P4BaseIPtCotThPhiM.h

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef FOURMOM_P4BASEIPTCOTTHPHIM_H
#define FOURMOM_P4BASEIPTCOTTHPHIM_H
 
// STL includes
#include <cmath>
#include <ostream>
#include <sstream>
#include <iomanip>
 
// CLHEP includes
#include "CLHEP/Vector/LorentzVector.h"
#include "CLHEP/Units/SystemOfUnits.h"
 
class P4BaseIPtCotThPhiM
{
 public:
 
  virtual ~P4BaseIPtCotThPhiM();
 
  // Const methods: 
 
  double px() const;
  double py() const;
  double pz() const;
  virtual double m() const = 0;
  double m2() const;
  double p() const;
  double p2() const;
  double eta() const;
  virtual double phi() const = 0;
  double e() const;
  double et() const;   
  double pt() const;
  virtual double iPt() const = 0;
  double rapidity() const;
  double cosPhi() const;
  double sinPhi() const;
  double tanTh()  const;
  double cosTh() const;
  double sinTh() const;
  virtual double cotTh() const = 0;
  CLHEP::HepLorentzVector hlv() const;
 
  std::ostream& dump( std::ostream& out ) const;
 
  // Non-const methods: 
 
  // Private data: 
 private: 
};
 
inline P4BaseIPtCotThPhiM::~P4BaseIPtCotThPhiM()
{}
 
inline 
double 
P4BaseIPtCotThPhiM::px() const
{ 
  return std::cos(this->phi())/this->iPt();
}
 
inline
double
P4BaseIPtCotThPhiM::py() const
{ 
  return std::sin(this->phi())/this->iPt();
}
 
inline
double
P4BaseIPtCotThPhiM::pz() const
{ 
  return this->cotTh()/this->iPt();
}
 
inline
double
P4BaseIPtCotThPhiM::m2() const 
{ 
  const double mass = this->m();
  return mass*mass;
}
 
inline
double
P4BaseIPtCotThPhiM::p() const 
{ 
  const double theCotTh = this->cotTh();
  return std::sqrt( 1 + theCotTh*theCotTh ) / this->iPt() ;
}
 
inline
double
P4BaseIPtCotThPhiM::p2() const 
{ 
  const double cotTh = this->cotTh();
  const double iPt   = this->iPt();
  return ( 1 + cotTh*cotTh ) / (iPt*iPt) ;
}
 
inline
double
P4BaseIPtCotThPhiM::eta() const 
{
  const double theCotTh = this->cotTh();
  const double aux = std::sqrt(1+theCotTh*theCotTh);
  return -0.5 * std::log( (aux-theCotTh) / (aux+theCotTh) );
}
 
inline
double
P4BaseIPtCotThPhiM::rapidity() const
{
  const double theE=this->e();
  const double thePz=this->pz();
  return 0.5*std::log((theE+thePz)/(theE-thePz));
}
 
 
inline
double
P4BaseIPtCotThPhiM::e() const 
{ 
  const double theM = this->m();
  const double theP = this->p();
  if ( theM == 0. ) {
    return theP;
  } else {
    return std::sqrt( theP*theP + theM*theM ); 
  }
}
 
inline
double
P4BaseIPtCotThPhiM::et() const 
{ 
  const double theE     = this->e();
  const double theCotTh = this->cotTh();
  return theE / std::sqrt( 1 + theCotTh*theCotTh );
}
 
inline
double
P4BaseIPtCotThPhiM::pt() const
{
  return 1./this->iPt();
}
 
inline
double
P4BaseIPtCotThPhiM::tanTh() const 
{ 
  return 1./this->cotTh() ;
}
 
inline
double
P4BaseIPtCotThPhiM::cosTh() const 
{ 
  const double theCotTh  = this->cotTh();
  const double theCotTh2 = theCotTh*theCotTh;
  const double theCosTh  = std::sqrt(theCotTh2/(1.+theCotTh2));
  if ( theCotTh >= 0. ) {
    return  theCosTh;
  } else{
    return -theCosTh;
  }
}
 
inline
double
P4BaseIPtCotThPhiM::sinTh() const 
{ 
  const double theCotTh = this->cotTh();
  return 1. / std::sqrt( 1 + theCotTh*theCotTh );
}
 
inline
double
P4BaseIPtCotThPhiM::cosPhi() const
{
 return std::cos(this->phi());
}
 
inline
double
P4BaseIPtCotThPhiM::sinPhi() const
{
  return std::sin(this->phi());
}
 
inline
CLHEP::HepLorentzVector
P4BaseIPtCotThPhiM::hlv() const
{ 
  //minimize the number of calculation and dereference
  const double thePt    = this->pt();  
  const double theM     = this->m();  
  const double thePx    = thePt*this->cosPhi();
  const double thePy    = thePt*this->sinPhi();
  const double thePz    = thePt * this->cotTh();
  const double theE     = std::sqrt(   thePt * thePt 
                     + thePz * thePz 
                     + theM  *  theM );
 
  return CLHEP::HepLorentzVector( thePx, thePy, thePz, theE );
}
 
inline
std::ostream&
P4BaseIPtCotThPhiM::dump( std::ostream& out ) const
{
  std::stringstream s;
  s << "[ipt,cotTh,phi,m] ="
    << std::right << std::scientific << std::setprecision(8) 
    << std::setw(16) << this->iPt()
    << std::setw(16) << this->cotTh()
    << std::setw(16) << this->phi()
    << std::setw(16) << this->m();
 
  out << s.str();
  
  return out;
}
 
#endif // FOURMOM_P4BASEIPTCOTTHPHIM_H