Keeping track of the big event

The BaBar detector at the B meson factory at the Stanford Linear Accelerator Laboratory (SLAC) is physically large. It represents a collaboration of more than 600 researchers at 73 institutions in Europe and North America. The experiment is primarily designed to answer a really big question: why more matter than anti matter survived a fraction of a second after the Big Bang. Several times a person's height and weighing more than 1000 tons, the BaBar detector sits at the intersection point of the electron and positron beams. A silicon vertex detector, comprising strips of silicon spaced 100 microns apart, provides 150000 channels of raw data. The software that controls and processes data from this experiment is also large; an estimated three million lines of code primarily written in C++, with small amounts of Java and Fortran. Because of the complexity, coding standards and tools for managing the code have been developed. The computing environment for BaBar is divided into two parts: the online system and the offline system.