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[PWGLF] Improved mixing in azimuth #14804

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Merged
ktf merged 3 commits into from
Feb 5, 2026
+69 −44
Merged

[PWGLF] Improved mixing in azimuth #14804

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685c185
Add process function for systematic
skundu692 Jan 30, 2026
a360958
Fix clang issue
skundu692 Feb 1, 2026
6e8136e
Fine tuning in mixing
skundu692 Feb 4, 2026
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113 changes: 69 additions & 44 deletions PWGLF/Tasks/Strangeness/lambdaspincorrderived.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -284,9 +284,12 @@ struct lambdaspincorrderived {
if (std::abs(candidate1.lambdaEta() - candidate2.lambdaEta()) > etaMix) {
return false;
}
if (std::abs(RecoDecay::constrainAngle(candidate1.lambdaPhi(), 0.0F, harmonic) - RecoDecay::constrainAngle(candidate2.lambdaPhi(), 0.0F, harmonic)) > phiMix) {
if (std::abs(RecoDecay::constrainAngle(RecoDecay::constrainAngle(candidate1.lambdaPhi(), 0.f, harmonic) - RecoDecay::constrainAngle(candidate2.lambdaPhi(), 0.f, harmonic), -TMath::Pi(), 1)) > phiMix) {
return false;
}
/*if (std::abs(RecoDecay::constrainAngle(candidate1.lambdaPhi(), 0.0F, harmonic) - RecoDecay::constrainAngle(candidate2.lambdaPhi(), 0.0F, harmonic)) > phiMix) {
return false;
}*/
if (std::abs(candidate1.lambdaMass() - candidate2.lambdaMass()) > massMix) {
return false;
}
Expand Down Expand Up @@ -377,7 +380,7 @@ struct lambdaspincorrderived {
double deta2 = particle2.Eta();

// double deta_pair = std::abs(deta1 - deta2);
double dphi_pair = RecoDecay::constrainAngle(particle1.Phi() - particle2.Phi(), -TMath::Pi(), harmonicDphi);
double dphi_pair = RecoDecay::constrainAngle(dphi1 - dphi2, -TMath::Pi(), harmonicDphi);

// double deltaR = TMath::Sqrt(deta_pair * deta_pair + dphi_pair * dphi_pair);
double deltaRap = std::abs(particle1.Rapidity() - particle2.Rapidity());
Expand Down Expand Up @@ -822,7 +825,7 @@ struct lambdaspincorrderived {

// Mass binning: [1.09, 1.14) with 50 bins (1e-3 GeV/c^2)
static constexpr float mMin = 1.09f;
static constexpr float mMax = 1.14f; // exclusive
static constexpr float mMax = 1.14f;
static constexpr int nM_ = 1;
static constexpr float mStep = (mMax - mMin) / nM_;

Expand Down Expand Up @@ -886,6 +889,22 @@ struct lambdaspincorrderived {
return ((((((static_cast<size_t>(colBin) * nStatus + statBin) * nPt + ptBin) * nEta + etaBin) * nPhi + phiBin) * nM + mBin));
}

static inline void collectPhiNeighborBins(int phiB, int nPhi, int nNeighbor, std::vector<int>& out)
{
out.clear();
out.reserve(2 * nNeighbor + 1);
for (int d = -nNeighbor; d <= nNeighbor; ++d) {
int b = phiB + d;
// wrap into [0, nPhi-1]
b %= nPhi;
if (b < 0)
b += nPhi;
out.push_back(b);
}
// optional: unique (in case nNeighbor >= nPhi)
std::sort(out.begin(), out.end());
out.erase(std::unique(out.begin(), out.end()), out.end());
}
// ===================== Main mixing (with mass-bin + random unique sampling) =====================
void processMEV4(EventCandidates const& collisions, AllTrackCandidates const& V0s)
{
Expand Down Expand Up @@ -968,70 +987,76 @@ struct lambdaspincorrderived {
if (status < 0 || status >= nStat)
continue;

// Bin of t1 defines where to search (exact 6D bin)
// Bin of t1 defines where to search (exact bin, but handle φ wrap at edges)
const int ptB = mb.ptBin(t1.lambdaPt());
const int etaB = mb.etaBin(t1.lambdaEta());
const int phiB = mb.phiBin(RecoDecay::constrainAngle(t1.lambdaPhi(), 0.0F, harmonic)); // φ already constrained upstream
const int phiB = mb.phiBin(RecoDecay::constrainAngle(t1.lambdaPhi(), 0.0F, harmonic));
const int mB = mb.massBin(t1.lambdaMass());
if (ptB < 0 || etaB < 0 || phiB < 0 || mB < 0)
continue;

const size_t key = linearKey(colBin, status, ptB, etaB, phiB, mB,
nStat, nPt, nEta, nPhi, nM);
auto const& binVec = buffer[key];
if (binVec.empty())
continue;

// Collect all partners from this 6D bin but different collision
// Collect partners from nominal key, plus wrapped neighbor only for φ-edge bins
std::vector<MatchRef> matches;
matches.reserve(binVec.size());
matches.reserve(128); // or keep binVec.size() if you prefer
const int64_t curColIdx = static_cast<int64_t>(collision1.index());

for (const auto& bc : binVec) {
if (bc.collisionIdx == curColIdx)
continue; // ensure different event
matches.push_back(MatchRef{bc.collisionIdx, bc.rowIndex});
auto collectFrom = [&](int phiBinUse) {
const size_t keyUse = linearKey(colBin, status, ptB, etaB, phiBinUse, mB,
nStat, nPt, nEta, nPhi, nM);
auto const& vec = buffer[keyUse];
for (const auto& bc : vec) {
if (bc.collisionIdx == curColIdx) {
continue; // must be from different event
}
auto tX = V0s.iteratorAt(static_cast<uint64_t>(bc.rowIndex));
if (!selectionV0(tX)) {
continue;
}
if (!checkKinematics(t1, tX)) {
continue;
}
matches.push_back(MatchRef{bc.collisionIdx, bc.rowIndex});
}
};

// 1) nominal φ-bin
collectFrom(phiB);

// 2) wrap only at boundaries: 0 <-> nPhi-1
if (phiB == 0) {
collectFrom(nPhi - 1);
} else if (phiB == nPhi - 1) {
collectFrom(0);
}
if (matches.empty())

if (matches.empty()) {
continue;
}

// ---------- YOUR PREFERRED RANDOM UNIQUE SAMPLING BLOCK ----------
const int cap = nEvtMixing.value;
const int n = static_cast<int>(matches.size());
if (cap > 0 && cap < n) {
std::uniform_int_distribution<int> dist(0, n - 1);
// pick cap unique indices
std::unordered_set<int> chosen;
chosen.reserve(cap * 2);
while ((int)chosen.size() < cap) {
chosen.insert(dist(rng));
}
std::vector<MatchRef> subset;
subset.reserve(cap);
for (int idx : chosen)
subset.push_back(matches[idx]);
matches.swap(subset);
} else {
std::shuffle(matches.begin(), matches.end(), rng);
// Optional safety: dedupe exact same (collision,row) just in case
std::sort(matches.begin(), matches.end(),
[](auto& a, auto& b) { return std::tie(a.collisionIdx, a.rowIndex) < std::tie(b.collisionIdx, b.rowIndex); });
matches.erase(std::unique(matches.begin(), matches.end(),
[](auto& a, auto& b) { return a.collisionIdx == b.collisionIdx && a.rowIndex == b.rowIndex; }),
matches.end());
if (matches.empty()) {
continue;
}
// ----------------------------------------------------------------

const float wBase = 1.0f / static_cast<float>(matches.size());

// Emit mixed pairs: tX replaces t1; keep t2
for (const auto& m : matches) {
auto tX = V0s.iteratorAt(m.rowIndex); // replace accessor if different
if (!selectionV0(tX))
continue; // optional extra guard
if (!checkKinematics(t1, tX))
continue;
auto tX = V0s.iteratorAt(static_cast<uint64_t>(m.rowIndex));

auto proton = ROOT::Math::PtEtaPhiMVector(tX.protonPt(), tX.protonEta(), tX.protonPhi(), o2::constants::physics::MassProton);
auto lambda = ROOT::Math::PtEtaPhiMVector(tX.lambdaPt(), tX.lambdaEta(), tX.lambdaPhi(), tX.lambdaMass());
auto proton2 = ROOT::Math::PtEtaPhiMVector(t2.protonPt(), t2.protonEta(), t2.protonPhi(), o2::constants::physics::MassProton);
auto lambda2 = ROOT::Math::PtEtaPhiMVector(t2.lambdaPt(), t2.lambdaEta(), t2.lambdaPhi(), t2.lambdaMass());

const float dPhi = RecoDecay::constrainAngle(RecoDecay::constrainAngle(lambda.Phi(), 0.0F, harmonic) - RecoDecay::constrainAngle(lambda2.Phi(), 0.0F, harmonic), -TMath::Pi(), harmonicDphi);
const float dPhi = RecoDecay::constrainAngle(
RecoDecay::constrainAngle(lambda.Phi(), 0.0F, harmonic) - RecoDecay::constrainAngle(lambda2.Phi(), 0.0F, harmonic),
-TMath::Pi(), harmonicDphi);

histos.fill(HIST("deltaPhiMix"), dPhi, wBase);
fillHistograms(tX.v0Status(), t2.v0Status(), lambda, lambda2, proton, proton2, 1, wBase);
}
Expand Down
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