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svertexer tuning (#12270)
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* Min ITS clusters, TPC required for baryons

* Streamline, add rough BB proton sel possibility

* Please consider the following formatting changes

* Change short-ITS-only rej to affect casc only

* Please consider the following formatting changes

* Fix logic back to n-2 commit

* Please consider the following formatting changes

* Change according to option 1 + skip tpc only

* Please consider the following formatting changes

* Fix fullCI

* Please consider the following formatting changes

* Separate min ITS clu cut for track pool + for cascades

* Please consider the following formatting changes

---------

Co-authored-by: David Dobrigkeit Chinellato <david.dobrigkeit.chinellato.cern.ch>
Co-authored-by: ALICE Action Bot <alibuild@cern.ch>
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@ddobrigk @alibuild
ddobrigk and alibuild authored Nov 19, 2023
1 parent 0b3fa30 commit 2766d5d
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Showing 3 changed files with 62 additions and 7 deletions.
8 changes: 8 additions & 0 deletions Detectors/Vertexing/include/DetectorsVertexing/SVertexer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@
#include <algorithm>
#include "GPUO2InterfaceRefit.h"
#include "TPCFastTransform.h"
#include "DataFormatsTPC/PIDResponse.h"

namespace o2
{
Expand Down Expand Up @@ -65,6 +66,7 @@ class SVertexer
using Decay3BodyIndex = o2::dataformats::Decay3BodyIndex;
using RRef = o2::dataformats::RangeReference<int, int>;
using VBracket = o2::math_utils::Bracket<int>;
using PIDResponse = o2::tpc::PIDResponse;

enum HypV0 { Photon,
K0,
Expand Down Expand Up @@ -97,6 +99,9 @@ class SVertexer
GIndex gid{};
VBracket vBracket{};
float minR = 0; // track lowest point r
bool hasTPC = false;
uint8_t nITSclu = -1;
bool compatibleProton = false; // dE/dx compatibility with proton hypothesis (FIXME: use better, uint8_t compat mask?)
};

SVertexer(bool enabCascades = true, bool enab3body = false) : mEnableCascades{enabCascades}, mEnable3BodyDecays{enab3body}
Expand Down Expand Up @@ -183,6 +188,9 @@ class SVertexer
std::vector<DCAFitterN<2>> mFitterV0;
std::vector<DCAFitterN<2>> mFitterCasc;
std::vector<DCAFitterN<3>> mFitter3body;

PIDResponse mPIDresponse;

int mNThreads = 1;
int mNV0s = 0, mNCascades = 0, mN3Bodies = 0, mNStrangeTracks = 0;
float mMinR2ToMeanVertex = 0;
Expand Down
13 changes: 13 additions & 0 deletions Detectors/Vertexing/include/DetectorsVertexing/SVertexerParams.h
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ struct SVertexerParams : public o2::conf::ConfigurableParamHelper<SVertexerParam
float maxDCAXYToMeanVertexV0Casc = 2.; ///< max DCA of V0 from beam line (mean vertex) for cascade V0 candidates
float maxDCAXYToMeanVertex3bodyV0 = 2; ///< max DCA of V0 from beam line (mean vertex) for 3body V0 candidates
float minPtV0 = 0.01; ///< v0 minimum pT
float minPtV0FromCascade = 0.3; ///< v0 minimum pT for v0 to be used in cascading (lowest pT Run 2 lambda: 0.4)
float maxTglV0 = 2.; ///< maximum tgLambda of V0

float causalityRTolerance = 1.; ///< V0 radius cannot exceed its contributors minR by more than this value
Expand Down Expand Up @@ -94,6 +95,18 @@ struct SVertexerParams : public o2::conf::ConfigurableParamHelper<SVertexerParam
float minTPCdEdx = 250; // starting from this dEdx value, tracks with p > minMomTPCdEdx are always accepted
float minMomTPCdEdx = 0.8; // minimum p for tracks with dEdx > mMinTPCdEdx to be accepted

uint8_t mITSSAminNclu = 6; // global requirement of at least this many ITS clusters if no TPC info present (N.B.: affects all secondary vertexing)
uint8_t mITSSAminNcluCascades = 6; // require at least this many ITS clusters if no TPC info present for cascade finding.
bool mRequireTPCforCascBaryons = true; // require that baryon daughter of cascade has TPC
bool mSkipTPCOnlyCascade = true; // skip TPC only tracks when doing cascade finding
bool mSkipTPCOnly3Body = true; // skip TPC only tracks when doing cascade finding

// percent deviation from expected proton dEdx - to be replaced - estimated sigma from TPC for now 6%; a 6*sigma cut is therefore 36% = 0.36f. Any value above 1.0f will be ignored manually when checking.
float mFractiondEdxforCascBaryons = 0.36f;
// default: average 2023 from C. Sonnabend, Nov 2023: ([0.217553 4.02762 0.00850178 2.33324 0.880904 ])
// to-do: grab from CCDB when available -> discussion with TPC experts, not available yet
float mBBpars[5] = {0.217553, 4.02762, 0.00850178, 2.33324, 0.880904};

// cuts on different V0 PID params
bool checkV0Hypothesis = true;
float pidCutsPhoton[SVertexHypothesis::NPIDParams] = {0.001, 20, 0.60, 20, 0.60, 0.0, 0.0, 0.0, 0.0}; // Photon
Expand Down
48 changes: 41 additions & 7 deletions Detectors/Vertexing/src/SVertexer.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -301,6 +301,8 @@ void SVertexer::updateTimeDependentParams()
for (auto& ft : mFitter3body) {
ft.setBz(bz);
}

mPIDresponse.setBetheBlochParams(mSVParams->mBBpars);
}

//______________________________________________
Expand Down Expand Up @@ -429,6 +431,7 @@ void SVertexer::buildT2V(const o2::globaltracking::RecoContainer& recoData) // a
auto trackIndex = recoData.getPrimaryVertexMatchedTracks(); // Global ID's for associated tracks
auto vtxRefs = recoData.getPrimaryVertexMatchedTrackRefs(); // references from vertex to these track IDs
bool isTPCloaded = recoData.isTrackSourceLoaded(GIndex::TPC);
bool isITSloaded = recoData.isTrackSourceLoaded(GIndex::ITS);
if (isTPCloaded && !mSVParams->mExcludeTPCtracks) {
mTPCTracksArray = recoData.getTPCTracks();
mTPCTrackClusIdx = recoData.getTPCTracksClusterRefs();
Expand Down Expand Up @@ -477,15 +480,32 @@ void SVertexer::buildT2V(const o2::globaltracking::RecoContainer& recoData) // a
}
const auto& trc = recoData.getTrackParam(tvid);

bool hasTPC = false;
bool heavyIonisingParticle = false;
bool compatibleWithProton = mSVParams->mFractiondEdxforCascBaryons > 0.999f; // if 1 or above, accept all regardless of TPC
auto tpcGID = recoData.getTPCContributorGID(tvid);
if (tpcGID.isIndexSet() && isTPCloaded) {
hasTPC = true;
auto& tpcTrack = recoData.getTPCTrack(tpcGID);
float dEdxTPC = tpcTrack.getdEdx().dEdxTotTPC;
if (dEdxTPC > mSVParams->minTPCdEdx && trc.getP() > mSVParams->minMomTPCdEdx) // accept high dEdx tracks (He3, He4)
{
heavyIonisingParticle = true;
}
auto protonId = o2::track::PID::Proton;
float dEdxExpected = mPIDresponse.getExpectedSignal(tpcTrack, protonId);
float fracDevProton = std::abs((dEdxTPC - dEdxExpected) / dEdxExpected);
if (fracDevProton < mSVParams->mFractiondEdxforCascBaryons) {
compatibleWithProton = true;
}
}

// get Nclusters in the ITS if available
uint8_t nITSclu = -1;
auto itsGID = recoData.getITSContributorGID(tvid);
if (itsGID.getSource() == GIndex::ITS && isITSloaded) {
auto& itsTrack = recoData.getITSTrack(itsGID);
nITSclu = itsTrack.getNumberOfClusters();
}

if (!acceptTrack(tvid, trc) && !heavyIonisingParticle) {
Expand All @@ -494,9 +514,14 @@ void SVertexer::buildT2V(const o2::globaltracking::RecoContainer& recoData) // a
}
continue;
}

if (!hasTPC && nITSclu < mSVParams->mITSSAminNclu) {
continue; // reject short ITS-only
}

int posneg = trc.getSign() < 0 ? 1 : 0;
float r = std::sqrt(trc.getX() * trc.getX() + trc.getY() * trc.getY());
mTracksPool[posneg].emplace_back(TrackCand{trc, tvid, {iv, iv}, r});
mTracksPool[posneg].emplace_back(TrackCand{trc, tvid, {iv, iv}, r, hasTPC, nITSclu, compatibleWithProton});
if (tvid.getSource() == GIndex::TPC) { // constrained TPC track?
correctTPCTrack(mTracksPool[posneg].back(), mTPCTracksArray[tvid], -1, -1);
}
Expand Down Expand Up @@ -580,11 +605,15 @@ bool SVertexer::checkV0(const TrackCand& seedP, const TrackCand& seedN, int iP,
}
// check tight lambda mass only
bool goodLamForCascade = false, goodALamForCascade = false;
if (mV0Hyps[Lambda].checkTight(p2Pos, p2Neg, p2V0, ptV0)) {
goodLamForCascade = true;
}
if (mV0Hyps[AntiLambda].checkTight(p2Pos, p2Neg, p2V0, ptV0)) {
goodALamForCascade = true;
bool usesTPCOnly = (seedP.hasTPC && seedP.nITSclu < 1) || (seedN.hasTPC && seedN.nITSclu < 1);
bool usesShortITSOnly = (!seedP.hasTPC && seedP.nITSclu < mSVParams->mITSSAminNcluCascades) || (!seedN.hasTPC && seedN.nITSclu < mSVParams->mITSSAminNcluCascades);
if (ptV0 > mSVParams->minPtV0FromCascade && (!mSVParams->mSkipTPCOnlyCascade || !usesTPCOnly) && !usesShortITSOnly) {
if (mV0Hyps[Lambda].checkTight(p2Pos, p2Neg, p2V0, ptV0) && (!mSVParams->mRequireTPCforCascBaryons || seedP.hasTPC) && seedP.compatibleProton) {
goodLamForCascade = true;
}
if (mV0Hyps[AntiLambda].checkTight(p2Pos, p2Neg, p2V0, ptV0) && (!mSVParams->mRequireTPCforCascBaryons || seedN.hasTPC && seedN.compatibleProton)) {
goodALamForCascade = true;
}
}

// apply mass selections for 3-body decay
Expand All @@ -598,7 +627,7 @@ bool SVertexer::checkV0(const TrackCand& seedP, const TrackCand& seedN, int iP,
}

// we want to reconstruct the 3 body decay of hypernuclei starting from the V0 of a proton and a pion (e.g. H3L->d + (p + pi-), or He4L->He3 + (p + pi-)))
bool checkFor3BodyDecays = mEnable3BodyDecays && (!mSVParams->checkV0Hypothesis || good3bodyV0Hyp) && (pt2V0 > 0.5);
bool checkFor3BodyDecays = mEnable3BodyDecays && (!mSVParams->checkV0Hypothesis || good3bodyV0Hyp) && (pt2V0 > 0.5) && (!mSVParams->mSkipTPCOnly3Body || !usesTPCOnly);
bool rejectAfter3BodyCheck = false; // To reject v0s which can be 3-body decay candidates but not cascade or v0
bool checkForCascade = mEnableCascades && r2v0 < mMaxR2ToMeanVertexCascV0 && (!mSVParams->checkV0Hypothesis || (goodLamForCascade || goodALamForCascade));
bool rejectIfNotCascade = false;
Expand Down Expand Up @@ -746,6 +775,11 @@ int SVertexer::checkCascades(const V0Index& v0Idx, const V0& v0, float rv0, std:
continue; // skip the track used by V0
}
auto& bach = tracks[it];

if (!bach.hasTPC && bach.nITSclu < mSVParams->mITSSAminNcluCascades) {
continue; // reject short ITS-only
}

if (bach.vBracket.getMin() > v0vlist.getMax()) {
LOG(debug) << "Skipping";
break; // all other bachelor candidates will be also not compatible with this PV
Expand Down

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