BetaBoostEvtVtxGenerator.cc

Go to the documentation of this file.

/*
  ________________________________________________________________________

  BetaBoostEvtVtxGenerator

  Smear vertex according to the Beta function on the transverse plane
  and a Gaussian on the z axis. It allows the beam to have a crossing
  angle (slopes dxdz and dydz).

  Based on GaussEvtVtxGenerator
  implemented by Francisco Yumiceva (yumiceva@fnal.gov)

  FERMILAB
  2006
  ________________________________________________________________________
*/

//lingshan: add beta for z-axis boost

//#include "IOMC/EventVertexGenerators/interface/BetafuncEvtVtxGenerator.h"

#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Utilities/interface/Exception.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"

#include "FWCore/Framework/interface/EDProducer.h"
#include "FWCore/Utilities/interface/InputTag.h"
#include "FWCore/ServiceRegistry/interface/Service.h"
#include "FWCore/Utilities/interface/RandomNumberGenerator.h"
#include "SimDataFormats/GeneratorProducts/interface/HepMCProduct.h"

#include "CLHEP/Random/RandGaussQ.h"
#include "CLHEP/Units/GlobalSystemOfUnits.h"
#include "CLHEP/Units/GlobalPhysicalConstants.h"
//#include "CLHEP/Vector/ThreeVector.h"
#include "HepMC/SimpleVector.h"
#include "TMatrixD.h"

#include <iostream>

using namespace edm;
using namespace std;
using namespace CLHEP;

namespace CLHEP {
  class HepRandomEngine;
}

class BetaBoostEvtVtxGenerator : public edm::EDProducer{
public:
  BetaBoostEvtVtxGenerator(const edm::ParameterSet & p);
  virtual ~BetaBoostEvtVtxGenerator();

  //virtual CLHEP::Hep3Vector * newVertex();
  virtual HepMC::FourVector* newVertex(CLHEP::HepRandomEngine*) ;
  virtual void produce( edm::Event&, const edm::EventSetup& ) override;
  virtual TMatrixD* GetInvLorentzBoost();


  void sigmaZ(double s=1.0);

  void X0(double m=0) { fX0=m; }
  void Y0(double m=0) { fY0=m; }
  void Z0(double m=0) { fZ0=m; }

  void Phi(double m=0) { phi_=m; }
  void Alpha(double m=0) { alpha_=m; }
  void Beta(double m=0) { beta_=m; }

  void betastar(double m=0) { fbetastar=m; }
  void emittance(double m=0) { femittance=m; }

  double BetaFunction(double z, double z0);

private:
  BetaBoostEvtVtxGenerator(const BetaBoostEvtVtxGenerator &p);
  BetaBoostEvtVtxGenerator&  operator = (const BetaBoostEvtVtxGenerator & rhs );

  double alpha_, phi_;
  //TMatrixD boost_;
  double beta_;
  double fX0, fY0, fZ0;
  double fSigmaZ;
  //double fdxdz, fdydz;
  double fbetastar, femittance;
  double falpha;

  HepMC::FourVector*       fVertex ;
  TMatrixD *boost_;
  double fTimeOffset;
  
  edm::InputTag            sourceLabel;

  bool verbosity_;
};


BetaBoostEvtVtxGenerator::BetaBoostEvtVtxGenerator(const edm::ParameterSet & p ):
  fVertex(0), boost_(0), fTimeOffset(0),
  sourceLabel(p.getParameter<edm::InputTag>("src")),
  verbosity_(p.getUntrackedParameter<bool>("verbosity",false))
{
  fX0 =        p.getParameter<double>("X0")*cm;
  fY0 =        p.getParameter<double>("Y0")*cm;
  fZ0 =        p.getParameter<double>("Z0")*cm;
  fSigmaZ =    p.getParameter<double>("SigmaZ")*cm;
  alpha_ =     p.getParameter<double>("Alpha")*radian;
  phi_ =       p.getParameter<double>("Phi")*radian;
  fbetastar =  p.getParameter<double>("BetaStar")*cm;
  femittance = p.getParameter<double>("Emittance")*cm; // this is not the normalized emittance
  fTimeOffset = p.getParameter<double>("TimeOffset")*ns*c_light; // HepMC time units are mm
  beta_=p.getParameter<double>("Beta"); 
  if (fSigmaZ <= 0) {
    throw cms::Exception("Configuration")
      << "Error in BetaBoostEvtVtxGenerator: "
      << "Illegal resolution in Z (SigmaZ is negative)";
  }

  produces<edm::HepMCProduct>();
  
}

BetaBoostEvtVtxGenerator::~BetaBoostEvtVtxGenerator() 
{
  delete fVertex ;
  if (boost_ != 0 ) delete boost_;
}

//Hep3Vector* BetaBoostEvtVtxGenerator::newVertex() {
HepMC::FourVector* BetaBoostEvtVtxGenerator::newVertex(CLHEP::HepRandomEngine* engine) {

    
  double X,Y,Z;

  double tmp_sigz = CLHEP::RandGaussQ::shoot(engine, 0.0, fSigmaZ);
  Z = tmp_sigz + fZ0;

  double tmp_sigx = BetaFunction(Z,fZ0); 
  // need sqrt(2) for beamspot width relative to single beam width
  tmp_sigx /= sqrt(2.0);
  X = CLHEP::RandGaussQ::shoot(engine, 0.0, tmp_sigx) + fX0; // + Z*fdxdz ;

  double tmp_sigy = BetaFunction(Z,fZ0);
  // need sqrt(2) for beamspot width relative to single beam width
  tmp_sigy /= sqrt(2.0);
  Y = CLHEP::RandGaussQ::shoot(engine, 0.0, tmp_sigy) + fY0; // + Z*fdydz;

  double tmp_sigt = CLHEP::RandGaussQ::shoot(engine, 0.0, fSigmaZ);
  double T = tmp_sigt + fTimeOffset; 

  if ( fVertex == 0 ) fVertex = new HepMC::FourVector();
  fVertex->set(X,Y,Z,T);
        
  return fVertex;
}

double BetaBoostEvtVtxGenerator::BetaFunction(double z, double z0)
{
  return sqrt(femittance*(fbetastar+(((z-z0)*(z-z0))/fbetastar)));

}


void BetaBoostEvtVtxGenerator::sigmaZ(double s) 
{ 
  if (s>=0 ) {
    fSigmaZ=s; 
  }
  else {
    throw cms::Exception("LogicError")
      << "Error in BetaBoostEvtVtxGenerator::sigmaZ: "
      << "Illegal resolution in Z (negative)";
  }
}

TMatrixD* BetaBoostEvtVtxGenerator::GetInvLorentzBoost() {

  //alpha_ = 0;
  //phi_ = 142.e-6;
  //    if (boost_ != 0 ) return boost_;
    
  //boost_.ResizeTo(4,4);
  //boost_ = new TMatrixD(4,4);
  TMatrixD tmpboost(4,4);
  TMatrixD tmpboostZ(4,4);
  TMatrixD tmpboostXYZ(4,4);

  //if ( (alpha_ == 0) && (phi_==0) ) { boost_->Zero(); return boost_; }
    
  // Lorentz boost to frame where the collision is head-on
  // phi is the half crossing angle in the plane ZS
  // alpha is the angle to the S axis from the X axis in the XY plane
    
  tmpboost(0,0) = 1./cos(phi_);
  tmpboost(0,1) = - cos(alpha_)*sin(phi_);
  tmpboost(0,2) = - tan(phi_)*sin(phi_);
  tmpboost(0,3) = - sin(alpha_)*sin(phi_);
  tmpboost(1,0) = - cos(alpha_)*tan(phi_);
  tmpboost(1,1) = 1.;
  tmpboost(1,2) = cos(alpha_)*tan(phi_);
  tmpboost(1,3) = 0.;
  tmpboost(2,0) = 0.;
  tmpboost(2,1) = - cos(alpha_)*sin(phi_);
  tmpboost(2,2) = cos(phi_);
  tmpboost(2,3) = - sin(alpha_)*sin(phi_);
  tmpboost(3,0) = - sin(alpha_)*tan(phi_);
  tmpboost(3,1) = 0.;
  tmpboost(3,2) = sin(alpha_)*tan(phi_);
  tmpboost(3,3) = 1.;
  //cout<<"beta "<<beta_;
  double gama=1.0/sqrt(1-beta_*beta_);
  tmpboostZ(0,0)=gama;
  tmpboostZ(0,1)=0.;
  tmpboostZ(0,2)=-1.0*beta_*gama;
  tmpboostZ(0,3)=0.;
  tmpboostZ(1,0)=0.;
  tmpboostZ(1,1) = 1.;
  tmpboostZ(1,2)=0.;
  tmpboostZ(1,3)=0.;
  tmpboostZ(2,0)=-1.0*beta_*gama;
  tmpboostZ(2,1) = 0.;
  tmpboostZ(2,2)=gama;
  tmpboostZ(2,3) = 0.;
  tmpboostZ(3,0)=0.;
  tmpboostZ(3,1)=0.;
  tmpboostZ(3,2)=0.;
  tmpboostZ(3,3) = 1.;

  tmpboostXYZ=tmpboostZ*tmpboost;
  tmpboostXYZ.Invert();



  boost_ = new TMatrixD(tmpboostXYZ);
  if ( verbosity_ ) { boost_->Print(); }
    
  return boost_;
}

void BetaBoostEvtVtxGenerator::produce( Event& evt, const EventSetup& )
{
  edm::Service<RandomNumberGenerator> rng;
  if (!rng.isAvailable()) {
    throw cms::Exception("Configuration")
      << "Attempt to get a random engine when the RandomNumberGeneratorService is not configured.\n"
         "You must configure the service if you want an engine.\n";
  }
  CLHEP::HepRandomEngine* engine = &rng->getEngine(evt.streamID());
  
  Handle<HepMCProduct> HepUnsmearedMCEvt;
  evt.getByLabel(sourceLabel, HepUnsmearedMCEvt);
  
  // Copy the HepMC::GenEvent
  HepMC::GenEvent* genevt = new HepMC::GenEvent(*HepUnsmearedMCEvt->GetEvent());
  std::unique_ptr<edm::HepMCProduct> HepMCEvt(new edm::HepMCProduct(genevt));

  // generate new vertex & apply the shift 
  //
  HepMCEvt->applyVtxGen( newVertex(engine) ) ;
 
  //HepMCEvt->LorentzBoost( 0., 142.e-6 );
  HepMCEvt->boostToLab( GetInvLorentzBoost(), "vertex" );
  HepMCEvt->boostToLab( GetInvLorentzBoost(), "momentum" );
  evt.put(std::move(HepMCEvt));
  return ;
}

#include "FWCore/Framework/interface/MakerMacros.h"
DEFINE_FWK_MODULE(BetaBoostEvtVtxGenerator);