helicityAngle.cc File Reference

#include "CommonTools/CandUtils/interface/helicityAngle.h"
#include "DataFormats/Candidate/interface/Candidate.h"
#include "CommonTools/CandUtils/interface/Booster.h"
#include <Math/VectorUtil.h>

Go to the source code of this file.

Functions
double	helicityAngle (const reco::Candidate &mother, const reco::Candidate &daughter)
	return the helicity angle for two particles. More...
double	helicityAngle (const Candidate &cand)

Function Documentation

double helicityAngle	(	const reco::Candidate &	mother,
		const reco::Candidate &	daughter
	)

return the helicity angle for two particles.

helicityAngle

Utility function that returns the helicity angle It is defined as the angle between the candidate momentum and one of the daughters momentum in the mother's center-of-mass reference frame. This angle has a two-fold ambiguity (h, pi - h ), and by convention the angle smaller than pi/2 is chosen.

Author

Luca Lista, INFN

Version

Revision

1.7

Id

helicityAngle.h,v 1.7 2007/12/11 08:42:52 hegner Exp

Definition at line 9 of file helicityAngle.cc.

References h, M_PI, and reco::Candidate::p4().

Referenced by helicityAngle().

                                                                                    {
  Particle::Vector boost = mother.p4().BoostToCM();
  Particle::LorentzVector pdau = ROOT::Math::VectorUtil::boost( daughter.p4(), boost );
  double h = ROOT::Math::VectorUtil::Angle( pdau, boost );
  if ( h > M_PI / 2 ) h = M_PI - h;
  return h;  
}

double helicityAngle

(

const reco::Candidate &

c

)

return the helicity angle of a two body decay with daughter automatically retreived Note: asserts if the candidate does not have two daughters

Definition at line 18 of file helicityAngle.cc.

References reco::Candidate::daughter(), helicityAngle(), and reco::Candidate::numberOfDaughters().

                                               {
  assert( cand.numberOfDaughters() == 2 );
  return helicityAngle( cand, *cand.daughter(0) );
}