Thrust.h

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#ifndef CandUtils_Thrust_h
#define CandUtils_Thrust_h

#include "DataFormats/Math/interface/Vector3D.h"
#include "DataFormats/Candidate/interface/Candidate.h"
#include <vector>
 
class Thrust  {
public:
  typedef math::XYZVector Vector;
  template<typename const_iterator>
  Thrust(const_iterator begin, const_iterator end) :
    thrust_(0), axis_(0, 0, 0), pSum_(0), 
    n_(end - begin), p_(n_) {
    if (n_ == 0) return;
    std::vector<const reco::Candidate*> cands;
    for(const_iterator i = begin; i != end; ++i) {
      cands.push_back(&*i);
    }
    init(cands);
  } 
  double thrust() const { return thrust_; } 
  const Vector& axis() const { return axis_; } 

private:
  double thrust_;
  Vector axis_;
  double pSum_;
  const unsigned int n_;
  std::vector<Vector> p_;

  struct ThetaPhi {
    ThetaPhi(double t, double p) : theta( t ), phi( p ) { }
    double theta, phi;
  };
  double thrust(const Vector & theAxis) const; 
  ThetaPhi initialAxis() const;
  ThetaPhi finalAxis(ThetaPhi) const;
  Vector axis(double theta, double phi) const;
  Vector axis(const ThetaPhi & tp) const  {
    return axis(tp.theta, tp.phi);
  }
  void parabola(double & a, double & b, double & c, 
        const Vector &, const Vector &, const Vector &) const;
  void init(const std::vector<const reco::Candidate*>&);
};

#endif