The ATLAS B-Physics Trigger

The b-quark production cross-section at the LHC is many orders of magnitude higher than at b-factories. However high event rates makes it necessary to have a very selective trigger system. In addition, the high particle-multiplicity in b-quark events, combined with pile-up of an average of 4.6 interactions per bunch crossing at a luminosity of 2×1033cm−2s−1, gives rise to a large combinatorial background, which must be rejected at the trigger level. This article gives an overview of the ATLAS Trigger system with an emphasis on the B-physics selections.