CERN Accelerating science

ATLAS Note
Report number	ATL-DAQ-PROC-2016-012
Title	Physics performances with the new ATLAS Level-1 Topological trigger in Run 2
Author(s)	Artz, Sebastian (Institut fuer Physik, Universitaet Mainz)
Corporate Author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Publication	2016
Imprint	24 Aug 2016
Number of pages	5
In:	PoS LHCP2016 (2016) 200
In:	4th Conference on Large Hadron Collider Physics 2016 (LHCP 2016), Lund, Sweden, 13 - 18 Jun 2016, pp.200
DOI	10.22323/1.276.0200
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	L1Topo ; topological processor ; trigger upgrade
Abstract	The ATLAS trigger system aims at reducing the 40 MHz proton-proton collision event rate to a manageable event storage rate of 1 kHz, preserving events valuable for physics analysis. The Level-1 trigger is the first rate-reducing step in the ATLAS trigger system, with an output rate of 100 kHz and decision latency of less than 2.5 micro seconds. It is composed of the calorimeter trigger, muon trigger and central trigger processor. During the last upgrade, a new electronics element was introduced to Level-1: The Topological Processor System. It will make it possible to use detailed realtime information from the Level-1 calorimeter and muon triggers, processed in individual state of the art FPGA processors to determine angles between jets and/or leptons and calculate kinematic variables based on lists of selected/sorted objects. More than one hundred VHDL algorithms are producing trigger outputs to be incorporated into the central trigger processor. This information will be essential to improve background rejection and increase the significance of a large spectrum of ATLAS physics measurements. An overview of the firmware implementation, algorithms performance and their impact on physics results will be illustrated.
Copyright/License	Preprint: (License: CC-BY-4.0)

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