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IntegrandThetaFunction.cc

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#include "PhysicsTools/IsolationUtils/interface/IntegrandThetaFunction.h"

// -*- C++ -*-
//
// Package:    IntegrandThetaFunction
// Class:      IntegrandThetaFunction
// 
//
// Original Author:  Christian Veelken, UC Davis
//         Created:  Thu Nov  2 13:47:40 CST 2006
// $Id: IntegrandThetaFunction.cc,v 1.2 2007/05/28 09:59:50 llista Exp $
//
//

// system include files
#include <iostream>
#include <iomanip>
#include <vector>

// ROOT include files
#include <TMath.h>

// CMSSW include files
#include "FWCore/MessageLogger/interface/MessageLogger.h"

#include "PhysicsTools/IsolationUtils/interface/IntegralOverPhiFunction.h"
#include "DataFormats/Math/interface/normalizedPhi.h"

//
// constructors and destructor
//

IntegrandThetaFunction::IntegrandThetaFunction()
  : ROOT::Math::ParamFunction(3)
{
  theta0_ = 0.; 
  phi0_ = 0.; 
  alpha_ = 0.; 

  fPhi_ = new IntegralOverPhiFunction();
}

IntegrandThetaFunction::IntegrandThetaFunction(const IntegrandThetaFunction& bluePrint)
{
  theta0_ = bluePrint.theta0_;
  phi0_ = bluePrint.phi0_;
  alpha_ = bluePrint.alpha_;

  fPhi_ = new IntegralOverPhiFunction(*bluePrint.fPhi_);
}

IntegrandThetaFunction::~IntegrandThetaFunction()
{
  delete fPhi_;
}

//
// assignment operator
//

IntegrandThetaFunction& IntegrandThetaFunction::operator=(const IntegrandThetaFunction& bluePrint)
{
  theta0_ = bluePrint.theta0_;
  phi0_ = bluePrint.phi0_;
  alpha_ = bluePrint.alpha_;
  
  (*fPhi_) = (*bluePrint.fPhi_);

  return (*this);
}

//
// member functions
//

void IntegrandThetaFunction::SetParameterTheta0(double theta0)
{
  theta0_ = theta0;
}

void IntegrandThetaFunction::SetParameterPhi0(double phi0)
{
  phi0_ = normalizedPhi(phi0); // map azimuth angle into interval [-pi,+pi]
}

void IntegrandThetaFunction::SetParameterAlpha(double alpha)
{
  alpha_ = alpha;
}

void IntegrandThetaFunction::SetParameters(double* param)
{
  theta0_ = param[0];
  phi0_ = param[1];
  alpha_ = param[2];
}

double IntegrandThetaFunction::DoEval(double x) const
{
//--- return zero if theta either close  to zero or close to Pi
//    (numerical expressions might become "NaN"s)
  const double epsilon = 1.e-3;
  if ( x < epsilon || x > (TMath::Pi() - epsilon) ) return 0.;

//--- calculate trigonometric expressions
//    (dependend on angle theta;
//     polar angle of point within cone)
  double sinTheta = TMath::Sin(x);
  double cscTheta = 1./sinTheta;

  double detJacobi = -cscTheta; // partial derrivative dEta/dTheta (for constant particle density in tau id. isolation cone)
  //double detJacobi = 1.; // ordinary solid angle (FOR TESTING ONLY)

//--- evaluate integral over angle phi
//    (azimuth angle of point within cone)
  fPhi_->SetParameterTheta0(theta0_);
  fPhi_->SetParameterPhi0(phi0_);
  fPhi_->SetParameterAlpha(alpha_);

  double integralOverPhi = (*fPhi_)(x);

  if ( debugLevel_ > 0 ) {
    edm::LogVerbatim("") << "integralOverPhi = " << integralOverPhi << std::endl
                         << " theta0 = " << theta0_ << std::endl
                         << " phi0 = " << phi0_ << std::endl
                         << " alpha = " << alpha_ << std::endl
                         << " theta = " << x << std::endl
                         << std::endl;
  }
  
//--- integrand for integration over theta
//    equals 
//      |dEta/dTheta| * integral over phi * sin(theta)
//
//    (o the factor dEta/dTheta represents the particle density as function of theta, 
//       assuming that the particle density is flat in eta;
//     o the factor sin(theta) originates from the solid angle surface element 
//       expressed in spherical polar coordinates)
//
  //return TMath::Abs(detJacobi)*integralOverPhi*sinTheta;
  return TMath::Abs(detJacobi)*integralOverPhi;
}  

double IntegrandThetaFunction::DoDerivative(double x) const
{
//--- virtual function inherited from ROOT::Math::ParamFunction base class;
//    not implemented, because not neccessary, but needs to be defined to make code compile...
  edm::LogWarning("") << "Function not implemented yet !" << std::endl;

  return 0.;
}

void IntegrandThetaFunction::DoParameterGradient(double x, double* paramGradient) const
{
//--- virtual function inherited from ROOT::Math::ParamFunction base class;
//    not implemented, because not neccessary, but needs to be defined to make code compile...
  edm::LogWarning("") << "Function not implemented yet !" << std::endl;
}

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