[PWGLF] adding occupancy selection (#8110)

Co-authored-by: junleekim <junleekim@maccbookjunlee2024.dyndns.cern.ch>

Author: jikim1290

PWGLF/Tasks/Strangeness/lambdapolarization.cxx

@@ -90,6 +90,8 @@ struct lambdapolarization {
   Configurable<bool> cfgPVSel{"cfgPVSel", false, "Additional PV selection flag for syst"};
   Configurable<float> cfgPV{"cfgPV", 8.0, "Additional PV selection range for syst"};
   Configurable<bool> cfgAddEvtSelPileup{"cfgAddEvtSelPileup", false, "flag for additional pileup selection"};
+  Configurable<int> cfgMaxOccupancy{"cfgMaxOccupancy", 999999, "maximum occupancy of tracks in neighbouring collisions in a given time range"};
+  Configurable<int> cfgMinOccupancy{"cfgMinOccupancy", 0, "maximum occupancy of tracks in neighbouring collisions in a given time range"};
 
   Configurable<float> cfgv0radiusMin{"cfgv0radiusMin", 1.2, "minimum decay radius"};
   Configurable<float> cfgDCAPosToPVMin{"cfgDCAPosToPVMin", 0.05, "minimum DCA to PV for positive track"};
@@ -164,6 +166,8 @@ struct lambdapolarization {
       return 4;
     } else if (name.value == "TPCneg") {
       return 5;
+    } else if (name.value == "TPCall") {
+      return 6;
     } else {
       return 0;
     }
@@ -289,6 +293,9 @@ struct lambdapolarization {
     if (cfgAddEvtSelPileup && !collision.selection_bit(o2::aod::evsel::kNoCollInTimeRangeStandard)) {
       return 0;
     }
+    if (collision.trackOccupancyInTimeRange() > cfgMaxOccupancy || collision.trackOccupancyInTimeRange() < cfgMinOccupancy) {
+      return 0;
+    }
 
     return 1;
   } // event selection