Difference: HiggsAnalysisAtATLASUsingRooStats (23 vs. 24)

Revision 242011-08-19 - WilliamBreadenMadden

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-- WilliamBreadenMadden - 2011-08-18
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-- WilliamBreadenMadden - 2011-08-19
 
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  There are instructions on how to use the different versions of ROOT at Glasgow here.
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To check what version of ROOT is running, use the following command:

root -v -b

 

Setting up RooStats

There are three main options available for acquiring ROOT with RooStats included.

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 The hist2workspace executable is used in the following manner: hist2workspace input.xml
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Top-Level XML file

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XML files

 

General description

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A minimum of two XML files are required for configuration. The "top-level" XML file defines the measurement and contains a list of channels that contribute to this measurement. "channel" XML files are used to describe each channel in detail. For each contributing channel, there is a separate XML file.

Top-Level XML file

General description
 This file specifies a top level 'Combination' that is composed of:
  • several 'Channels', which are described in separate XML files.
  • several 'Measurements' (corresponding to a full fit of the model), each of which specifies
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    • whether the tool should export the model only and skip the default fit.
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Specific instructions

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Specific instructions
  There are several parts in the top-level XML file. Initially, the XML schema is specified. The output is specified next. Specifically, the prefix for any output files (ROOT files containing workspaces) is given. Now, the channel XML files are given for each measurement (e.g., signal, background, systematics information) using the Input tag. Next, the details for each channel are defined using the Measurement tag. Which bins to use are specified inclusively using the Measurement tag attributes BinLow and BinHigh. Within the Measurement tag, the POI tag is used to specify the point of interest for the channel, i.e. the test statistic.

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Example file: $ROOTSYS/tutorials/histfactory/example.xml

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Example file: $ROOTSYS/tutorials/histfactory/example.xml
 

<!DOCTYPE Combination  SYSTEM 'HistFactorySchema.dtd'>
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Channel XML files

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Channel XML files

 
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General description

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General description
  These files specify for each channel
  • observed data (if absent, the tool will use the expectation, which is useful for expected sensitivity)
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      • a name (which can be shared with the OverallSyst if correlated).
      • +/- 1 sigma variational histograms.
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Specific instructions

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Specific instructions

First, the channel file specifies the XML schema. Then, the channel is defined and named. The location of the data histogram for the channel is defined. For each background, a Sample is defined. It is specified whether it is normalised to luminosity (i.e., the histograms should be per inverse picobarn and will be scaled). To enable normalisation to luminosity, set the tag attribute NormalizeByTheory to "True". For external normalisation, a data-driven background measurement is fixed to the lumi of the dataset. In this case, set the tag attribute NormalizeByTheory to "False". For the normalisation factor, (e.g., "SigXsecOverSM"), the tag attribute "Name" should match the POI specified in the top level XML configuration file.

Systematic uncertainties
 
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For an overall relative rate systematic, the "OverallSys" tag is used with its appropriate tag attributes. For a shape systematic (a systematic that affects the shape of a histogram), the "HistoSys" tag is used with its appropriate tag attributes. Specifically, for the HistoSys tag attributes "HistoNameHigh" and "HistoNameLow", the respective histograms for the upper and lower shape systematic uncertainties are specified in a manner such as the following:

<HistoSys Name="myShapeSystematic_1" HistoNameHigh="myShapeSystematic_1_high" HistoNameLow="myShapeSystematic_1_low" />
 
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Example file: $ROOTSYS/tutorials/histfactory/example_channel.xml

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Example file: $ROOTSYS/tutorials/histfactory/example_channel.xml
 

<!DOCTYPE Channel  SYSTEM 'HistFactorySchema.dtd'>
 
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