Allow OB ITSonly (#12420)

* Allow OB ITSonly

* Please consider the following formatting changes

* Rename to avoid confusion

* Please consider the following formatting changes

---------

Co-authored-by: ALICE Action Bot <alibuild@cern.ch>

Author: ddobrigk

Detectors/Vertexing/include/DetectorsVertexing/SVertexerParams.h

@@ -110,6 +110,7 @@ struct SVertexerParams : public o2::conf::ConfigurableParamHelper<SVertexerParam
 
   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 mRejectITSonlyOBtrack = false;    // reject tracks in OB with 4 hits (keep false for more low pt conversions)
   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
@@ -135,8 +136,8 @@ struct SVertexerParams : public o2::conf::ConfigurableParamHelper<SVertexerParam
   //
   // cuts on different Cascade PID params
   bool checkCascadeHypothesis = true;
-  float pidCutsXiMinus[SVertexHypothesis::NPIDParams] = {0.0, 10, 0.0, 4.0, 0.0, 1.56315e-03, 2.23279e-04, 2.75136e-02, 3.309};          // XiMinus
-  float pidCutsOmegaMinus[SVertexHypothesis::NPIDParams] = {0.0, 10, 0.0, 4.0, 0.0, 1.43572e-03, 6.94416e-04, 2.13534e+05, 1.48889e+01}; // OmegaMinus
+  float pidCutsXiMinus[SVertexHypothesis::NPIDParams] = {0.0, 15, 0.01, 4.0, 0.0, 1.56315e-03, 2.23279e-04, 2.75136e-02, 3.309};          // XiMinus
+  float pidCutsOmegaMinus[SVertexHypothesis::NPIDParams] = {0.0, 15, 0.01, 4.0, 0.0, 1.43572e-03, 6.94416e-04, 2.13534e+05, 1.48889e+01}; // OmegaMinus
   float maximalCascadeWidth = 0.006;
   //
   // cuts on different 3 body PID params

Detectors/Vertexing/src/SVertexer.cxx

@@ -513,11 +513,15 @@ void SVertexer::buildT2V(const o2::globaltracking::RecoContainer& recoData) // a
 
       // get Nclusters in the ITS if available
       int8_t nITSclu = -1;
+      bool shortOBITSOnlyTrack = false;
       auto itsGID = recoData.getITSContributorGID(tvid);
       if (itsGID.getSource() == GIndex::ITS) {
         if (isITSloaded) {
           auto& itsTrack = recoData.getITSTrack(itsGID);
           nITSclu = itsTrack.getNumberOfClusters();
+          if (itsTrack.hasHitOnLayer(6) && itsTrack.hasHitOnLayer(5) && itsTrack.hasHitOnLayer(4) && itsTrack.hasHitOnLayer(3)) {
+            shortOBITSOnlyTrack = true;
+          }
         }
       } else if (itsGID.getSource() == GIndex::ITSAB) {
         if (isITSTPCloaded) {
@@ -532,7 +536,7 @@ void SVertexer::buildT2V(const o2::globaltracking::RecoContainer& recoData) // a
         continue;
       }
 
-      if (!hasTPC && nITSclu < mSVParams->mITSSAminNclu) {
+      if (!hasTPC && nITSclu < mSVParams->mITSSAminNclu && (!shortOBITSOnlyTrack || mSVParams->mRejectITSonlyOBtrack)) {
         continue; // reject short ITS-only
       }