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Development of the babar detector at the pep-ii-b-factory for the experimental study of cp violation in b meson decays


Research objectives and content
Since 1964, the CP symmetry has been known to be violated in neutral K meson decays. This very small effect, which could be linked to the observed dominance of matter over antimatter in the Universe, can be accommodated in the Standard Model of electroweak and strong interactions with three fermion generations. Such a scheme predicts sizeable CP violating asymmetries in few rare decays of mesons containing b quarks. Two B meson factories and their associated experiments are under construction in order to measure the time dependence of the CP asymmetry. One of them, the BABAR collaboration, involves many European laboratories and Universities. The project will be developed in this environment. The tagging of the few and rare Br decay channels sensitive to CP violation requires a novel type of ring image Cherenkov detector, the DIRC (Detector of Internally Refiected Cherenkov light). The DIRC construction has been shared between French and American institutes (SLAC and Berkeley). The LPNHE has responsibilities on the front-end electronics, the calibration system and online (monitoring) and offline (pattern recognition) reconstruction programs. More global tasks taken up by the group are overall particle identification (using all subdetectors) and flavour tagging.Technical and physics activities will span the whole term of the grant. Due to the time schedule of the experiment, the emphasis will be put on the techical part at the beginning and on physics later on. The main technical points of the research project are the following: a) take part in the installation of the detector, in particular the DIRC; b) participate in the DIRC and. BABAR check out with cosmic rays and calibration; and c) become involved in online/offline object oriented C++ programming of the DIRC. Software tools for physics analyses will be in full development in 1998 and 1999. Contribution to the advance of flavour tagging techniques and methods to analyze the data arriving in 1999 will be an important part of the project.
Training content (objective, benefit and expected impact
On the technical side, to learn more about detector control, calibration and monitoring of a big detector. To develop software (online/offline) with object oriented programming C++, which means a significant change of methodology in HEP. On the physics side, CP violation precision analyses will allow a better knowledge of acute HEP and cosmological problems. A I very important benefit of the candidate will be the strong feed-back and environment of many physicists inside a world wide experiment. After two years of grant, it will be too early to have very accurate results on CP violation. But I hope to have enough experience at this time to l join other physicists in order to form a nucleus in Spain on this topic to go ahead with the work.
l Links with industry / industrial relevance (22)


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