Physics
BaBar was set up to understand the disparity between the matter and antimatter content of the universe by measuring CP violation. CP symmetry is a combination of Charge-conjugation symmetry (C symmetry) and Parity symmetry (P symmetry), each of which are conserved separately except in weak interactions. BaBar focuses on the study of CP violation in the B meson system. The name of the experiment is derived from the nomenclature for the B meson (symbol B) and its antiparticle (symbol B, pronounced B bar). The experiment's mascot was accordingly chosen to be Babar the Elephant.
If CP symmetry holds, the decay rate of B mesons and their antiparticles should be equal. Analysis of secondary particles produced in the BaBar detector showed this was not the case – in the summer of 2002, definitive results were published based on the analysis of 87 million B/B meson-pair events, clearly showing the decay rates were not equal. Consistent results were found by the Belle experiment at the KEK laboratory in Japan.
CP violation was already predicted by the Standard Model of particle physics, and well established in the neutral kaon system (K/K meson pairs). The BaBar experiment has increased the accuracy to which this effect has been experimentally measured. Currently, results are consistent with the standard model, but further investigation of a greater variety of decay modes may reveal discrepancies in the future.
The BaBar detector is a multilayer particle detector. Its large solid angle coverage (near hermetic), vertex location with precision on the order of 10 μm (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 meson system. Studies of rare decays and searches for exotic particles and precision measurements of phenomena associated with mesons containing bottoms and charm quarks, as well as phenomena associated with tau leptons are possible.
The BaBar detector ceased operation on 7 April 2008, but data analysis is ongoing.
Read more about this topic: BaBar Experiment
Famous quotes containing the word physics:
“He who is conversant with the supernal powers will not worship these inferior deities of the wind, waves, tide, and sunshine. But we would not disparage the importance of such calculations as we have described. They are truths in physics because they are true in ethics.”
—Henry David Thoreau (1817–1862)
“The fundamental laws of physics do not describe true facts about reality. Rendered as descriptions of facts, they are false; amended to be true, they lose their explanatory force.”
—Nancy Cartwright (b. 1945)
“It is hardly to be believed how spiritual reflections when mixed with a little physics can hold people’s attention and give them a livelier idea of God than do the often ill-applied examples of his wrath.”
—G.C. (Georg Christoph)