HemisphereAlgo.h

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#ifndef HemisphereAlgo_h
#define HemisphereAlgo_h

/*  \class HemisphereAlgo
*
*  Class that, given the 4-momenta of the objects in the event, 
*  allows to split up the event into two "hemispheres" according 
*  to different criteria (see below)/
*
*  Authors: Luc Pape & Filip Moortgat      Date: July 2005
*                                          Updated: July 2006
*                                          Updated: 15 Sept 2006

Transported to PAT by Wolfgang Adam and Tanja Rommerskirchen
*
*/
#include "DataFormats/Candidate/interface/Candidate.h"

#include <vector>
#include <iostream>
#include <cmath>

class HemisphereAlgo {
public:
  // There are 2 constructors:
  // 1. Constructor taking as argument vectors of Px, Py, Pz and E of the objects in
  // the event that should be separated, the seeding method and the hemisphere
  // association method,
  // 2. Constructor taking as argument vectors of Px, Py, Pz and E of the objects in
  // the event that should be separated. The seeding method and the hemisphere
  // association method should then be defined by SetMethod(seeding_method, association_method).
  //
  // Seeding method: choice of 2 inital axes
  //   1: 1st: max P ; 2nd: max P * delta R wrt first one
  //   2: 2 objects who give maximal invariant mass (recommended)
  //
  // HemisphereAlgo association method:
  //   1: maximum pt longitudinal projected on the axes
  //   2: minimal mass squared sum of the hemispheres
  //   3: minimal Lund distance (recommended)
  //
  // Note that SetMethod also allows the seeding and/or association method to be
  // redefined for an existing hemisphere object. The GetAxis or GetGrouping is
  // then recomputed using the newly defined methods.
  //

  HemisphereAlgo(const std::vector<reco::CandidatePtr>& componentRefs_,
                 const int seed_method = 0,
                 const int hemisphere_association_method = 0);

  // Destructor
  ~HemisphereAlgo(){};

  std::vector<float> getAxis1();  // returns Nx, Ny, Nz, P, E of the axis of group 1
  std::vector<float> getAxis2();  // returns Nx, Ny, Nz, P, E of the axis of group 2

  // where Nx, Ny, Nz are the direction cosines e.g. Nx = Px/P,
  // P is the momentum, E is the energy

  std::vector<int> getGrouping();  // returns vector with "1" and "2"'s according to
                                   // which group the object belongs
                                   // (order of objects in vector is same as input)

  void SetMethod(int seed_method, int hemisphere_association_method) {
    seed_meth = seed_method;
    hemi_meth = hemisphere_association_method;
    status = 0;
  }  // sets or overwrites the seed and association methods

  void SetNoSeed(int object_number) {
    Object_Noseed[object_number] = 1;
    status = 0;
  }
  // prevents an object from being used as a seed
  // (method introduced on 15/09/06)

private:
  int reconstruct();  // the hemisphere separation algorithm
  std::vector<reco::CandidatePtr> Object;

  std::vector<int> Object_Group;
  std::vector<int> Object_Noseed;

  std::vector<float> Axis1;
  std::vector<float> Axis2;

  //static const float hemivsn = 1.01;
  int seed_meth;
  int hemi_meth;
  int status;
};

#endif