-ray physics and atomic and molecular physics in plasmas. The journal publishes research papers, fast track communications, topical reviews, tutorials, and invited articles. It occasionally publishes special issues on developing resea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Chromodynamics
In theoretical physics, quantum chromodynamics (QCD) is the theory of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a type of quantum field theory called a non-abelian gauge theory, with symmetry group SU(3). The QCD analog of electric charge is a property called ''color''. Gluons are the force carriers of the theory, just as photons are for the electromagnetic force in quantum electrodynamics. The theory is an important part of the Standard Model of particle physics. A large body of experimental evidence for QCD has been gathered over the years. QCD exhibits three salient properties: * Color confinement. Due to the force between two color charges remaining constant as they are separated, the energy grows until a quark–antiquark pair is spontaneously produced, turning the initial hadron into a pair of hadrons instead of isolating a color charge. Although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Physical Journal C
The ''European Physical Journal C'' (''EPJ C'') is a biweekly peer-reviewed, open access scientific journal covering theoretical and experimental physics. It is part of the SCOAP3 initiative. See also * ''European Physical Journal The ''European Physical Journal'' (or ''EPJ'') is a joint publication of EDP Sciences, Springer Science+Business Media, and the Società Italiana di Fisica. It arose in 1998 as a merger and continuation of ''Acta Physica Hungarica'', '' Anales d ...'' References Physics journals Springer Science+Business Media academic journals Publications established in 1998 English-language journals Semi-monthly journals EDP Sciences academic journals Particle physics journals {{physics-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattering Length
The scattering length in quantum mechanics describes low-energy scattering. For potentials that decay faster than 1/r^3 as r\to \infty, it is defined as the following low-energy limit: : \lim_ k\cot\delta(k) =- \frac\;, where a is the scattering length, k is the wave number, and \delta(k) is the phase shift of the outgoing spherical wave. The elastic cross section, \sigma_e, at low energies is determined solely by the scattering length: : \lim_ \sigma_e = 4\pi a^2\;. General concept When a slow particle scatters off a short ranged scatterer (e.g. an impurity in a solid or a heavy particle) it cannot resolve the structure of the object since its de Broglie wavelength is very long. The idea is that then it should not be important what precise potential V(r) one scatters off, but only how the potential looks at long length scales. The formal way to solve this problem is to do a partial wave expansion (somewhat analogous to the multipole expansion in classical electrodynamic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kaon
KAON (Karlsruhe ontology) is an ontology infrastructure developed by the University of Karlsruhe and the Research Center for Information Technologies in Karlsruhe. Its first incarnation was developed in 2002 and supported an enhanced version of RDF ontologies. Several tools like the graphical ontology editor OIModeler or the KAON Server were based on KAON. There are ontology learning companion tools which take non-annotated natural language text as input: TextToOnto (KAON-based) and Text2Onto (KAON2-based). Text2Onto is based on the Probabilistic Ontology Model (POM). In 2005, the first version of KAON2 was released, offering fast reasoning support for OWL ontologies. KAON2 is not backward-compatible with KAON. KAON2 is developed as a joint effort of the Information Process Engineering (IPE) at the Research Center for Information Technologies (FZI), the Institute of Applied Informatics and Formal Description Methods (AIFB) at the University of Karlsruhe, and the Information Ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics Letters B
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, with its main goal being to understand how the universe behaves. "Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, they have a meaningful physical size, a diameter of roughly one femtometre (10 m), which is about 0.6 times the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Heavier mesons decay to lighter mesons and ultimately to stable electrons, neutrinos and photons. Outside the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays (high-energy protons and neutrons) and baryonic matter. Mesons are routinely produced artificially in cyclotrons or other particle accelerators in the collisions of protons, antiprotons, or other particles. Higher-energy (more massive) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
