ATLAS HLT Steering. Andrey Belkin Johannes Gutenberg Universität Mainz

Transcription

1 ATLAS HLT Steering Johannes Gutenberg Universität Mainz 36. Herbstschule für Hochenergiephysik Maria Laach,

2 Overview ATLAS detector Trigger system Steering Performance tests Status and outlook Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 2

3 Physical peculiarities High collision rate: about 40MHz Strong reduction of data rate is needed Background: one physically interesting Event in up to 10 8 Events The Trigger System must be very effective Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 3

4 LHC / ATLAS detector Large Hadron Collider (LHC): p-p Storage Ring at CERN (Geneva), center of mass energy s=14tev, length 26,6 km, design luminosity /(cm 2 s), collision rate 40 MHz ATLAS detector: Angle acceptance ~4π, data channels O(10 8 ), length 40m, height 22m, weight 7000t Muon detectors ( η <2,7) Solenoid magnets (2T) Toroid magnets Main goals: Higgs-Bosons New physics (e.g. SUSY) Electromagnetic calorimeter ( η <5) Hadronic calorimeter ( η <5) Inner detector (Silicon-pixel, -strip Detektoren, Transition Radiation Tracker) Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 4

5 Calorimetry hadronic calorimeter e.m. calorimeter e.m. (e, γ) hadron Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 5

6 Space angles and granularity η = -ln tan(θ/2) Data: isolated traces on e.m./had planes, calorimeter values, tracks, etc. Isolation: a tower upon two calorimeter levels (e.m., had), slides and seeks isolated elements We need to reconstruct the event by given data The main data reduction at the first step is in Regions of Interest concept Areas selected by Trigger - Regions of Interest (RoIs) Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 6

7 Trigger system The idea of three-stage architecture: reject highrated background processes at the earliest possible time leaving complex and slow algorithms for the latest steps. For example, Lvl-1 reduces data of Event to RoIs, Lvl-2 applies calorimeter data, EF applies track and isolation data High-rate process selection in three stages: Level-1 - Data from Calorimeter trigger (analog energy sums from calorimeter cells Δη Δϕ = ), Muon trigger, RoIs, etc. - Trigger decisions within maximum 2 µs Hardware/Firmware implementation - Event rate must be reduced from 40 MHz to khz H L T HLT: Level-2, Event Filter (my part) - Event rate must be reduced from 75 khz to 1-2 khz and then to Hz - Trigger decisions within maximum 1 ms-1 sec Software implementation on a computer farm - Reconstruction and selection of Events Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 7

8 Steering In order to reconstruct the Event we need to apply algorithms that combine all gathered by LVL1 data (energy, RoI, track, etc.) and test if it is physically interesting one For this, the HLT implements Steering, which is a mechanism to drive running of algorithms in certain sequences for classifying and selecting Events according to given schema Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 8

9 EMTAUROI MUONROI HLT workflow tau_cand? g_cand? e_cand? Example: electron reconstruction, at the end we are interested in finding one isolated electron of energy at least 25 GeV In the schema of interesting Events we specify e25i From the LVL1 we receive different RoIs, like EMTAUROI, MUONROI, JETROI, etc. In principle, we need to define in reconstruction sequence that EMTAUROI leads to creation of three hypotheses: tau_cand, g_cand, e_cand The hypotheses are created and passed by Steering to corresponding algorithms that approve or decline them, like L2Alg_ApprECand( ) If the hypothesis is approved the Steering looks into the reconstruction sequence for next hypotheses and algorithms, like e25_calo, e60_calo to EFAlg_ApplyCalo( ), then track and isolation processing If all hypotheses were successful, at the end we will approve the e25i hypothesis and then the Steering will report the match to the schema element e25i and will save the Event Steering L2Alg_ApprECand(...) e_cand! e25_calo? e60_calo?... Steering Schema: e25i... Steering Success! Save Event Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p EFAlg_ApplyCalo(...) e25_calo!... e25i!...

10 Processing buffer (StoreGate) We operate with different objects, like energy, RoIs, etc. This objects are linked to corresponding hypothesis that is just a label, like e25_calo, e25i When the hypothesis is passed to processing, the algorithm retrieves the physical data from storage by hypothesis label Hypotheses and objects are linked together with uses, excludes, seeded by relationships We can navigate through the tree of linked objects in order to obtain all data of each hypothesis Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 10

11 Processing of trigger objects tree EMTAUROI uses Object of EMTauRoi class seeded by tau_cand excludes e_cand g_cand e_cand excludes g_cand tau_cand g_cand excludes e_cand tau_cand Receive input hypothesis Algorithm Navigate through the tree and process data, attach new objects Approve input hypothesis to activate it and initiate the creation of a new hypothesis Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 11

12 Sequences of algorithms and the Menu Sequences <SEQUENCE level="l2" input="emtauroi" algorithm="l2alg_roi2cand/roi2cand/roi2cand" output="e_cand" /> <SEQUENCE level="ef" input="e_cand" algorithm="efalg_cand2calo/cand2calo/cand2calo" output="e25_calo" /> <SEQUENCE level="ef" input="e25_calo" algorithm="efalg_calo2track/calo2track/calo2track" output="e25_track" /> <SEQUENCE level="ef" input="e25_track" algorithm="efalg_track2result/track2result/track2result" output="e25i" /> <SEQUENCE level="ef" input="e_cand" algorithm="efalg_cand2calo/cand2calo/cand2calo" output="e15_calo" /> <SEQUENCE level="ef" input="e15_calo" algorithm="efalg_calo2track/calo2track/calo2track" output="e15_track" /> <SEQUENCE level="ef" input="e15_track" algorithm="efalg_track2result/track2result/track2result" output="e15i" /> Menu <SIGNATURE signature_id="e25i" prescale="1" forced_accept="0"> <TRIGGERELEMENT te_name="e25i" /> </SIGNATURE> <SIGNATURE signature_id="e15ix2" prescale="1" forced_accept="0"> <TRIGGERELEMENT te_name="e15i" /> <TRIGGERELEMENT te_name="e15i" /> </SIGNATURE> Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 12

13 joboption ApplicationMgr.DLLs += { "GaudiAud" }; AuditorSvc.Auditors += { "ChronoAuditor" }; AuditorSvc.Auditors += { "MemStatAuditor" }; // Set output level threshold (2=DEBUG,3=INFO,4=WARNING,5=ERROR,6=FATAL) MemStatAuditor.OutputLevel = 4; MessageSvc.OutputLevel = 2; ApplicationMgr.EvtMax = 10000; TriggerConfig.sequenceListFileLocation = "realseqlist.xml"; TriggerConfig.signatureListFileLocation = "realsiglist.xml"; //... Lvl1Conversion_L2.useL1Simulation = "NO"; Lvl1Conversion_L2.useMuons = "NO"; //... Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 13

14 Tests Ongoing tests of stability and consistence, bugs finding Performance tests Combinatoric explosure checks P4-2GHz standalone, simple menu and sequences: 6-10ms for 1 Event Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 14

15 Current status and outlook Steering, Navigation, Processing buffer, some real algorithms (electromagnetic, partially muon) Performance tests Completing the system Johannes Gutenberg Universität Mainz The ATLAS Trigger System, p. 15