This setup seems to create RooDataHist from my datasets so need to rerun and see if the workspaces agree

root [1] RooRealVar xi ("xi","xi",0.1,0.9)
root [2] RooRealVar hpm("hadronPlaneMomentum","hadronPlaneMomentum",0,50000)
root [3] RooDataSet* data = (RooDataSet*)w->data("data_bkg_tt_varIncP1")
root [4] RooDataHist dataHist( "dataHist","dataHist", RooArgSet(xi,hpm),*data)
root [5] RooHistPdf histPdf ("histPdf","histPdf",RooArgSet(xi,hpm),dataHist,9)
root [6] RooPlot* plot = xi.frame()
root [7] RooPlot* plot2 = hpm.frame()
root [8] histPdf.plotOn(plot)
(const class RooPlot*)0x7fd9136a27b0
root [9] histPdf.plotOn(plot2)
(const class RooPlot*)0x7fd91387dc30
root [10] plot->Draw()
Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1
root [11] plot2->Draw()
root [12] histPdf.Print()
RooHistPdf::histPdf[ pdfObs=(xi,hadronPlaneMomentum) ] = 0