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The Universe exhibits a remarkable asymmetry without which we could not exist: it contains large quantities of matter but almost no antimatter. Yet in the interactions of elementary particles at high energy as much antimatter as matter is produced. While it is clear that this asymmetry occurred in the very early evolution of the Universe the mechanism is not understood. However one key element is the phenomenon of CP violation, which results in a small difference in the way in which particles and their antiparticles decay. CP violation was discovered in 1963 in the decays of K mesons and has been investigated in detail since then in these decays. During the 1990s new projects were developed to extend these measurements to the decay of B mesons. Two major projects, Belle at KEK in Japan and BABAR at SLAC in the USA, began operation in 1999 and reported first results in 2000. This paper reviews the phenomenon of CP Violation in the decays of elementary particles and demonstrates the basis for the measurements of CP violation parameters in B meson decays. A description is given of the BABAR detector together with an outline of the procedure for analysing the data. First results are consistent with predictions of the Standard Model of elementary particles but during the coming years additional data will provide more stringent tests that could reveal new phenomena.

The BABAR detector at PEP-II will operate in a high-luminosity [e.sup.+][e.sup.-] collider environment near the [Gamma](4S) resonance with the primary goal of studying CP violation in the B meson system. In this environment, typical physics events of interest involve multiple charged particles. These events are identified by counting these tracks in a fast first level (Level 1) trigger system, by reconstructing the tracks in 'real time.' For this purpose, a Binary Link Tracker Module (BLTM) was designed and fabricated for the BABAR Level 1 Drift Chamber trigger system. The BLTM is responsible for linking track segments, constructed by the Track Segment Finder Modules (TSFM), into complete tracks. A single BLTM module processes a 360 MBytes/s stream of segment hit data, corresponding to information from the entire Drift Chamber, and implements a fast and robust algorithm that tolerates high hit occupancies as well as local inefficiencies of the Drift Chamber. The algorithms and the necessary control logic of the BLTM were implemented in Field Programmable Gate Arrays (FPGAs), using the VHDL hardware description language. The finished 9U x 400 mm Euro-format board contains roughly 75,000 gates of programmable logic or about 10,000 lines of VHDL code synthesized into five FPGAs.

The CP violation experiment HERA-B at DESY [1] requires a highly selective on-line filtering of data due to high interaction rates and low signal to background ratio. This demands a hierarchical trigger system and a data acquisition with high bandwidth. A complete level of the trigger hierarchy and the DAQ chain can be built from a single unit type: a single slot 6U VME unit carrying six ADSP21060 (SHARC) DSPs [2]. The six SHARCs communicate via the common bus or via their link ports, which are all accessible from the front panel. Up to 350 units will be used in the experiment. Prototype units have been built and are operating successfully.

A 24 x 24 [cm.sup.2] asymmetric multiwire proportional chamber, with 7.5 x 7.5 [mm.sup.2] photosensitive CsI pads, has been tested with Cherenkov radiation of 3 GeV/c electrons in the T24 test beam at DESY. The performance of the chamber with specially designed low-noise, charge-sensitive preamplifiers is described. The parameters of the CsI-MWPC are compared to those of a TMAE photon detector in order to evaluate their potential as Ring Imaging Cherenkov (RICH) counters for the HERA-B experiment at DESY.

After some general remarks about 'big bang' cosmology it is pointed out how, in order to explain why there is matter but no antimatter in the observed Universe, reactions involving violation of baryon number must have taken place at early times. It turns out that processes violating time reversal invariance are also necessary. The article surveys the subjects of the discrete symmetries (space inversion, time reversal and particle - antiparticle transformation) and their violation in elementary-particle physics, and grand unified theories, which predict baryon number violation. A simple model is then presented which could account qualitatively for the dominance of matter over antimatter in the Universe. It is pointed out that grand unified theories are not the only providers of a mechanism for baryon number violation; one other possibility, the sphaleron, is briefly explained.

Experiments have been conducted at MIT's Bates Linear Accelerator Center and at the Thomas Jefferson National Accelerator Laboratory to measure parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons. The measurements would yield the Z-exchange form factors and G(super Z) of the proton.

It is easy to construct classical two-state systems illustrating the behavior of the short-lived and long-lived neutral K mesons in the limit of CP conservation. The emulation of CP violation is more tricky, but is provided by the two-dimensional motion of a Foucault pendulum. Analogies are drawn between the pendulum and observables in neutral kaon decays. An emulation of CP and CPT violation using electric circuits is also discussed. [C] 2001 American Association of Physics Teachers. [DOI: 10.1119/1.1289212]

The Stanford Linear Accelerator Center has built a new asymmetric B factory for particle physics studies. The center is working on CP symmetry violation in B meson systems.