void Onsel_MCMU() {
	gSystem->Load("libRooFit");
	using namespace RooFit;
	
	TFile *f= new TFile("/scratch/cms/guoshuang/rootfiles/CSA07/background/ppmuX/ppmuXOnSel.root");
	TTree *t1= (TTree*)f->Get("EXTree;1");
	RooRealVar MCMU_p("MCMU_p","MCMU_p",0,-50,50) ; 
	RooDataSet data("data","MCMU_p",t1,MCMU_p) ; 
	
	RooPlot* pframe = MCMU_p.frame() ; 
	data.plotOn(pframe,Binning(50),NumCPU(7)) ; 
	pframe->Draw();
}