|
XYZ Particle
XYZ particles, also referred to as XYZ states, are recently discovered heavy mesons whose properties do not appear to fit the standard picture of charmonium and bottomonium states. They are therefore types of exotic meson. The term arises from the names given to some of the first such particles discovered: X(3872), Y(4260) and Zc(3900), although the symbols X and Y have since been deprecated by the Particle Data Group. Theoretical significance Since 2003 a frontier for the Standard Model (SM) has emerged at low energies through XYZ particle discoveries. The well-established theory of Quantum Chromodynamics (QCD) is tested by many exotic charmonium discoveries since the X(3872) was first identified at the Belle experiment in 2003. The basic model of hadron physics is the assembling of quarks into groups of 3 (baryons) or a quark and anti-quark pair (mesons). A meson with a charm quark and an anti-charm quark is called ''charmonium'', and the same parallels with the bottom quark a ... [...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] |
Gluon
A gluon ( ) is an elementary particle that acts as the exchange particle (or gauge boson) for the strong force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles. Gluons bind quarks together, forming hadrons such as protons and neutrons. Gluons are vector gauge bosons that mediate strong interactions of quarks in quantum chromodynamics (QCD). Gluons themselves carry the color charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction but lacks an electric charge. Gluons therefore participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than quantum electrodynamics (QED). Properties The gluon is a vector boson, which means, like the photon, it has a spin of 1. While massive spin-1 particles have three polarization states, massless gauge bosons like the gluon have only two polarization states because gauge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initial And Final State Radiation
In quantum field theory, initial and final state radiation refers to certain kinds of radiative emissions that are not due to particle annihilation. Kim Alwyn. Accessed 08 March 2013. It is important in experimental and theoretical studies of interactions at particle colliders. Explanation of initial and final states Particle accelerators and colliders produce collisions (interactions) of particles (like the or the ). In th ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BES III
The Beijing Spectrometer III (BES III) is a particle physics experiment at the Beijing Electron–Positron Collider II (BEPC II) at the Institute of High Energy Physics (IHEP). It is designed to study the physics of charm, charmonium, and light hadron decays. It also performs studies of the tau lepton, tests of QCD, and searches for physics beyond the Standard Model. The experiment started collecting data in the summer of 2008. Beam BES III receives electron–positron collisions from BEPC II: a circular collider with a circumference of 240 m. BEPC II maintains a variable collision energy between 2 and 4.63 GeV, with a luminosity of 1033 cm−2·s−1. Each of the beams contains 93 electron or positron bunches of length 1.5 cm and a total current of 0.91 A. Detector The BES III detector is a cylindrically symmetric 6-meter long and 7-meter diameter detector surrounding the interaction point of 2 beam pipe rings. It has 4 major detector layers: a main drift chamber (MD ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Π Meson
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 process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initial State Radiation
In quantum field theory, initial and final state radiation refers to certain kinds of radiative emissions that are not due to particle annihilation. Kim Alwyn. Accessed 08 March 2013. It is important in experimental and theoretical studies of interactions at particle colliders. Explanation of initial and final states Particle accelerators and colliders produce collisions (interactions) of particles (like the or the ). In th ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
D Meson
The D mesons are the lightest particle containing charm quarks. They are often studied to gain knowledge on the weak interaction. The strange D mesons (Ds) were called "F mesons" prior to 1986. Overview The D mesons were discovered in 1976 by the Mark I detector at the Stanford Linear Accelerator Center. Since the D mesons are the lightest mesons containing a single charm quark (or antiquark), they must change the charm (anti)quark into an (anti)quark of another type to decay. Such transitions involve a change of the internal charm quantum number, and can take place only via the weak interaction. In D mesons, the charm quark preferentially changes into a strange quark via an exchange of a W particle, therefore the D meson preferentially decays into kaons () and pions (). List of D mesons ‡ PDG reports the resonance width ~\left(\Gamma\right)~. Here the conversion \; \tau = \frac \; is given instead. – oscillations In 2021 it was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DØ Experiment
The DØ experiment (sometimes written D0 experiment, or DZero experiment) was a worldwide collaboration of scientists conducting research on the fundamental nature of matter. DØ was one of two major experiments (the other was the CDF experiment) located at the Tevatron Collider at Fermilab in Batavia, Illinois. The Tevatron was the world's highest-energy accelerator from 1983 until 2009, when its energy was surpassed by the Large Hadron Collider. The DØ experiment stopped taking data in 2011, when the Tevatron shut down, but data analysis is still ongoing. The DØ detector is preserved in Fermilab's DØ Assembly Building as part of a historical exhibit for public tours. DØ research is focused on precise studies of interactions of protons and antiprotons at the highest available energies. These collisions result in "events" containing many new particles created through the transformation of energy into mass according to the relation E=mc2. The research involves an inten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collider Detector At Fermilab
The Collider Detector at Fermilab (CDF) experimental collaboration studies high energy particle collisions from the Tevatron, the world's former highest-energy particle accelerator. The goal is to discover the identity and properties of the particles that make up the universe and to understand the forces and interactions between those particles. CDF is an international collaboration that, at its peak, consisted of about 600 physicists (from about 30 American universities and National laboratories and about 30 groups from universities and national laboratories from Italy, Japan, UK, Canada, Germany, Spain, Russia, Finland, France, Taiwan, Korea, and Switzerland). The CDF detector itself weighed about 5000 tons and was about 12 meters in all three dimensions. The goal of the experiment is to measure exceptional event (particle physics), events out of the billions of particle Beam crossing, collisions in order to: * Look for evidence for phenomena beyond the Standard Model of particl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BaBar
Babar ( ur, ), also variously spelled as Baber, Babur, and Babor is a male given name of Pashto, and Persian language, Persian origin, and a popular male given name in Pakistan. It is generally taken in reference to the Persian language, Persian ''babr'' (Persian language, Persian: ببر), meaning "tiger". There is a similar name in connotation to the Arabic male given form and generic name of the animal by the name "Nimr (other), Nimr" (Arabic: نَمِر ''namir'') which means "yellow-black stripped cat", i.e. "tiger". The word repeatedly appears in Ferdowsi's ''Shahnameh'' and was borrowed into the Turkic languages of Central Asia.Thumb, Albert, ''Handbuch des Sanskrit, mit Texten und Glossar'', German original, ed. C. Winter, 1953Snippet, p. 318/ref> Wheeler Thackston, Thackston argues for an alternate derivation from the Proto-Indo-European language, PIE word "beaver", pointing to similarities between the pronunciation ''Bābor'' and the Russian ''bobr'' (, "beaver" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Numbers
In quantum physics and chemistry, quantum numbers describe values of conserved quantities in the dynamics of a quantum system. Quantum numbers correspond to eigenvalues of operators that commute with the Hamiltonian—quantities that can be known with precision at the same time as the system's energyspecifically, observables \widehat that commute with the Hamiltonian are simultaneously diagonalizable with it and so the eigenvalues a and the energy (eigenvalues of the Hamiltonian) are not limited by an uncertainty relation arising from non-commutativity.—and their corresponding eigenspaces. Together, a specification of all of the quantum numbers of a quantum system fully characterize a basis state of the system, and can in principle be measured together. An important aspect of quantum mechanics is the quantization of many observable quantities of interest.Many observables have discrete spectra (sets of eigenvalues) in quantum mechanics, so the quantities can only be measure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
