RooFit: number of events does not add up

From: Eduardo J. Ortega U. <ortegaue_at_uregina.ca>
Date: Fri, 11 Apr 2008 16:55:56 -0600


Hi:

I have a histogram with 2000 events, and I am trying to use RootFit to fit it to the sum of two functions (signal and bg). I do RooVoigtian signal("signal", "signal", Mee, mean, gamma, sigma ); RooExponential background( "background", "background", Mee, a );

RooRealVar N1("N1", "number signal", 100, 0., 10000.);
RooRealVar N2("N2", "number background", 10, 0., 10000.);
RooAddPdf model( "model", "model", RooArgList( signal, background ),
RooArgList( N1, N2 ) );
model.fitTo(..., RooFit::Extended( kTRUE ));

But the fitted values I get for N1 and N2 are 1493.34 and 79.87, which  do not add up (by far) to my number of entries in the histo. Shouldn't they be approximately close, or am I musinderstanding something badly of how the fitting works?

Thanks,

-- 
Eduardo J. Ortega U.
Received on Sat Apr 12 2008 - 00:56:06 CEST

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