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Bhabha Scattering
In quantum electrodynamics, Bhabha scattering is the electron-positron scattering process: ::e^+ e^- \rightarrow e^+ e^- There are two leading-order Feynman diagrams contributing to this interaction: an annihilation process and a scattering process. Bhabha scattering is named after the Indian physicist Homi J. Bhabha. The Bhabha scattering rate is used as a luminosity monitor in electron-positron colliders. Due to crossing symmetry, Bhabha scattering has the same amplitude as Møller scattering. Differential cross section To leading order, the spin-averaged differential cross section for this process is ::\frac = \frac \left( u^2 \left( \frac + \frac \right)^2 + \left( \frac \right)^2 + \left( \frac \right)^2 \right) \, where ''s'',''t'', and ''u'' are the Mandelstam variables, \alpha is the fine-structure constant, and \theta is the scattering angle. This cross section is calculated neglecting the electron mass relative to the collision energy and including only the contri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feynman Diagrams
In theoretical physics, a Feynman diagram is a pictorial representation of the mathematical expressions describing the behavior and interaction of subatomic particles. The scheme is named after American physicist Richard Feynman, who introduced the diagrams in 1948. The calculation of probability amplitudes in theoretical particle physics requires the use of large, complicated integrals over a large number of variable (mathematics), variables. Feynman diagrams instead represent these integrals graphically. Feynman diagrams give a simple visualization of what would otherwise be an arcane and abstract formula. According to David Kaiser (physicist), David Kaiser, "Since the middle of the 20th century, theoretical physicists have increasingly turned to this tool to help them undertake critical calculations. Feynman diagrams have revolutionized nearly every aspect of theoretical physics." While the diagrams apply primarily to quantum field theory, they can be used in other areas o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belle Experiment
The Belle experiment was a particle physics experiment conducted by the Belle Collaboration, an international collaboration of more than 400 physicists and engineers, at the High Energy Accelerator Research Organisation ( KEK) in Tsukuba, Ibaraki Prefecture, Japan. The experiment ran from 1999 to 2010. The Belle detector was located at the collision point of the asymmetric-energy electron–positron collider, KEKB. Belle at KEKB together with the BaBar experiment at the PEP-II accelerator at SLAC were known as the B-factories as they collided electrons with positrons at the center-of-momentum energy equal to the mass of the (4S) resonance which decays to pairs of B mesons. The Belle detector was a hermetic multilayer particle detector with large solid angle coverage, vertex location with precision on the order of tens of micrometres (provided by a silicon vertex detector), good distinction between pions and kaons in the momenta range from 100 MeV/c to few GeV/c (provi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beijing Electron–Positron Collider II
The Beijing Electron–Positron Collider II (BEPC II) is a Chinese electron–positron collider, a type of particle accelerator, located in Shijingshan District, Beijing, People's Republic of China. It has been in operation since 2008 and has a circumference of 240.4 m. It was intended as a charm factory and continues the role of CLEO-c detector. The center of mass energy can go up to 4.6 GeV with a design luminosity of 1033 cm−2·s−1. Operations began in summer 2008 and the machine has run at multiple energies. History The construction of the original Beijing Electron Positron Collider was approved in 1983, as China was emerging from the Cultural Revolution, based on a proposal developed by Xie Jialin, who went on to oversee the construction of the machine. The construction of this collider was considered so important that then vice-premier Deng Xiaoping attended the groundbreaking in 1984 and returned in 1988 as the machine neared operation. The ori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stanford Large Detector
SLAC National Accelerator Laboratory, originally named the Stanford Linear Accelerator Center, is a federally funded research and development center in Menlo Park, California, United States. Founded in 1962, the laboratory is now sponsored by the United States Department of Energy and administrated by Stanford University. It is the site of the Stanford Linear Accelerator, a 3.2 kilometer (2-mile) linear accelerator constructed in 1966 that could accelerate electrons to energies of 50 GeV. Today SLAC research centers on a broad program in atomic and solid-state physics, chemistry, biology, and medicine using X-rays from synchrotron radiation and a free-electron laser as well as experimental and theoretical research in elementary particle physics, accelerator physics, astroparticle physics, and cosmology. The laboratory is under the programmatic direction of the United States Department of Energy Office of Science. History Founded in 1962 as the Stanford Linear Accelerator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
