The DO Run II Luminosity Monitor

The DO Run II Luminosity Monitor consists of plastic scintillation detectors with fine-mesh photomultiplier readout that cover the range 2.7 < \eta\ < 4.4 in pseudorapidity. The detector is designed to provide a precise measurement of the rate for non-diffractive inelastic collisions that is used to calculate the Tevatron luminosity at DO. Excellent time-of-flight resolution allows a clean separation between beam-beam interactions and the principal background fi om beam halo. In addition, timing is used to measure the position of the primary interaction vertex and to detect multiple interactions, Accurate correction for multiple proton-antiproton interactions in a single beam crossing is essential for an accurate luminosity determination. Associated electronics provide a single-interaction trigger term for the DO Level 1 trigger, and readout of the photomultiplier timing and pulse-height measurements.