Legacy Code
TLimit is a legacy interface: there will be no bug fixes nor new developments. Therefore it is not recommended to use it in new long-term production code. But, depending on the context, using TLimit might still be a valid solution. Consider switching to RooStats.
Algorithm to compute 95% CL limits using the Likelihood ratio semi-bayesian method.
Implemented by C. Delaere from the mclimit code written by Tom Junk [HEP-EX/9902006]. See http://cern.ch/thomasj/searchlimits/ecl.html for more details.
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.
The class TLimitDataSource takes the signal, background and data histograms as well as different systematics sources to form the TLimit input.
The class TConfidenceLevel represents the 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.
The actual algorithm...
From an input (TLimitDataSource) it produces an output TConfidenceLevel. For this, nmc Monte Carlo experiments are performed. As usual, the larger this number, the longer the compute time, but the better the result.
Supposing that there is a plotfile.root file containing 3 histograms (signal, background and data), you can imagine doing things like:
std::cout <<
" CLsb : " <<
myconfidence->CLsb() << std::endl;
std::cout <<
"< CLs > : " <<
myconfidence->GetExpectedCLs_b() << std::endl;
std::cout <<
"< CLsb > : " <<
myconfidence->GetExpectedCLsb_b() << std::endl;
std::cout <<
"< CLb > : " <<
myconfidence->GetExpectedCLb_b() << std::endl;
ROOT::Detail::TRangeCast< T, true > TRangeDynCast
TRangeDynCast is an adapter class that allows the typed iteration through a TCollection.
Class to compute 95% CL limits.
A ROOT file is an on-disk file, usually with extension .root, that stores objects in a file-system-li...
TH1 is the base class of all histogram classes in ROOT.
This class serves as input for the TLimit::ComputeLimit method.
static TConfidenceLevel * ComputeLimit(TLimitDataSource *data, Int_t nmc=50000, bool stat=false, TRandom *generator=nullptr)
More information can still be found on this page
- See also
- https://doi.org/10.1088/0954-3899/28/10/313, https://cds.cern.ch/record/451614/files/open-2000-205.pdf
- Note
- see note about: "Should I use TRolke, TFeldmanCousins, TLimit?" in the TRolke class description.
Definition at line 19 of file TLimit.h.