Correlation with weighted events


I have two MC samples with a different luminosity which correspond to two types of background. I would like to get the correlation between two variables, with both background plotted on the scatter plot. I have to use weights. How can I do it?
So far I calculate the correlation this way (it is just a part of the code) but the fact that luminosities are different is not taken into account:

cout <<"--------------Opening files--------------------------" <<endl;
TFile *fSK =new TFile ("../signal/cocktailMC/Dstar0CPK_K__pi0_KK7forfitWeight.root");

TTree *treeSK =fSK ->Get("ntp999");
Int_t numbSK =treeSK ->GetEntries();
Double_t CorrelationFactorSK;
Int_t entriesSK;

TCut cut="m_deltaE_K_fit>-0.2 && m_deltaE_K_fit<0.2";
TCanvas *canSK=new TCanvas("canSK","Scatter plot mes fit:deltaE_K fit for signal");
    v1SK=  treeSK->GetV1();
    v2SK=  treeSK->GetV2();
 Int_t entriesSK = treeSK->GetSelectedRows();
    mygraphSK = TGraph(entriesSK,v1SK,v2SK);
 Double_t errorSK =TMath::sqrt((1-CorrelationFactorSK*CorrelationFactorSK  )*(1-CorrelationFactorSK*CorrelationFactorSK  )/entriesSK);

Thank you in advance.