First-level trigger systems for LHC experiments

We propose to carry out a broad-based programme of R&D on level-1 trigger systems for LHC experiments. We will consider the overall level-1 which coordinates different subtriggers and which interacts with the front end electronics and with the level-2 system. Careful attention will be paid to systems aspects and problems of synchronization within the pipelined processor system. Trigger algorithms for selecting events with high-pt electrons, photons, muons, jets and large missing Et will be evaluated by physics simulation studies. We will study possible implementations of such trigger algorithms in fast electronics by making conceptual design studies and using behavioural simulation models. For critical areas more detailed design studies will be made, and prototypes of some key elements will be constructed and tested. The proposed R&D project builds on existing studies and will complement other R&D projects already funded by the DRDC

The H1 Neural Network Trigger

At the HERA ep collider the H1 experiment is successfully operating a set of hardwired digital neural networks at the second trigger level. The latency of the network triggers, which are of the feed-forward type, is about 20 microseconds. The inputs to the networks are suitably preprocessed 8 bit quantities, based on the trigger information available from the various subdetectors of H1 at level 1. In this article we describe the principles of the neural hardware trigger and its use within the overall H1 trigger strategy. We concentrate here on the preprocessing of the neural input and discuss further developments for the future high luminosity running at HERA beyond the year 2000. 1 Introduction Since its start in 1992 the HERA ep collider has constantly improved its machine currents and its luminosity. Before the switch to electrons in 1998 the largest integrated luminosity of about 35 pb \Gamma1 was collected in 1997. During these years it became clear that many high cross sectio..

Ionization of Water Clusters Mediated by Exciton Energy Transfer from Argon Clusters

The exciton energy deposited in an argon cluster, (Arn ,< n=20>) using VUV radiation is transferred to softly ionize doped water clusters, ((H2O)n, n=1-9) leading to the formation of non-fragmented clusters. Following the initial excitation, electronic energy is channeled to ionize the doped water cluster while evaporating the Ar shell, allowing identification of fragmented and complete water cluster ions. Examination of the photoionization efficiency curve shows that cluster evaporation from excitons located above 12.6 eV are not enough to cool the energized water cluster ion, and leads to their dissociation to (H2O)n-2H+ (protonated) clusters