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W. H. Smith
segments (1.25 ◦ each) to the XFT “Linker system” modules which cover 15 ◦ each
and are matched to the segmentation of the trigger signals from the muon and
calorimeter systems. The results from the linker system were passed to the Track
Extrapolation System (XTRP), which sent one or more bits in 2.5 ◦ segmentation
to the muon trigger systems set according to the calculated p T , φ and multiple
scattering. The XTRP also sent a set of 4 bits (for four momentum thresholds) for
each 15 ◦ calorimeter wedge to the Level-1 calorimeter trigger. Finally the XTRP
created a Level-2 tracking trigger based on the number of tracks and their p T and φ
information.
The DØ experiment Central Tracking Trigger (CTT) used information from
the Central Fiber Tracker (CFT) and the Central Preshower System (CPS). Hit
information from each of the 80 axial sectors of the CFT/CPS detectors was fed
through boards programmed with 16,000 Boolean equations that identified patterns
of hits likely to be produced by a charged particle. A list of tracks in four momentum
ranges between 1.5 and 10 GeV/c was then sent to the L1 muon trigger system [6].
The DØ L1 CTT also identified the number of tracks in each event for each of these
four momentum ranges, whether a coincident CPS hit had been found, and whether
the track was isolated. This information was also used in the DØ L1T decision. The
DØ CTT had an efficiency of 97.3 ± 0.1% for tracks with p T > 10 GeV/c [4].
Although both ATLAS and CMS are planning the use of Tracking information at
Level-1 in their designs for the High Luminosity LHC (HL-LHC) project [22], this
information was not included in Run-1 or Run-2.
12.1.7 Global Triggers
An experiment Global Trigger accepts muon, calorimeter and tracking (if available)
trigger information, synchronizes matching sub-system data arriving at different
times and communicates the Level-1 decision to the timing, trigger and control
system for distribution to the sub-systems to initiate the readout. The global trigger
decision is made using logical combinations of the input trigger data. Besides
handling physics triggers, the Global Trigger provides for test and calibration runs,
not necessarily in phase with the machine, and for prescaled triggers, as this is
an essential requirement for checking trigger efficiencies and recording samples of
large cross section data.
The ATLAS Level-1 Global trigger is called the Central Trigger Processor (CTP).
It combines information on the multiplicities of calorimeter and muon trigger
objects which have sufficiently high momentum. These are electrons/photons, taus,
jets, and muons. These are also the “seeds” for the Level-2 trigger that are sent to the
Region of Interest Builder (RoIB). In addition, threshold information on the global
transverse energy and missing energy sums is also used in the Level-1 decision.
In Run-1, the CTP discriminated the delivered multiplicities of the trigger objects
against multiplicity conditions and then combined these conditions to form more
complex triggers when multiple object triggers are needed. In Run-2, the ATLAS
W. H. Smith
segments (1.25 ◦ each) to the XFT “Linker system” modules which cover 15 ◦ each
and are matched to the segmentation of the trigger signals from the muon and
calorimeter systems. The results from the linker system were passed to the Track
Extrapolation System (XTRP), which sent one or more bits in 2.5 ◦ segmentation
to the muon trigger systems set according to the calculated p T , φ and multiple
scattering. The XTRP also sent a set of 4 bits (for four momentum thresholds) for
each 15 ◦ calorimeter wedge to the Level-1 calorimeter trigger. Finally the XTRP
created a Level-2 tracking trigger based on the number of tracks and their p T and φ
information.
The DØ experiment Central Tracking Trigger (CTT) used information from
the Central Fiber Tracker (CFT) and the Central Preshower System (CPS). Hit
information from each of the 80 axial sectors of the CFT/CPS detectors was fed
through boards programmed with 16,000 Boolean equations that identified patterns
of hits likely to be produced by a charged particle. A list of tracks in four momentum
ranges between 1.5 and 10 GeV/c was then sent to the L1 muon trigger system [6].
The DØ L1 CTT also identified the number of tracks in each event for each of these
four momentum ranges, whether a coincident CPS hit had been found, and whether
the track was isolated. This information was also used in the DØ L1T decision. The
DØ CTT had an efficiency of 97.3 ± 0.1% for tracks with p T > 10 GeV/c [4].
Although both ATLAS and CMS are planning the use of Tracking information at
Level-1 in their designs for the High Luminosity LHC (HL-LHC) project [22], this
information was not included in Run-1 or Run-2.
12.1.7 Global Triggers
An experiment Global Trigger accepts muon, calorimeter and tracking (if available)
trigger information, synchronizes matching sub-system data arriving at different
times and communicates the Level-1 decision to the timing, trigger and control
system for distribution to the sub-systems to initiate the readout. The global trigger
decision is made using logical combinations of the input trigger data. Besides
handling physics triggers, the Global Trigger provides for test and calibration runs,
not necessarily in phase with the machine, and for prescaled triggers, as this is
an essential requirement for checking trigger efficiencies and recording samples of
large cross section data.
The ATLAS Level-1 Global trigger is called the Central Trigger Processor (CTP).
It combines information on the multiplicities of calorimeter and muon trigger
objects which have sufficiently high momentum. These are electrons/photons, taus,
jets, and muons. These are also the “seeds” for the Level-2 trigger that are sent to the
Region of Interest Builder (RoIB). In addition, threshold information on the global
transverse energy and missing energy sums is also used in the Level-1 decision.
In Run-1, the CTP discriminated the delivered multiplicities of the trigger objects
against multiplicity conditions and then combined these conditions to form more
complex triggers when multiple object triggers are needed. In Run-2, the ATLAS