Si$\Lambda$ViO: A Trigger for $\Lambda$-Hyperons

Abstract

As online trigger for events containing $\Lambda$ hyperons in p+p collisions at $3.1\mathrm{GeV}$ a silicon-based device has been designed and built. This system has been integrated close to the target region within the FOPI spectrometer at GSI and was also employed as a tracking device to improve the vertex reconstruction of secondary decays. The design of the detector components, read-out, the trigger capability as well as the tracking performance are presented. An enrichment factor of about 14 was achieved for events containing a $\Lambda$-hyperon candidate.