ALICE Trigger and Event
Selection QA
1 Kevin McDermott
By: Kevin McDermott August 9, 2012
ALICE
Credit: CERN
C Side A Side
Min Bias Trigger Detectors
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CINT1 Suite = Min Bias Trigger
CINT7 Suite = VZERO AND Trigger CINT8 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 C VZERO A T0C T0A SPD
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
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
kMUS7: Muon trigger; low pT single muon, offline V0 selection, CINT7 suite
7 Kevin McDermott
Accepted/All
hidden by V0A/All
Special note: Only runs 179678 and 179685 use both CINT7 and CINT8. Zoom in for example
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.
kMUS7: Muon trigger; low pT single muon, offline V0 selection, CINT7 suite
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V0A/All
≅
Acc/All inversely proportional to V0A BG/AllOnline Interface: Workflow
PS: “Trigger Class [Regular or Fast] Trigger #”: Name of Plotted Ratio, Value, Error
Online Interface: Snapshot
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Summary
1. 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.
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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BACKUP SLIDES
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Examples of V0 Timing
Run: 179678
Production: ESD muons Trigger class: kMUS7
Examples of V0 Timing
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Run: 180000
Production: ESD muons Trigger class: kMUS7
Parameters for QA
Runs 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
Parameters for QA
Explanation of QA Data:Trigger class: Number of events in selected trigger class*
Accepted: Accepted events
V0A and V0C: Events with signal V0A/V0C in collision time window, recomputed offline over all slabs
V0A BG and V0C BG: Events flagged as background from V0
T0: Events with T0 signal in collision time window, computed offline
T0BG: Events flagged as background from T0
FO >= 1: Number of events with more than 1 chip hit in pixels, computed offline
FO >= 2: Number of events with more than 2 chips hit in pixels, computed offline
FO (L1) >= 2: Number of events with more than 2 chip hits in the outer layer of the SPD, computed offline
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*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
QA Results
QA Results
kMUL7: Muon trigger; like sign dimoun, offline V0 selection, CINT7 suite
QA Results
QA Results
kMuonSingleLowPt8: Muon trigger; low pT single muon, offline T0 selection,
CINT8 suite 23 Kevin McDermott
Bad run:
already flagged in RCT
kMuonSingleHighPt8: Muon trigger; high pT single muon, offline T0 selection,
CINT8 suite 25 Kevin McDermott
kMuonLikeLowPt8: Muon trigger; low pT like sign dimuon, offline T0 selection,
CINT8 suite 27 Kevin McDermott
kMuonUnikeLowPt8: Muon trigger; low pT unlike sign dimuon, offline T0 selection,
CINT8 suite 29 Kevin McDermott
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