the atlas trigger & data acquisition system in run-2 · atlas tdaq system - run-2 data...

The ATLAS Trigger & Data Acquisition System in Run-2

Catrin BerniusNew York University

US LHC Users Association MeetingFermilab, Chicago

10.-13. November 2015

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Catrin Bernius, NYU 2

From Run-1 to Run-2The ATLAS trigger system operated successfully in Run-1• Selected events online at √s up to 8 TeV between 2009 and 2013 with high efficiencies for a wide

range of physics processes in ATLAS

In Run-2, trigger rates are expected to increase by a factor of ~5 with the Run-1 trigger system:

• A factor of ~2 due to the energy increase (higher for high pT jets)• A factor of 2-3 due to the luminosity increase

Therefore, additional event rejection is needed via:• Increased trigger thresholds → potential loss of interesting physics• Increased trigger rejection power → improved hardware and

software

→ Improvements & Upgrades to the TDAQ system and software necessary to help reduce the trigger rates to acceptable levels while maintaining or even improving selection efficiencies in the challenging conditions!!

Plots taken from https://twiki.cern.ch/twiki/bin/view/AtlasPublic/TriggerPublicResults


ATLAS TDAQ System - Run-2

Data Acquisition System:

• gather data information from front end electronics from detector to build individual events

• stores data to be sent to permanent storage

• provides control, configuration and monitoring

Trigger • multi-tiered system that decides which events to record• L1: custom electronics to determine Regions-of-Interest (RoIs) in the detector based on coarse

calorimeter and muon information, rate reduction from ~ 30 MHz to 100 kHz• High Level Trigger (HLT): software algorithms running on RoIs or full event information, rate reduction

from 100kHz to 1 kHz (1.5 kHz peak)


TDAQ System - Run-2

FE: Front EndROD: Read Out DeviceHW: HardWareDC: Data CollectorRoI: Region of InterestBE: Back EndROS: ReadOut SystemEB: Event BuilderSFO: SubFarm OutputMUCTPI: Muon to Central Trigger Processor InterfaceTTC: Timing, Trigger Control

CPM: Cluster Processor ModuleCMX: Common Merger eXtended ModuleCTP: Central Trigger ProcessorTP: Topological ProcessornMCM: new Multi Chip ModulePPM: Pre-Processor ModuleJEM: Jet Energy sum ModuleTCG: Thin Gap Chambers

New/Improved for Run-2


TDAQ System - Run-2




Rate reductions • New Multi-Chip Modules: dynamic pedestal subtraction based

on global cell occupancy and position inside a bunch train, improved noise filters

→ significant reduction in L1 ETmiss rates• New coincidence logic between inner muon chambers before

toroid and extended barrel region of Tile calorimeter→ ~50% rate reduction for L1 muons with pT > 20 GeV at 25 ns


TDAQ System - Run-2




L1 Topological Trigger • Programmable topological trigger selections • angular cuts, invariant mass cuts, etc

• Input from L1Calo and L1Muon• Applies selection on trigger objects

→ Low thresholds for multi-object final states possible

Catrin Bernius, NYU

Stable Beams - June 3rd 2015

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Followed by an overall very successful data-taking period for the ATLAS Trigger System!

Catrin Bernius, NYU

2015 Trigger Results

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• Electrons • New fast tracking algorithms• MVA energy calibration• Likelihood identification methods for HLT electron triggers

• Muons:• major rewrite of standalone reconstruction for first muon

identification step• redesigned muon full scan approach gaining factor of ~3 in speed

with no efficiency loss• transverse momentum calculation enhanced using hits from new

chambers in endcaps → factor ~2 resolution improvement

• Jets:• Excellent L1/HLT jet trigger performance• Implemented jet area pileup suppression and jet energy scale

correction

Plots taken from https://twiki.cern.ch/twiki/bin/view/

AtlasPublic/TriggerPublicResults

Catrin Bernius, NYU


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• Missing ET• Use of cell-level information immediately after L1 (coarse

granularity used in Run-1)• Default cell-based algorithms with two-sided two-sigma

noise suppression• Jet based algorithm with soft object correction (mht)• Multitude of topocluster-based algorithms with pileup

suppression (pileup subtraction in rings of pseudo-rapidity (topocIPS), fit-based pileup correction (topocIPUC))

• Taus:• New fast tracking algorithms

followed by full track reconstruction and a BDT-based selection using 13 pile-up corrected variables (calorimeter and tracking information)

• Selections very close to those offline• Possible use of topological

requirements between L1 objects (in commissioning)Plots taken from https://

twiki.cern.ch/twiki/bin/view/AtlasPublic/

TriggerPublicResults

Catrin Bernius, NYU


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• Missing ET• Use of cell-level information immediately after L1 (coarse

granularity used in Run-1)• Default cell-based algorithms with two-sided two-sigma

noise suppression• Jet based algorithm with soft object correction (mht)• Multitude of topocluster-based algorithms with pileup

suppression (pileup subtraction in rings of pseudo-rapidity (topocIPS), fit-based pileup correction (topocIPUC))

• Taus:• New fast tracking algorithms

followed by full track reconstruction and a BDT-based selection using 13 pile-up corrected variables (calorimeter and tracking information)

• Selections very close to those offline• Possible use of topological

requirements between L1 objects (in commissioning)

Overall very successful first year of Run-2 operation for the ATLAS Trigger System!

Looking forward to the coming years!

the atlas trigger & data acquisition system in run-2 · atlas tdaq system - run-2 data...

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