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Froissart Bound
In particle physics the Froissart bound, or Froissart limit, is a generic constraint that the total scattering cross section of two colliding high-energy particles cannot increase faster than c \ln^2(s) , with ''c'' a normalization constant and ''s'' the square of the center-of-mass energy (''s'' is one of the three Mandelstam variables In theoretical physics, the Mandelstam variables are numerical quantities that encode the energy, momentum, and angles of particles in a scattering process in a Lorentz-invariant fashion. They are used for scattering processes of two particles ...). Further readingThe Froissart bound on scholarpedia, by M. Froissart References Scattering theory {{Particle-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three generations of fermions, but ordinary matter is made only from the first fermion generation. The first generation consists of 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. Quarks cannot exist on their own but form hadrons. Hadrons that contain an odd number of quarks are called baryons and those that contain an even number are called mesons. Two baryons, the proton and the neutron, make up most of the mass of ordinary matter. Mesons are unstable and the longest-lived last for only a few hundredths of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattering Cross Section
In physics, the cross section is a measure of the probability that a specific process will take place when some kind of radiant excitation (e.g. a particle beam, sound wave, light, or an X-ray) intersects a localized phenomenon (e.g. a particle or density fluctuation). For example, the Rutherford cross-section is a measure of probability that an alpha particle will be deflected by a given angle during an interaction with an atomic nucleus. Cross section is typically denoted ( sigma) and is expressed in units of area, more specifically in barns. In a way, it can be thought of as the size of the object that the excitation must hit in order for the process to occur, but more exactly, it is a parameter of a stochastic process. In classical physics, this probability often converges to a deterministic proportion of excitation energy involved in the process, so that, for example, with light scattering off of a particle, the cross section specifies the amount of optical power scattered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandelstam Variables
In theoretical physics, the Mandelstam variables are numerical quantities that encode the energy, momentum, and angles of particles in a scattering process in a Lorentz-invariant fashion. They are used for scattering processes of two particles to two particles. The Mandelstam variables were first introduced by physicist Stanley Mandelstam in 1958. If the Minkowski metric is chosen to be \mathrm(1, -1,-1,-1), the Mandelstam variables s,t,u are then defined by :*s=(p_1+p_2)^2 c^2 =(p_3+p_4)^2 c^2 :*t=(p_1-p_3)^2 c^2 =(p_4-p_2)^2 c^2 :*u=(p_1-p_4)^2 c^2 =(p_3-p_2)^2 c^2, where ''p''1 and ''p''2 are the four-momenta of the incoming particles and ''p''3 and ''p''4 are the four-momenta of the outgoing particles. s is also known as the square of the center-of-mass energy ( invariant mass) and t as the square of the four-momentum transfer. Feynman diagrams The letters ''s,t,u'' are also used in the terms s-channel (timelike channel), t-channel, and u-channel (both spacelike channels) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
