BaBar-Experiment
BaBar is the name for an experiment of high energy physics.
It is built at the Stanford Linear Accelerator Center near Stanford University in California. A major goal of the experiment is to find evidence on the cause of the so-called CP violation, which the almost complete absence of antimatter in the universe is an essential prerequisite for the ( baryon asymmetry ). The observable CP violation, a violation of the symmetry of charge and parity is here investigated in the decay of B mesons and compared with the predictions of the Standard Model of particle physics. The CP violation is shown here in different behavior of B and anti-B mesons.
The BaBar collaboration consists of more than 600 physicists and engineers from 72 institutions in 12 countries. The experiment was named after " B and B - bar ", ie and, the latter stands for the anti-B and is referred to in English as the B- bar.
BaBar and the electron-positron storage ring PEP - II, including pre-accelerators provide a so-called B- factory represents the B- factory at SLAC has been launched as an initiative of U.S. President Bill Clinton in 1993. The data acquisition of the Babar experiment began in May 1999. Almost the same time with the competition experiment Belle at KEKB in Japan ( KEK ) has succeeded after a short start-up time in the summer of 2002, CP violation in the system of neutral mesons prove with a significance of more than 5σ. To date (August 2005) no contradiction to the predictions of the Standard Model has been found. CP violation was detected for the first (and BaBar only) time in the system of neutral kaons.
The BaBar detector is an ( almost) 4π particle detector with a typical shell structure. A Silicon Vertex Tracker inside ensures a vertex resolution of better than 60 microns. A multi-wire drift chamber reconstructed momentum of charged particles.
A special feature is an imaging Cherenkov detector with a novel design that requires very little material in the active region of the detector. Pions and kaons can be efficiently distinguished from each other in all pulse areas.
Further out reconstructs a CsI (Tl) calorimeter the energy of neutral particles.
Enclosed is the detector of muon chambers. Another feature of the B- factory is the asymmetric energy of the two - electron (9.0 GeV ) and positron radiation (3.1 GeV ) which are placed inside the detector for collision. The result is that the center of mass system moves relative to the detector. In this way the reconstruction of the different B- Zerfallsvertizes and thus the determination of the difference between the decay times of the pairs generated B mesons becomes possible, which is a prerequisite for the measurement of time-dependent imbalances in a CP- B- factory.
The data acquisition was extremely successful and was terminated in April 2008. PEP - II was able to supply an integrated luminosity of about 557 FB 1, wherein a maximum instantaneous luminosity of 1.2 x 1034cm - 2 s -1 was obtained. Relevant for B physics data taking was on the Υ ( 4S) resonance, in which an integrated luminosity of 424 fb- recorded one. To date (February 2013), the results of Datennalysen in more than 500 publications published in peer review journals. The analysis of BaBar data will be continued after the end of data taking. Thus succeeded in 2012, the direct detection of T- violation.