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ALICE Trigger and Event Selection QA
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By: Kevin McDermott
August 9, 2012
2012 Michigan REU Student Program – Final Presentations
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Kevin McDermott2
ALICE
Credit: CERN
C Side
A Side
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Kevin McDermott3
Min Bias Trigger DetectorsCINT1 Suite = Min Bias TriggerCINT7 Suite = VZERO AND TriggerCINT8 Suite = T0 AND Trigger
Other rare triggers are used, e.g. EMCal and PHOS, but not used for the purpose of this analysis (only muon production for Period LHC12c)
Credit: ALICE-TDR-011
VZERO CVZERO A
T0CT0A
SPD
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Kevin McDermott4
Physics Selection (PS)
PS validates online trigger conditions and rejects background, used offline before any analysis
ALICE, due to various reasons (defocused beams, the vacuum, and long time integration window of TPC), has significantly worse signal-to-background ratio than the other LHC experiments
Stricter event selection by computing the timing of a signal that passes the triggers to ensure that the event passed occurred at the vertex of ALICE (through the VZERO or T0)
Need a high quality data set to do analysis, therefore need to reject background and save actual collisions with high efficiency
Use Quality Assurance (QA) to trend the PS to spot bad runs, monitor beam conditions, and reject clear outliers in analysis
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Kevin McDermott5
ALICE Physics Selection Quality Assurance (PSQA) Old PSQA done primarily by hand, not automatic
Old PSQA needed streamlining and did not meet proper coding conventions
Built a new class to automatically generate text output per run to be used for newly designed online interface
Same class generates ROOT output of trending QA with TGraphErrors
Built a separate class to handle visualization of run by run trending
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Kevin McDermott6
QA Example: Quick Notes
Plots Naming Convention: Trigger Class Name [Fast or Regular] Trigger Logic #
Error bars on plots are smaller than the point size due to zoomed out scale. For ratios that were complete subsets, used binomial errors for
error calculation Otherwise, for uncorrelated ratios, used normal error propagation
The following plot is an example of data taking period LHC12c (May-June 2012) for a given trigger class (in this case, kMUS7)
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Kevin McDermott7
kMUS7: Muon trigger; low pT single muon, offline V0 selection, CINT7 suite
Accepted/All hidden by V0A/All
Special note: Only runs 179678 and 179685 use both CINT7 and CINT8.
Zoom in for example
High BG Run
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Kevin McDermott8
As kMUS7 is a CINT7 trigger (V0 AND), V0A sits opposite muon arm, and explains why Acc/All is close to V0A/All. In the same way, V0A/All and Acc/All inversely proportional to V0A BG/All.
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Kevin McDermott9
kMUS7: Muon trigger; low pT single muon, offline V0 selection, CINT7 suite
V0A/All ≅ Acc/Allinversely proportional to V0A BG/All
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Kevin McDermott10
Online Interface: Workflow
PS: “Trigger Class [Regular or Fast] Trigger #”: Name of Plotted Ratio, Value, ErrorPS: "kMUSH7 [Regular] Trigger 3":Accepted/Trigger_class, 0.363665, 0.00283228
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Kevin McDermott11
Online Interface: Snapshot
Note: This is only a preliminary example. All plots produced by the QA run will be instantly viewable on the web.
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Kevin McDermott12
Summary1. New AliPSQA class can produce a ROOT file with TGraphErrors
that can then be visualized via the AliPSQAVisualization class.
2. PSQA can be performed automatically by setting just a few input and output parameters. AliPSQA produces text files per run that are automatically processed into trending plots on MonALISA, for immediate access for all ALICE members.
3. Trending plots can easily identify runs that are clear outliers to be rejected for data analysis in a given period.
4. When AliPSQA is used in conjunction with run data, trending details are easily understandable.
5. Results of data taking period LHC12c were presented in ALICE official QA meeting.
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Kevin McDermott13
Acknowledgements
Advisors: Alexander Kalweit and Michele Floris
Lab partner: John Groh
Costin Grigoras
Zaida Conesa Del Valle
CERN, ALICE Collaboration, University of Michigan
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Kevin McDermott14
Questions?
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Kevin McDermott15
BACKUP SLIDES
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Kevin McDermott16
Examples of V0 Timing
Run: 179678Production: ESD muons Trigger class: kMUS7
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Kevin McDermott17
Examples of V0 Timing
Run: 180000Production: ESD muons Trigger class: kMUS7
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Parameters for QARuns Analyzed:
179678, 179685, 179687, 179796, 179803, 179837, 179859, 180000, 180037, 180039, 180042, 180044, 180110, 180127, 180129, 180130, 180131, 180132, 180158, 180177, 180189, 180190, 180195, 180199, 180200, 180201, 180225
Period: LHC12c
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Parameters for QAExplanation of QA Data:
Trigger class: Number of events in selected trigger class*Accepted: Accepted eventsV0A and V0C: Events with signal V0A/V0C in collision time window, recomputed offline over all slabsV0A BG and V0C BG: Events flagged as background from V0T0: Events with T0 signal in collision time window, computed offlineT0BG: Events flagged as background from T0FO >= 1: Number of events with more than 1 chip hit in pixels, computed offlineFO >= 2: Number of events with more than 2 chips hit in pixels, computed offlineFO (L1) >= 2: Number of events with more than 2 chip hits in the outer layer of the SPD, computed offline
*For the sake of this presentation, all plots with “Trigger class” are renamed in the legend with “All.”
Reference: https://twiki.cern.ch/twiki/bin/viewauth/ALICE/PWG1EvSelDocumentation
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QA Results
kMUSH7: Muon trigger; high pT single muon, offline V0 selection, CINT7 suite
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QA Results
kMUL7: Muon trigger; like sign dimoun, offline V0 selection, CINT7 suite
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QA Results
kMUU7: Muon trigger; unlike sign dimuon, offline V0 selection, CINT7 suite
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QA Results
kMuonSingleLowPt8: Muon trigger; low pT single muon, offline T0 selection, CINT8 suite
Bad run:already flagged in RCT
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180037 removed.
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kMuonSingleHighPt8: Muon trigger; high pT single muon, offline T0 selection, CINT8 suite
Bad run
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180037 removed.
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kMuonLikeLowPt8: Muon trigger; low pT like sign dimuon, offline T0 selection, CINT8 suite
Bad run
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180037 removed.
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kMuonUnikeLowPt8: Muon trigger; low pT unlike sign dimuon, offline T0 selection, CINT8 suite
Bad run
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180037 removed.
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Online Interface: Parameters
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Online Interface: Notes Class AliPSQA with PSQA.C produce output ROOT file with
TGraphErrors and text files for MonALISA
TGraphErrors can be visualized with PSQAV.C and AliPSQAVisualization class
All cache/output directories made automatically if they do not exist
List of trigger classes and partitions can be hardcoded, would require TString manipulation.
Current limitations: Size of various data members must be changed by hand if number of trigger classes and/or trigger logic increases