[ROOT] ROOT class computing 95% CL limits using likelihood ratio

From: Rene Brun (Rene.Brun@cern.ch)
Date: Fri Sep 06 2002 - 22:31:37 MEST


Dear Rooters,

A new set of classes by Christophe.Delaere@cern.ch to compute 95% Cl
has been introduced in the development version in CVS.
These classes have been adapted by Christophe from the MCLIMIT code
by Tom Junk.

class TLimit
------------

Algorithm to compute 95% C.L. limits using the Likelihood ratio
semi-bayesian method.
It takes signal, background and data histograms wrapped in a
TLimitDataSource as input and runs a set of Monte Carlo experiments in
order to compute the limits. If needed, inputs are fluctuated according
to systematics. The output is a TConfidenceLevel.
 
class TLimitDataSource 
----------------------
 
Takes the signal, background and data histograms as well as different
systematics sources to form the TLimit input. 
 
class TConfidenceLevel 
----------------------
 
Final result of the TLimit algorithm. It is created just after the
time-consuming part and can be stored in a TFile for further processing.
It contains light methods to return CLs, CLb and other interesting
quantities.          

A new tutorial at $ROOTSYS/tutorials/limit.C illustrates
the use of these new classes.

Many thanks to Christophe for this interesting contribution.

Rene Brun



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