Triggering on Heavy Flavors at Hadron Colliders

For a number of interesting processes in the sector of heavy flavors, the quality of measurements made at hadron colliders is very similar to the quality achieved at e⁺e⁻ colliders (known as B factories). The key to performing such measurements in a hadron environment is the ability to select rare processes from background in real time, that is, to trigger on them. Two distinctive features of heavy-flavor decays have been used for this purpose: the presence of leptons in the final state and secondary vertices produced by the relatively long lifetime. The selection of events based on long lifetime, although technically very challenging, is the most inclusive of all such techniques, allowing access to the widest range of channels. The focus of this review is on the innovative concepts that permitted the reconstruction of tracks produced in hadron collisions with sufficient speed and accuracy for use at trigger level to detect heavy-flavor decays.