The high-rate data challenge: computing for the CBM experiment

V Friese

doi:10.1088/1742-6596/898/11/112003

Abstract

The Compressed Baryonic Matter experiment (CBM) is a next-generation heavy-ion experiment to be operated at the FAIR facility, currently under construction in Darmstadt, Germany. A key feature of CBM is very high interaction rate, exceeding those of contemporary nuclear collision experiments by several orders of magnitude. Such interaction rates forbid a conventional, hardware-triggered readout; instead, experiment data will be freely streaming from self-triggered front-end electronics. In order to reduce the huge raw data volume to a recordable rate, data will be selected exclusively on CPU, which necessitates partial event reconstruction in real-time. Consequently, the traditional segregation of online and offline software vanishes; an integrated on- and offline data processing concept is called for. In this paper, we will report on concepts and developments for computing for CBM as well as on the status of preparations for its first physics run.

Highlights

The experimental setup of Compressed Baryonic Matter experiment (CBM) is depicted in figure 1
It comprises a number of subdetectors, namely the Silicon Tracking System (STS) and the Micro-Vertex Detector (MVD) inside a dipole magnet for track reconstruction, RICH and TRD detectors for electron identification, a TOF detector for hadron identification, an electromagnetic calorimeter for the measurement of neutral probes, and a forward calorimeter (PSD) for event characterisation in terms of centrality and reaction plane angle
Because of the high interaction rates, which do not tolerate a significant trigger latency, and because of the complex trigger signatures which are almost impossible to implement in hardware, CBM chose a readout concept based on self-triggered, free-streaming front-end electronics, which deliver time-stamped data messages to the data acquisition system on activation of a read-out channel above a pre-defined threshold

Summary

Introduction

The experimental setup of CBM is depicted in figure 1. Because of the high interaction rates, which do not tolerate a significant trigger latency, and because of the complex trigger signatures which are almost impossible to implement in hardware, CBM chose a readout concept based on self-triggered, free-streaming front-end electronics, which deliver time-stamped data messages to the data acquisition system on activation of a read-out channel above a pre-defined threshold. Time slices are delivered to the compute nodes, where reconstruction from raw data happens up to a level where the decision to keep or to reject data can be obtained.

Results

Conclusion