Online Track Reconstruction and Level 2 Triggering in NA48

The level 2 trigger on charged particles (L2C) of the NA48 experiment features powerful capabilities for implementing complex triggering algorithms in real-time software. These algorithms may involve track reconstruction, vertex, invariant mass or transverse momentum computation, etc. After a brief outline of the L2C architecture, this paper describes the salient features of the I/O and processing capabilities of the event processor farm, with examples of algorithms that have been effectively implemented within the strong timing constraints of the NA48 level 2 trigger architecture. It concludes with the upgrade possibilities of the system and the possible use of it in other environments with minor changes.