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helicityAngle.cc File Reference

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

Go to the source code of this file.

Functions
double	helicityAngle (const Candidate &cand)
	return the helicity angle of a two body decay with daughter automatically retreived Note: asserts if the candidate does not have two daughters
double	helicityAngle (const reco::Candidate &mother, const reco::Candidate &daughter)
	helicityAngle

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Function Documentation

double helicityAngle

(

const Candidate &

cand

)

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) );
}

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

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

return the helicity angle for two particles.

Definition at line 9 of file helicityAngle.cc.

References h, and reco::Particle::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;  
}

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