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Resonance (particle Physics)
In particle physics, a resonance is the peak located around a certain energy found in differential cross sections of scattering experiments. These peaks are associated with subatomic particles, which include a variety of bosons, quarks and hadrons (such as nucleons, delta baryons or upsilon mesons) and their excitations. In common usage, "resonance" only describes particles with very short lifetimes, mostly high-energy hadrons existing for or less. It is also used to describe particles in intermediate steps of a decay, so-called virtual particles. The width of the resonance (''Γ'') is related to the mean lifetime (''τ'') of the particle (or its excited state) by the relation :\Gamma=\frac where =\frac and ''h'' is the Planck constant. Thus, the lifetime of a particle is the direct inverse of the particle's resonance width. For example, the charged pion has the second-longest lifetime of any meson, at . Therefore, its resonance width is very small, about or about 6.11 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combinations of protons and neutrons is called nuclear physics. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three Generation (particle physics), generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of Up quark, up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quark, Quarks cannot exist on their own but form hadrons. Hadrons that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pion
In particle physics, a pion (, ) or pi meson, denoted with the Greek alphabet, Greek letter pi (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 particle decay, decay into muons and muon neutrinos, while neutral pions generally decay into gamma rays. The exchange of virtual particle, virtual pions, along with vector meson, vector, rho meson, rho and omega mesons, provides an explanation for the nuclear force, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonances In Scattering From Potentials
In quantum mechanics, resonance cross section occurs in the context of quantum scattering theory, which deals with studying the scattering of quantum particles from potentials. The scattering problem deals with the calculation of flux distribution of scattered particles/waves as a function of the potential, and of the state (characterized by conservation of momentum/energy) of the incident particle. For a free quantum particle incident on the potential, the plane wave solution to the time-independent Schrödinger wave equation is: : \psi(\vec) = e^ For one-dimensional problems, the transmission coefficient T is of interest. It is defined as: :T = \frac where \vec J is the probability current density. This gives the fraction of incident beam of particles that makes it through the potential. For three-dimensional problems, one would calculate the scattering cross-section \sigma, which, roughly speaking, is the total area of the incident beam which is scattered. Another quantity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feshbach–Fano Partitioning
In quantum mechanics, and in particular in scattering theory, the Feshbach–Fano method, named after Herman Feshbach and Ugo Fano, separates (partitions) the resonant and the background components of the wave function and therefore of the associated quantities like cross sections or phase shift. This approach allows us to define rigorously the concept of resonance in quantum mechanics. In general, the partitioning formalism is based on the definition of two complementary projectors ''P'' and ''Q'' such that :''P'' + ''Q'' = 1. The subspaces onto which ''P'' and ''Q'' project are sets of states obeying the continuum and the bound state boundary conditions respectively. ''P'' and ''Q'' are interpreted as the projectors on the background and the resonant subspaces respectively. The projectors ''P'' and ''Q'' are not defined within the Feshbach–Fano method. This is its major power as well as its major weakness. On the one hand, this makes the method very general and, on the othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fano Resonance
In physics, a Fano resonance is a type of resonant scattering phenomenon that gives rise to an asymmetric line-shape. Interference between a background and a resonant scattering process produces the asymmetric line-shape. It is named after Italian-American physicist Ugo Fano, who in 1961 gave a theoretical explanation for the scattering line-shape of inelastic scattering of electrons from helium; however, Ettore Majorana was the first to discover this phenomenon. Fano resonance is a weak coupling effect meaning that the decay rate is so high, that no hybridization occurs. The coupling modifies the resonance properties such as spectral position and width and its line-shape takes on the distinctive asymmetric Fano profile. Because it is a general wave phenomenon, examples can be found across many areas of physics and engineering. History The explanation of the Fano line-shape first appeared in the context of inelastic electron scattering by helium and autoionization. The inciden ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feshbach Resonance
In physics, a Feshbach resonance can occur upon collision of two slow atoms when they temporarily stick together forming an unstable compound with short lifetime (so-called resonance). It is a feature of many-body systems in which a bound state is achieved if the coupling(s) between at least one internal degree of freedom and the reaction coordinates, which lead to dissociation, vanish. The opposite situation, when a bound state is not formed, is a shape resonance. It is named after Herman Feshbach, a physicist at MIT. Feshbach resonances have become important in the study of cold atoms systems, including Fermi gases and Bose–Einstein condensates (BECs). In the context of scattering processes in many-body systems, the Feshbach resonance occurs when the energy of a bound state of an interatomic potential is equal to the kinetic energy of a colliding pair of atoms. In experimental settings, the Feshbach resonances provide a way to vary interaction strength between a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Resonance
In nuclear physics, giant resonance is a high-frequency collective excitation of atomic nuclei, as a property of many-body quantum systems. In the macroscopic interpretation of such an excitation in terms of an oscillation, the most prominent giant resonance is a collective oscillation of all protons against all neutrons in a nucleus. In 1947, G. C. Baldwin and G. S. Klaiber observed the giant dipole resonance (GDR) in photonuclear reactions, and in 1972 the giant quadrupole resonance (GQR) was discovered, and in 1977 the giant monopole resonance (GMR) was discovered in medium and heavy nuclei.Chomaz, section 2.2.2.1 Giant dipole resonance Giant dipole resonances may result in a number of de-excitation events, such as nuclear fission, emission of neutrons or gamma rays, or combinations of these. Giant dipole resonances can be caused by any mechanism that imparts enough energy to the nucleus. Classical causes are irradiation with gamma rays at energies from 7 to 40 MeV, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roper Resonance
The Roper resonance, also known as P11(1440) or N(1440)1/2+, is an unstable nucleon resonance with a mass of about 1,440 MeV/c2 and with a relatively wide full Breit-Wigner width Γ ≈ 300 MeV/c2. It contains three quarks (up (u) or down (d)) with total spin ''J'' = 1/2 and total isospin ''I'' = 1/2. In the quark model it is considered to be a radially excited three-quark state with radial quantum number ''N'' = 2 and positive parity. The Roper Resonance has been a subject of many studies because its mass is actually lower than three-quark states with radial quantum number ''N'' = 1. Only in the late 2000s was the lower-than-expected mass explained by theoretical calculations, revealing a quark core shielded by a dense cloud of mesons. Discovery The Roper resonance was discovered in 1963 by a computer fit of particle-scattering theory to large amounts of pion-nucleon scattering data. The analysis was done on computers at Lawrence Livermore National Laboratory for Ph.D. thesis w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Baryons
Baryons are composite particles made of three quarks, as opposed to mesons, which are composite particles made of an equal number of quarks and antiquarks. Baryons and mesons are both hadrons, which are particles composed solely of quarks or both quarks and antiquarks. The term ''baryon'' is derived from the Greek ''"βαρύς"'' (''barys''), meaning "heavy", because, at the time of their naming, it was believed that baryons were characterized by having greater masses than other particles that were classed as matter. Pentaquarks are exotic baryons composed of four quarks and one antiquark. In 2015, the LHCb collaboration at CERN definitively reported the observation of pentaquark states in the decay of bottom lambda baryons (Λ).R. Aaij ''et al''. (2015) Since then, additional pentaquark states have been discovered, including new observations in 2019 and 2022. While primarily created in laboratory conditions, pentaquarks might also form naturally during neutron star formatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rest Mass
The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, it is a characteristic of the system's total energy and momentum that is the same in all frames of reference related by Lorentz transformations.Lawrence S. LernerPhysics for Scientists and Engineers, Volume 2, page 1073 1997. If a center-of-momentum frame exists for the system, then the invariant mass of a system is equal to its total mass in that "rest frame". In other reference frames, where the system's momentum is non-zero, the total mass (a.k.a. relativistic mass) of the system is greater than the invariant mass, but the invariant mass remains unchanged. Because of mass–energy equivalence, the rest energy of the system is simply the invariant mass times the speed of light squared. Similarly, the total energy of the system is its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zettahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base units is 1/s or s−1, meaning that one hertz is one per second or the reciprocal of one second. It is used only in the case of periodic events. It is named after Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. For high frequencies, the unit is commonly expressed in multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation of the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megaelectronvolt
In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum. When used as a unit of energy, the numerical value of 1 eV in joules (symbol J) is equal to the numerical value of the charge of an electron in coulombs (symbol C). Under the 2019 revision of the SI, this sets 1 eV equal to the exact value Historically, the electronvolt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because a particle with electric charge ''q'' gains an energy after passing through a voltage of ''V''. Definition and use An electronvolt is the amount of energy gained or lost by a single electron when it moves through an electric potential difference of one volt. Hence, it has a value of one volt, which is , multiplied by the elementary charge There ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
