[PWGCF] Adding a task for short range correlations by MartijnLaarhoven · Pull Request #14670 · AliceO2Group/O2Physics

MartijnLaarhoven · 2026-01-28T13:04:47Z

Adding a task for short range correlations as a function of eta

[PWGCF] Adding a task for short range correlations

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Pull request overview

This pull request adds a new di-hadron correlation analysis task that measures short-range correlations as a function of pseudorapidity (η), alongside wiring it into the analysis workflows.

Changes:

Introduces EtaDihadron analysis task implementing η-differential same- and mixed-event di-hadron correlations, including MC and efficiency handling, largely mirroring the existing DiHadronCor task but using η for trigger/associate axes.
Defines new configurable η-binned axes for trigger and associated particles and updates all relevant histograms and correlation containers to use these.
Registers a new DPL workflow eta-dihadron in CMakeLists.txt so the task can be run within the PWGCF TwoParticleCorrelations framework.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
`PWGCF/TwoParticleCorrelations/Tasks/etaDihadron.cxx`	New η-differential di-hadron correlation task, including configuration, event/track selection, efficiency and centrality weighting, same/mixed-event correlation filling, and corresponding MC/efficiency workflows.
`PWGCF/TwoParticleCorrelations/Tasks/CMakeLists.txt`	Adds the `eta-dihadron` workflow target referencing `etaDihadron.cxx` and linking it with the standard PWGCF analysis libraries.

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Copilot · 2026-01-28T13:11:00Z

PWGCF/TwoParticleCorrelations/Tasks/etaDihadron.cxx

+    if (doprocessSame && cfgUseAdditionalEventCut) {
+      registry.add("hEventCountSpecific", "Number of Event;; Count", {HistType::kTH1D, {{12, 0, 12}}});
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(1, "after sel8");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(2, "kNoSameBunchPileup");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(3, "kNoITSROFrameBorder");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(4, "kNoTimeFrameBorder");


hEventCountSpecific is created only when doprocessSame && cfgUseAdditionalEventCut is true, but eventSelected() fills this histogram unconditionally whenever cfgUseAdditionalEventCut is enabled (including when it is called from processMixed). This means that configurations where only the mixed-event processing is enabled with additional event cuts will call registry.fill(HIST("hEventCountSpecific"), ...) on a histogram that was never registered, which can lead to a runtime error. Consider removing the doprocessSame condition when registering hEventCountSpecific, or alternatively guarding all fills in eventSelected() behind the same condition that controls the histogram’s creation.

I would follow Copilot recommendation
If not, why is being used?

victor-gonzalez · 2026-01-28T21:36:12Z

@vkucera has the linter been removed from CI? I don't see it neither in the checks nor its report

vkucera · 2026-01-29T03:26:17Z

@vkucera has the linter been removed from CI? I don't see it neither in the checks nor its report

Yes, it has been disabled temporarily until a vulnerability is fixed. See #14662

victor-gonzalez · 2026-01-29T15:51:08Z

PWGCF/TwoParticleCorrelations/Tasks/etaDihadron.cxx

+      registry.add("hEventCountSpecific", "Number of Event;; Count", {HistType::kTH1D, {{12, 0, 12}}});
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(1, "after sel8");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(2, "kNoSameBunchPileup");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(3, "kNoITSROFrameBorder");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(4, "kNoTimeFrameBorder");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(5, "kIsGoodZvtxFT0vsPV");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(6, "kNoCollInTimeRangeStandard");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(7, "kIsGoodITSLayersAll");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(8, "kNoCollInRofStandard");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(9, "kNoHighMultCollInPrevRof");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(10, "occupancy");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(11, "MultCorrelation");
+      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(12, "cfgEvSelV0AT0ACut");


Avoid using magic numbers
If an enum is defined with the corresponding named constants, the x axis is started in -0.5, and the labels set to the named constant plus one, the named constants can be straight on used when filling the histogram which is less error prone, provides readability and easy expansion in the future

victor-gonzalez · 2026-01-29T15:53:59Z

PWGCF/TwoParticleCorrelations/Tasks/etaDihadron.cxx

+  template <typename TCollision>
+  bool eventSelected(TCollision collision, const int multTrk, const float centrality, const bool fillCounter)
+  {
+    registry.fill(HIST("hEventCountSpecific"), 0.5);


See my previous comment on the histogram definition

victor-gonzalez · 2026-01-29T15:55:21Z

PWGCF/TwoParticleCorrelations/Tasks/etaDihadron.cxx

+  }
+  PROCESS_SWITCH(EtaDihadron, processMCMixed, "Process MC mixed events", false);
+
+  void processOntheflySame(aod::McCollisions::iterator const& mcCollision, aod::McParticles const& mcParticles)


Would not be more readable processOnTheFlySame?

victor-gonzalez · 2026-01-29T15:55:44Z

PWGCF/TwoParticleCorrelations/Tasks/etaDihadron.cxx

+  }
+  PROCESS_SWITCH(EtaDihadron, processOntheflySame, "Process on-the-fly same event", false);
+
+  void processOntheflyMixed(aod::McCollisions const& mcCollisions, aod::McParticles const& mcParticles)


Same but the equivalent

victor-gonzalez

Please, have a look at my comments for future iterations

MartijnLaarhoven added 2 commits January 28, 2026 13:57

Adding a task for short range correlations

26d6b16

Adding a task for short range correlations as a function of eta

Merge pull request #12 from MartijnLaarhoven/MartijnLaarhoven-patch-9

f132bbb

[PWGCF] Adding a task for short range correlations

Copilot AI review requested due to automatic review settings January 28, 2026 13:04

MartijnLaarhoven requested review from alibuild, ariedel-cern, glromane, lauraser, lgraczykCern, otonvd, prchakra, shouqiye, victor-gonzalez and zchochul as code owners January 28, 2026 13:04

github-actions bot added the pwgcf label Jan 28, 2026

github-actions bot changed the title ~~Adding a task for short range correlations~~ [PWGCF] Adding a task for short range correlations Jan 28, 2026

Copilot started reviewing on behalf of MartijnLaarhoven January 28, 2026 13:05 View session

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victor-gonzalez reviewed Jan 29, 2026

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victor-gonzalez approved these changes Jan 29, 2026

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victor-gonzalez merged commit cc62032 into AliceO2Group:master Jan 29, 2026
22 of 23 checks passed

fcolamar pushed a commit to fcolamar/O2Physics that referenced this pull request Feb 4, 2026

[PWGCF] Adding a task for short range correlations (AliceO2Group#14670)

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[PWGCF] Adding a task for short range correlations#14670

[PWGCF] Adding a task for short range correlations#14670
victor-gonzalez merged 2 commits intoAliceO2Group:masterfrom
MartijnLaarhoven:master

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MartijnLaarhoven commented Jan 28, 2026

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Pull request overview

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