A Fast High Resolution Track Trigger for the H1 Experiment

TL;DR

The paper presents a high-resolution, fast track trigger system for the H1 experiment at HERA, enabling real-time 3D track reconstruction to improve event selection at high luminosity.

Contribution

It introduces a novel FPGA-based trigger system capable of reconstructing 3D tracks with high resolution within strict latency constraints.

Findings

Reconstructed tracks down to 100 MeV/c within 23 microseconds

Achieved ~5% momentum resolution at 1 GeV/c

Integrated FPGA and DSP algorithms for real-time processing

Abstract

After 2001 the upgraded ep collider HERA will provide an about five times higher luminosity for the two experiments H1 and ZEUS. In order to cope with the expected higher event rates the H1 collaboration is building a track based trigger system, the Fast Track Trigger (FTT). It will be integrated in the first three levels (L1-L3) of the H1 trigger scheme to provide higher selectivity for events with charged particles. The FTT will allow to reconstruct 3-dimensional tracks in the central drift chamber down to 100 MeV/c within the L2 latency of ~ 23 mus. To reach the necessary momentum resolution of ~ 5% (at 1 GeV/c) sophisticated reconstruction algorithms have to be implemented using high density Field Programmable Gate Arrays (FPGA) and their embedded Content Addressable Memories (CAM). The final track parameter optimization will be done using non-iterative fits implemented in DSPs. While at the first trigger level rough track information will be provided, at L2 tracks with high resolution are available to form trigger decisions on topological and other track based criteria like multiplicities and momenta. At the third trigger level a farm of commercial processor boards will be used to compute physics quantities such as invariant masses.