ISyst.h

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#pragma once

#include <string>

#include "StandardRecord/Proxy/FwdDeclare.h"

namespace ana
{
  /// \brief Encapsulate code to systematically shift a \ref
  /// caf::SRProxy
  ///
  /// The Shift() function alters the \ref caf::StandardRecord or the weight
  /// associated with the event.
  class ISyst
  {
  public:
    ISyst(const std::string& shortName,
          const std::string& latexName);
    ISyst(const ISyst &) = delete;   // no copying.
    ISyst(ISyst && rhs) = delete;    // no moving either.
    virtual ~ISyst();

    ISyst& operator=(const ISyst &) = delete;  // still no copying.
    ISyst& operator=(ISyst &&)      = delete;  // etc.

    /// The name printed out to the screen
    virtual const std::string & ShortName() const final {return fShortName;}

    /// The name used on plots (ROOT's TLatex syntax)
    virtual const std::string & LatexName() const final {return fLatexName;}

    /// \brief Perform the systematic shift
    ///
    /// Override this function if your systematic depends on non-SRNeutrino
    /// quantities. If it is SRNeutrino-only, implement the other function, and
    /// let this default forward to you when necessary.
    ///
    /// \param sigma   Number of sigma to shift record by
    /// \param sr      The record to inspect and alter
    /// \param weight  Scale this weight for reweighting systematics
    virtual void Shift(double sigma, caf::SRProxy* sr, double& weight) const;

    /// For systematics that deal only with the neutrino truth and not any
    /// reconstruction/PID details. Systematics defined this way will work on
    /// nuTree-derived spectra too (e.g. denominators of efficiencies).
    virtual void TruthShift(double sigma,
                            caf::SRNeutrinoProxy* nu,
                            double& weight) const
    {
      // Implement this function if your systematic depends only
      // SRNeutrino. Left blank by default, since systematics using other
      // information can do nothing sensible to the nuTree.
    }

    /// GENIE reweights can only provide +/-1,2sigma
    virtual bool IsGenieReweight() const {return false;}

  private:
    std::string fShortName;
    std::string fLatexName;
  };

} // namespace