A sequential processing strategy for the ATLAS event selection

A new processing strategy for the ATLAS event selection system is proposed for use downstream of the first level trigger. It aims to achieve a reduction of the event rate to a level suitable for recording on permanent storage via a sequential treatment of the "regions of interest" selected by the level 1 trigger. A possible Trigger/DAQ architecture which exploits this concept is presented. It is based on a single processing farm and a network which transports data and protocol traffic. The resources necessary for the implementation of this architecture are estimated. A set of performance figures obtained by calculations and computer simulations are given assuming the use of ATM networking technology.