MissingMomentum.hh

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// -*- C++ -*-
#ifndef RIVET_MissingMomentum_HH
#define RIVET_MissingMomentum_HH

#include "Rivet/Rivet.hh"
#include "Rivet/Projection.hh"
#include "Rivet/Projections/VisibleFinalState.hh"
#include "Rivet/Particle.hh"
#include "Rivet/Event.hh"

namespace Rivet {


  /// @brief Calculate missing \f$ E \f$, \f$ E_\perp \f$ etc.
  ///
  /// Project out the total visible energy vector, allowing missing
  /// \f$ E \f$, \f$ E_\perp \f$ etc. to be calculated. Final state
  /// visibility restrictions are automatic.
  class MissingMomentum : public Projection {
  public:

    /// Default constructor with uncritical FS.
    MissingMomentum()
    {
      setName("MissingMomentum");
      FinalState fs;
      addProjection(fs, "FS");
      addProjection(VisibleFinalState(fs), "VisibleFS");
    }


    /// Constructor.
    MissingMomentum(const FinalState& fs)
    {
      setName("MissingMomentum");
      addProjection(fs, "FS");
      addProjection(VisibleFinalState(fs), "VisibleFS");
    }


    /// Clone on the heap.
    virtual const Projection* clone() const {
      return new MissingMomentum(*this);
    }


  public:

    /// The vector-summed visible four-momentum in the event.
    /// @note Reverse this vector with operator- to get the missing momentum vector.
    const FourMomentum& visibleMomentum() const { return _momentum; }

    /// The vector-summed visible transverse energy in the event
    /// @note Reverse this vector with operator- to get the missing ET vector.
    const Vector3& vectorEt() const { return _vet; }

    /// The scalar-summed visible transverse energy in the event.
    double scalarEt() const { return _set; }


  protected:

    /// Apply the projection to the event.
    void project(const Event& e);

    /// Compare projections.
    int compare(const Projection& p) const;


  public:

    /// Clear the projection results.
    void clear();


  private:

    /// The total visible momentum
    FourMomentum _momentum;

    /// Scalar transverse energy
    double _set;

    /// Vector transverse energy
    Vector3 _vet;

  };


}

#endif