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BaBar Group

The BaBar Detector The PEP-II Collider

The Experiment

The universe is composed mostly of matter particles such as protons, neutrons and electrons rather than their antimatter partners; antiprotons, antineutrons and positrons. During its creation, matter and antimatter were produced in equal amounts, and the prevailing dominance of one over the other is thought to have been triggered by some phenomenon at a later stage of the universe's evolution. The BaBar experiment at SLAC is built to study that phenomenon called CP violation in the decays of B mesons, which are produced by the PEP-II e+e- collider. The main aim of the experiment is to look for differences in the decays of B mesons compared to their antimatter partner, the B-bar mesons, in the hope of understanding better the prevailing matter-antimatter asymmetry in the universe.

BaBar recorded its first e+e- collision data in May 1999 and stopped taking data on April 2008, accumulating nearly 500 million BB-bar events. The performance of the PEP-II collider has been excellent, reaching the design luminosity during its first year of operation and exceeding design by more than a factor of three. On the detector side, BaBar presented its first physics results at the Osaka conference in July 2000, just one year after the start of the data taking! It published the most awaited result: the first definitive observation of CP violation in B meson decays in July 2001 and although active data-taking phase is now over, it still continues to exploit its excellent physics capability, having published more than 300 physics papers to date.

The University of Warwick was vigorously active on the BaBar experiment from 2004 until 2008. The main focus of our efforts was on analysing the experimental data and producing physics results. We contributed significantly to the analysis of B decays to hadronic final states without a charm quark. We were also involved in software development for the BaBar Calorimeter, particularly on distinguishing charged vs. neutral particle passing through it. The main focus of our B physics activity moved to LHCb in 2009, but we continue to contribute to BaBar publication. Please contact Dr. Tim Gershon for more information.