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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ALICE

Credit: CERN

C Side

A Side

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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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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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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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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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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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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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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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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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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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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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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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Questions?

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BACKUP SLIDES

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Examples of V0 Timing

Run: 179678Production: ESD muons Trigger class: kMUS7

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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