HessianBreakdown

The ranking of nuisance parameters can be measured in various ways, see ActionCalculateImpacts and ActionCalculateBreakdowns for more details. However, all of these options are very expensive in terms of computing-power. This action provides a shortcut and allows to make breakdowns very quickly, as it estimates the breakdown of systematic uncertainties solely based on the correlation matrix. It can thus be used to generate a breakdown from any fit results that includes a hesse-matrix, covariance-matrix or correlation-matrix and does not require running any additional fits. However, this technique assumes symmetric, gaussian uncertainties on all parameters, and so is often rather inaccurate in realistic scenarios.

Usage:

+HessianBreakdown.observed {
  +combined{
    <fitresult="Significance/FitResults/obsData_muhat">
    <parameter="mu">
    <target="UncertaintyBreakdown/HessianBreakdownData/mu">
  }
}

This action adds a section to the result under the path specified as target that contains all the information needed to make a breakdown plot using the PlotResults action.