Thesis defense of Niklas Nolte

The LHCb experiment at the Large Hadron Collider at CERN is planning a major
detector upgrade for the next data taking period. The instantaneous luminosity
is increased by a factor of five to generate more data per time. The hardware
trigger stage preceding detector readout is removed and LHCb now has to process
30 MHz of incoming events in real time. The work presented in this thesis shows
three contributions towards a fast and efficient trigger system.

The first contribution is a multi-threaded scheduling algorithm to work with
negligible overhead in the Upgrade regime. It is the first implementation for
LHCb capable of realizing arbitrary control and data flow at the required speed.
It restricts itself to inter-event concurrency to avoid costly runtime scheduling
decisions.

The second contribution comprises several algorithms to perform particle combination,
vertexing and selection steps in the second HLT stage. These algorithms
show competitive performances which can speed up the selection stage of HLT2
by orders of magnitude. Employing these algorithms marks a significant step
towards an HLT2 application fast enough for the increased event rate.

The third contribution concerns the most important and most costly HLT2
selection at LHCb, the Topological Trigger. It aims to inclusively capture many
beauty-flavored decay chains. First, the algorithm for event selection is optimized.
In a second step, output bandwidth is reduced significantly by employing a
classification algorithm for selecting additional relevant information present in
the event.

Thesis of Niklas Nolte (2021): A Selection Framework for LHCb's Upgrade Trigger

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