How to read weights for an unbinned data set

Roofit and RooStats
1

Hello,

I am trying to use a weighted unbinned data set. I do the following:

TFile *f = new TFile(“somefile.root”);
TTree ltr = (TTree)f->Get(“mytree”);

RooRealVar deltam(“dm”,"#Delta M",0.135, 0.17);
RooRealVar w1(“w1”,“pt weight”,0.5, 1.5);
RooCategory c(“cate”,“cate”);
c.defineType(“RC”,+1);
c.defineType(“WC”,-1);

Float_t dm, pt, ptw1;
Int_t rc;

ltr->SetBranchAddress(“dm”,&dm);
ltr->SetBranchAddress(“isrc”,&rc);
ltr->SetBranchAddress(“pt”,&pt);
ltr->SetBranchAddress(“ptwgt1”,&ptw1);

RooDataSet *databin0=new RooDataSet(“databin0”,“All, integrated”,RooArgSet(deltam,w1,c),WeightVar(w1));

Int_t nent=(Int_t)ltr->GetEntries();

for (Int_t i=0; i<nent; i++)
{
ltr->GetEntry(i);
w1=ptw1;

  if(rc==1){c.setLabel("RC");
deltam=dm;}
  if(rc==0){c.setLabel("WC");
deltam=dm;}

  databin0->add(RooArgSet(deltam, w1, c));
  w1.Print();
  databin0->Print();
  cout<<"data weight: "<<databin0->weight()<<endl;

}

The output looks like this:

RooRealVar::w1 = 0.87292 L(0.5 - 1.5)
RooDataSet::databin0[dm,cate,weight:w1] = 2209 entries (2209 weighted)
data weight: 1

To me, it looks like it reads the proper value of the weight, but it fails to consider it as such. Could someone please tell me what am I doing wrong?

Thank you,
Monica

2

Dear Monica,

I share your concern, from what I see the macro seems fine and it is strange that it returns weight=1. I’ll let Wouter comment on the issue.

Regards,

– Gregory