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Encyclopedia > BaBar Experiment

The BaBar (B and B-bar) experiment is an international collaboration of more than 550 physicists and engineers investigating CP-violation effects using the BaBar particle detector at the Stanford Linear Accelerator Center, which is operated by Stanford University in California. CP-symmetry is a symmetry obtained by a combination of the C-symmetry and the P-symmetry. ... The Stanford Linear Accelerator Center (SLAC) is a U.S. national laboratory operated by Stanford University for the U.S. Department of Energy. ... Stanford redirects here. ... This article is becoming very long. ...


BaBar was set up to study the difference between matter and antimatter — CP-violation. CP is the product of the Charge and Parity symmetries. In classical physics both symmetries are conserved, but this is not the case at sub-atomic scales. In particle physics, antimatter extends the concept of the antiparticle to matter, wherein if a particle and its antiparticle come into contact with each other, the two annihilate —that is, they may both be converted into other particles with equal energy in accordance with Einsteins equation E = mc2. ... Classical physics is physics based on principles developed before the rise of quantum theory, usually including the special theory of relativity and general theory of relativity. ...


If the CP symmetry holds, the decay rate of B meson particles and their anti-particles should be equal. Analysis of the BaBar results showed this was not the case — in the summer of 2002, definitive results were published based on the analysis of 87 million B/B-bar meson-pair events, clearly showing the decay rates were not equal. Consistent results were also gathered in the Belle experiment at the KEK laboratory in Japan. In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... Corresponding to each kind of particle, there is an associated antiparticle with the same mass and opposite charges. ... In the field of particle physics Belle Experiment is an international collaboration of more than 400 physicists and engineers investigating CP-violation effects using the Belle particle detector at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan. ... KEK is the High Energy Accelerator Research Organisation in Tsukuba, Ibaraki Prefecture, Japan. ...


CP-violation was already predicted by the Standard Model of physics but the BaBar detector has increased the accuracy to which this effect has been experimentally measured. Currently results are in agreement with the standard model, but further investigation of a greater variety of decay modes may reveal discrepancies in the future. The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...


The BaBar detector is a multi-layer particle detector. Its large solid angle coverage (near hermetic), vertex location with precision on the order of tens of micrometres (provided by a silicon vertex detector), good pion-kaon separation at multi-GeV momenta (provided by a novel Cherenkov detector), and few-percent precision electromagnetic calorimetry (CsI(Tl) scintillating crystals) allow a list of other scientific searches apart from CP violation in the B system.[1] Studies of rare decays and searches for exotic particles and precision measurements of bottom and charm mesons and tau leptons are possible. A currently-operating hermetic detector, the Collider Detector at Fermilab. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: π0, π+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... In particle physics, Kaons (also called K-mesons and denoted K) are a group of four mesons distinguished by the fact that they carry a quantum number called strangeness. ... A GEV (or Ground Effect Vehicle) is vehicle that takes advantage of the aerodynamic principle of ground effect (or Wing-in-ground). ... Cherenkov effect at the UMRs nuclear reactor Cherenkov radiation (also spelled Cerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than that of light in the medium. ... The tau lepton (often called the tau or occasionally the tauon) is a negatively charged elementary particle with a lifetime of 3×10−13 seconds and a high mass of 1777 MeV (compared to 939 MeV for protons and 0. ...


Experiment is named after the B and B-bar (anti-B) particles it is investigating and the name is a reference to Babar the Elephant which has been chosen as the mascot. Cover of the first Babar story published 1931 Cover of the second Babar story published 1932 Babar the Elephant is a popular French childrens fictional character who first appeared in LHistoire de Babar by Jean de Brunhoff in 1931 and enjoyed immediate success. ... Mascots at the Mascot Olympics in Orlando, Florida. ...


Notable Events

On 9 October 2005, BaBar recorded a record luminosity just over 1x1034 cm-2s-1 delivered by the PEP-II positron-electron collider.[2] This represents 330% of the luminosity that PEP-II was designed to deliver, and was produced along with a world record for stored current in an electron storage ring at 1732 mA, paired with a record 2940 mA of positrons. "For the BaBar experiment, higher luminosity means generating more collisions per second, which translates into more accurate results and the ability to find physics effects they otherwise couldn’t see."[3] Luminosity has different meanings in several different fields of science. ... A 1960s single stage 2 MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric fields to propel electrically charged particles to high speeds and magnetic fields to contain them. ... The Electron is a fundamental subatomic particle that carries an electric charge. ... A small storage ring at SLAC. This particlular storage ring is one of the two small storage rings or circular cyclotron. ... In physics, the ampere (symbol: A, often informally abbreviated to amp) is the SI base unit used to measure electrical currents. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ...


During down time in 2004 and 2006, BaBar replaced ailing Resistive Plate Chambers with Limited Streamer Tubes for muon and KL detection.


External links

Sources

  1.   BaBar Collaboration, B. Aubert. et al., Nucl. Instrum. Methods A 479, 1 (2002).
  2.  Daily PEP-II-delivered and BaBar-recorded luminosities. (bar chart) Accessed 11 October 2005.
  3.  Dynamic Performance from SLAC B-Factory. Accessed 11 October 2005.

  Results from FactBites:
 
BaBar Experiment - definition of BaBar Experiment in Encyclopedia (183 words)
In the field of particle physics BaBar is an international collaboration at the Stanford Linear Accelerator investigating CP-violation effects using the BaBar particle detector.
Analysis of the BaBar results showed this was not the case - in the summer of 2002, definitive results were published based on the analysis of 87 million B/B-bar meson-pair events, clearly showing the decay rates were not equal.
CP-violation was already predicted by the Standard Model of physics but the BaBar detector has increased the accuracy to which this effect has been experimentally measured.
BaBar experiment - Wikipedia, the free encyclopedia (307 words)
In the field of particle physics BaBar is an international collaboration of more than 550 physicists and engineers investigating CP-violation effects using the BaBar particle detector at the Stanford Linear Accelerator, Stanford, CA, USA.
Analysis of the BaBar results showed this was not the case—in the summer of 2002, definitive results were published based on the analysis of 87 million B/B-bar meson-pair events, clearly showing the decay rates were not equal.
Consistent results were also gathered in the Belle experiment at the KEK laboratory in Japan.
  More results at FactBites »

 
 

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