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[PWGCF] Lambda spin analysis #18159

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[PWGCF] Lambda spin analysis #18159

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a5dbf23
Add independent Lambda event switches and cap mixed-event combinations
Akash-Raj-285 Sep 30, 2026
6e1fa93
Skip empty collisions when counting mixed-event combinations
Akash-Raj-285 Oct 2, 2026
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45 changes: 21 additions & 24 deletions PWGCF/TwoParticleCorrelations/Tasks/lambdaOrAntiLambdaProducerWithSpin.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -1520,6 +1520,7 @@ struct LambdaAntiLambdaPairAnalysis {

// Mixed-Event Compatablity variables
Configurable<float> mixedEventMaxDeltaMultiplicity{"mixedEventMaxDeltaMultiplicity", 10.f, "Maximum multiplicity difference between mixed events"};
Configurable<int> maxMixedEvents{"maxMixedEvents", 200, "Maximum multiplicity-compatible collision combinations with selected candidates in both collisions per dataframe"};

// Short-range pairs
Configurable<float> sameEventShortRangePairMaxDeltaRapidity{"sameEventShortRangePairMaxDeltaRapidity", 0.5f, "ShortRangePai Maximum absolute rapidity difference for same-event pairs"};
Expand Down Expand Up @@ -2258,7 +2259,7 @@ struct LambdaAntiLambdaPairAnalysis {
Preslice<FilteredLambdas> lambdasPerCollision = aod::lambdahyperon::collisionId;
Preslice<FilteredAntiLambdas> antiLambdasPerCollision = aod::lambdahyperon::collisionId;

void processData(CollisionsWithMultiplicity const& collisions, FilteredLambdas const& lambdas, FilteredAntiLambdas const& antiLambdas)
void processSameEventData(CollisionsWithMultiplicity const& collisions, FilteredLambdas const& lambdas, FilteredAntiLambdas const& antiLambdas)
{
static constexpr int MinimumSameSpeciesCandidates = 2;

Expand All @@ -2282,15 +2283,20 @@ struct LambdaAntiLambdaPairAnalysis {
fillAntiLambdaAntiLambdaSameEvent(antiLambdasThisCollision);
}
}
}

// ============================================================
// Mixed events
// ============================================================
void processMixedEventData(CollisionsWithMultiplicity const& collisions, FilteredLambdas const& lambdas, FilteredAntiLambdas const& antiLambdas)
{
int mixedEventCounter = 0;

for (auto const& [collision1, collision2] : combinations(CombinationsStrictlyUpperIndexPolicy(collisions, collisions))) {

const float deltaMultiplicity = std::abs(static_cast<float>(collision1.multNTracksPV()) - static_cast<float>(collision2.multNTracksPV()));

if (mixedEventCounter >= maxMixedEvents) {
break;
}

if (deltaMultiplicity > mixedEventMaxDeltaMultiplicity) {
continue;
}
Expand All @@ -2301,6 +2307,12 @@ struct LambdaAntiLambdaPairAnalysis {
const auto antiLambdas1 = antiLambdas.sliceBy(antiLambdasPerCollision, collision1.globalIndex());
const auto antiLambdas2 = antiLambdas.sliceBy(antiLambdasPerCollision, collision2.globalIndex());

// Empty collisions must not consume the mixing allowance.
if ((lambdas1.size() == 0 && antiLambdas1.size() == 0) ||
(lambdas2.size() == 0 && antiLambdas2.size() == 0)) {
continue;
}

// Lambda–anti-Lambda requires at least one of each.
if (lambdas1.size() > 0 && antiLambdas2.size() > 0) {
fillLambdaAntiLambdaMixedEvent(lambdas1, antiLambdas2);
Expand All @@ -2316,33 +2328,18 @@ struct LambdaAntiLambdaPairAnalysis {
if (antiLambdas1.size() > 0 && antiLambdas2.size() > 0) {
fillAntiLambdaAntiLambdaMixedEvent(antiLambdas1, antiLambdas2);
}

++mixedEventCounter;
}
}

void processDummy(aod::Collisions const&) {}

PROCESS_SWITCH(LambdaAntiLambdaPairAnalysis, processData, "Run candidate production", true);
PROCESS_SWITCH(LambdaAntiLambdaPairAnalysis, processSameEventData, "Run same-event pair analysis", true);
PROCESS_SWITCH(LambdaAntiLambdaPairAnalysis, processMixedEventData, "Run mixed-event pair analysis", false);
PROCESS_SWITCH(LambdaAntiLambdaPairAnalysis, processDummy, "Skip candidate production", false);
};

/*WorkflowSpec defineDataProcessing(ConfigContext const& cfgc)
{
const bool isMC = cfgc.options().get<bool>("isMC");

WorkflowSpec workflow;

if (isMC) {
workflow.push_back(adaptAnalysisTask<LambdaAntiLambdaMcRecoTableProducer>(cfgc));
workflow.push_back(adaptAnalysisTask<LambdaAntiLambdaEfficiencyPlots>(cfgc));
workflow.push_back(adaptAnalysisTask<LambdaAntiLambdaSelectionCutFlow>(cfgc));
} else {
workflow.push_back(adaptAnalysisTask<LambdaOrAntiLambdaProducerWithSpin>(cfgc));
workflow.push_back(adaptAnalysisTask<LambdaAntiLambdaSelector>(cfgc));
workflow.push_back(adaptAnalysisTask<LambdaAntiLambdaPairAnalysis>(cfgc));
}

return workflow;
}*/

WorkflowSpec defineDataProcessing(ConfigContext const& cfgc)
{
return WorkflowSpec{
Expand Down
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