BetaBoostEvtVtxGenerator.cc

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/*
  ________________________________________________________________________

  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/Framework/interface/ConsumesCollector.h"
#include "FWCore/Utilities/interface/InputTag.h"
#include "FWCore/ServiceRegistry/interface/Service.h"
#include "FWCore/Utilities/interface/RandomNumberGenerator.h"
#include "FWCore/Utilities/interface/EDGetToken.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);
  ~BetaBoostEvtVtxGenerator() override;

  //virtual CLHEP::Hep3Vector * newVertex();
  virtual HepMC::FourVector* newVertex(CLHEP::HepRandomEngine*);
  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) = delete;
  BetaBoostEvtVtxGenerator& operator=(const BetaBoostEvtVtxGenerator& rhs) = delete;

  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::EDGetTokenT<HepMCProduct> sourceLabel;

  bool verbosity_;
};

BetaBoostEvtVtxGenerator::BetaBoostEvtVtxGenerator(const edm::ParameterSet& p)
    : fVertex(nullptr),
      boost_(nullptr),
      fTimeOffset(0),
      sourceLabel(consumes<HepMCProduct>(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_ != nullptr)
    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 == nullptr)
    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.getByToken(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);