Combinatorial Kalman Filter and High Level Trigger Reconstruction for the Belle II Experiment

Track reconstruction at the CMS experiment uses the Combinatorial Kalman Filter. The algorithm computation time scales exponentially with pileup, which will pose a problem for the High Level Trigger at the High Luminosity LHC. FPGAs, which are already used extensively in hardware triggers, are becoming more widely used for compute acceleration. With a combination of high performance, energy efficiency, and predictable and low latency, FPGA accelerators are an interesting technology for high energy physics. Here, progress towards porting of the CMS track reconstruction to Maxeler Technologies’ Dataflow Engines is shown, programmed with their high level language MaxJ. The performance is compared to CPUs, and further steps to optimise for the architecture are presented.

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Software for online reconstruction and filtering at the Belle II experiment

International Journal of Modern Physics A ◽

10.1142/s0217751x20430010 ◽

2020 ◽

Vol 35 (33) ◽

pp. 2043001 ◽

Cited By ~ 1

Author(s):

Nils Braun ◽

Thomas Kuhr

Keyword(s):

Quality Data ◽

Software Components ◽

Data Transport ◽

High Quality Data ◽

Processing Pipeline ◽

Level Trigger ◽

Belle Ii ◽

High Level ◽

Online Reconstruction ◽

Monitoring Information

The Belle II experiment is designed to collect 50 times more data than its predecessor. For a smooth collection of high-quality data, a robust and automated data transport and processing pipeline has been established. We describe the basic software components employed by the high level trigger. It performs a reconstruction of all events using the same algorithms as offline, classifies the events according to physics criteria, and provides monitoring information. The improved system described in this paper has been deployed successfully since 2019.

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The Performance of Belle II High Level Trigger in the First Physics Run

EPJ Web of Conferences ◽

10.1051/epjconf/202024501040 ◽

2020 ◽

Vol 245 ◽

pp. 01040

Author(s):

R. Itoh ◽

N. Braun ◽

C. Li ◽

M. Nakao ◽

S. Yamada ◽

...

Keyword(s):

B Meson ◽

New Physics ◽

Reduction Factor ◽

Pixel Detector ◽

Time Data ◽

High Background ◽

Level Trigger ◽

Belle Ii ◽

High Level ◽

New Generation

The Belle II experiment is a new generation B-factory experiment at KEK in Japan aiming at the search for New Physics in a huge sample of B-meson decays. The commissioning of the accelerator and the detector for the first physics run has started from March this year. The Belle II High Level Trigger (HLT) is fully working in the beam run. The HLT is now operated with 1600 cores clusterized in 5 units, which is 1/4 of the full configuration. The software trigger is performed using the same oﬄine reconstruction code, and events are classified into a set of physics categories. Only the events in the categories of interest are finally sent out to the storage. Live data quality monitoring is also performed on HLT. For the selected events, the reconstructed tracks are extrapolated to the surface of the pixel detector (PXD) and quickly fed back to the readout electronics for the real time data reduction by sending only the associated hits. The maximum trigger rate in the first physics run was 3.5kHz, and the Belle II data acquisition system was stably operated. There were several problems in the HLT operation, but they have successfully been fixed during the data taking period. The HLT reduction factor is measured to be 8 which is still higher than the design because of the high background environment.

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