Münster 2017 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 46: Elektronik
T 46.5: Vortrag
Dienstag, 28. März 2017, 12:00–12:15, JUR 5
Online Track and Vertex Reconstruction on GPUs for the Mu3e Experiment — •Dorothea vom Bruch for the Mu3e collaboration — Institut für Kernphysik, Johannes Gutenberg-Universität Mainz
The Mu3e experiment searches for the lepton flavour violating decay µ+ → e+e−e+, aiming at a branching ratio sensitivity better than 10−16. To reach this sensitivity, rates above 109 µ/s are required. A high precision silicon tracking detector combined with excellent timing resolution from scintillating fibers and tiles will measure the momenta, vertices and timing of the decay products of muons stopped in the target to suppress background.
During the first phase of the experiment, a rate of 108 µ/s will be available, resulting in a data rate of ∼ 10 GB/s of zero-suppressed data. The trigger-less readout system consists of optical links and switching FPGAs sending the complete detector data for a time slice to one node of the filter farm. As we can only store ∼ 100 MB/s of data, a full online reconstruction is necessary for an event selection. The highly parallel structure of graphics processing units (GPUs) is ideal for this purpose. An FPGA inside the filter farm PC therefore transfers the event data to the GPU via PCIe direct memory access. The GPU finds and fits tracks using a 3D tracking algorithm for multiple scattering dominated resolution. In a second step, a three track vertex selection is performed, reducing the output data rate to below 100 MB/s by removing combinatorial background. The talk discusses the implementation of the track fit and vertex selection on the GPU.