[PWGDQ] Update HistogramsLibrary.cxx (#10686)

Co-authored-by: Debadatta3337 <debadatt.behera@cern.ch>

Author: Debadatta3337

PWGDQ/Core/HistogramsLibrary.cxx

@@ -946,6 +946,7 @@ void o2::aod::dqhistograms::DefineHistograms(HistogramManager* hm, const char* h
       if (subGroupStr.Contains("mult")) {
         hm->AddHistogram(histClass, "Mass_Pt_MultFV0A", "", false, 200, 0.0, 5.0, VarManager::kMass, 40, 0.0, 40.0, VarManager::kPt, 100, 0.0, 25000.0, VarManager::kMultFV0A);
         hm->AddHistogram(histClass, "Mass_VtxNcontribReal", "Mass vs VtxNcontribReal", false, 200, 0.0, 5.0, VarManager::kMass, 200, 0, 200.0, VarManager::kVtxNcontribReal);
+        hm->AddHistogram(histClass, "VtxZ_VtxNcontribReal", "VtxZ vs VtxNcontribReal", false, 240, -12.0, 12.0, VarManager::kVtxZ, 200, 0, 200.0, VarManager::kVtxNcontribReal);
       }
       if (subGroupStr.Contains("polarization")) {
         hm->AddHistogram(histClass, "cosThetaHE", "", false, 100, -1., 1., VarManager::kCosThetaHE);