GaisserParam_module.cc

Go to the documentation of this file.

////////////////////////////////////////////////////////////////////////
/// \file  GaisserParam_module.cc
/// \brief Generator for cosmic-rays
///
/// Module designed to produce muons for a MC event using a Gaissers
/// parametisation.
/// For a description of how to use the module see DUNE DocDB 10741
/// It is highly reccommended that you read it before use.....
///
/// \author  k.warburton@sheffield.ac.uk
////////////////////////////////////////////////////////////////////////

// C++ includes.
#include <iostream>
#include <sstream>
#include <string>
#include <cmath>
#include <memory>
#include <utility>
#include <sys/stat.h>
#include <exception>
#include <map>
#include <algorithm>

// Framework includes
#include "art/Framework/Core/EDProducer.h"
#include "art/Framework/Principal/Event.h"
#include "fhiclcpp/ParameterSet.h"
#include "art/Framework/Services/Registry/ServiceHandle.h"
#include "art_root_io/TFileService.h"
#include "art/Framework/Core/ModuleMacros.h"
#include "messagefacility/MessageLogger/MessageLogger.h"
#include "cetlib_except/exception.h"

// art extensions
#include "nurandom/RandomUtils/NuRandomService.h"

// nusimdata includes
#include "nusimdata/SimulationBase/MCTruth.h"
#include "nusimdata/SimulationBase/MCParticle.h"

// lar includes
#include "larcore/Geometry/Geometry.h"
#include "larcoreobj/SummaryData/RunData.h"

#include "TVector3.h"
#include "TDatabasePDG.h"
#include "TF2.h"
#include "TH1.h"
#include "TFile.h"
#include "TAxis.h"
#include "TTree.h"

#include "CLHEP/Random/RandFlat.h"
#include "CLHEP/Random/RandGaussQ.h"

namespace evgen {

  /// module to produce single or multiple specified particles in the detector
  class GaisserParam : public art::EDProducer {

  public:
    explicit GaisserParam(fhicl::ParameterSet const& pset);

  private:

    // This is called for each event.
    void produce(art::Event& evt) override;
    void beginJob() override;
    void beginRun(art::Run& run) override;

    // Defining private maps.......
    typedef std::map<double, TH1*> dhist_Map;
    typedef std::map<double, TH1*>::iterator dhist_Map_it;
    TFile* m_File;
    dhist_Map* m_PDFmap;
    TH1* m_thetaHist;

    void SampleOne(unsigned int i, simb::MCTruth &mct, CLHEP::HepRandomEngine& engine);
    void Sample(simb::MCTruth &mct, CLHEP::HepRandomEngine& engine);

    std::pair<double,double> GetThetaAndEnergy(double rand1, double rand2);
    void MakePDF();
    void ResetMap();
    double GaisserMuonFlux_Integrand(Double_t *x, Double_t *par);
    double GaisserFlux(double e, double theta);
    std::vector<double> GetBinning(const TAxis* axis, bool finalEdge=true);

    CLHEP::HepRandomEngine& fEngine;     ///< art-managed random-number engine

    static constexpr int kGAUS = 1;

    int                 fMode;           ///< Particle Selection Mode
                                         ///< 0--generate a list of all particles,
                                         ///< 1--generate a single particle selected randomly from the list
    bool                fPadOutVectors;  ///< Select to pad out configuration vectors if they are not of
                                         ///< of the same length as PDG
                                         ///< false: don't pad out - all values need to specified
                                         ///< true: pad out - default values assumed and printed out
    std::vector<int>    fPDG;            ///< PDG code of particles to generate
    int                 fCharge;         ///< Charge
    std::string         fInputDir;       ///< Input Directory

    double              fEmin;           ///< Minimum Kinetic Energy (GeV)
    double              fEmax;           ///< Maximum Kinetic Energy (GeV)
    double              fEmid;           ///< Energy to go from low to high (GeV)
    int                 fEBinsLow;       ///< Number of low energy Bins
    int                 fEBinsHigh;      ///< Number of high energy Bins

    double              fThetamin;       ///< Minimum theta
    double              fThetamax;       ///< Maximum theta
    int                 fThetaBins;      ///< Number of theta Bins

    double              fXHalfRange;           ///< Max X position
    double              fYInput;           ///< Max Y position
    double              fZHalfRange;           ///< Max Z position

    double              fT0;             ///< Central t position (ns) in world coordinates
    double              fSigmaT;         ///< Variation in t position (ns)
    int                 fTDist;          ///< How to distribute t  (gaus, or uniform)

    bool                fSetParam;       ///< Which version of Gaissers Param
    bool                fSetRead;        ///< Whether to Read
    bool                fSetWrite;       ///< Whether to Write
    bool                fSetReWrite;     ///< Whether to ReWrite pdfs
    double              fEpsilon;        ///< Minimum integration sum....

    //Define TFS histograms.....
    /*
    TH1D* fPositionX;
    TH1D* fPositionY;
    TH1D* fPositionZ;
    TH1D* fTime;
    TH1D* fMomentumHigh;
    TH1D* fMomentum;
    TH1D* fEnergy;
    TH1D* fDirCosineX;
    TH1D* fDirCosineY;
    TH1D* fDirCosineZ;
    TH1D* fTheta;
    TH1D* fPhi;
    */
    //Define some variables....
    double fCryoBoundaries[6];
    double xNeg    = 0;
    double xPos    = 0;
    double zNeg    = 0;
    double zPos    = 0;
    double fCenterX= 0;
    double fCenterZ= 0;

    // TTree
    TTree* fTree;
    double Time, Momentum, KinEnergy, Gamma, Energy, Theta, Phi, pnorm;
    double XPosition, YPosition, ZPosition, DirCosineX, DirCosineY, DirCosineZ;
  };
}

namespace evgen{

  //____________________________________________________________________________
  GaisserParam::GaisserParam(fhicl::ParameterSet const& pset)
    : art::EDProducer{pset}
    // create a default random engine; obtain the random seed from NuRandomService,
    // unless overridden in configuration with key "Seed"
    , fEngine(art::ServiceHandle<rndm::NuRandomService>{}->createEngine(*this, pset, "Seed"))
    , fMode         {pset.get< int                 >("ParticleSelectionMode")}
    , fPadOutVectors{pset.get< bool                >("PadOutVectors")}
    , fPDG          {pset.get< std::vector<int>    >("PDG")}
    , fCharge       {pset.get< int >("Charge")}
    , fInputDir     {pset.get< std::string         >("InputDir")}
    , fEmin         {pset.get< double              >("Emin")}
    , fEmax         {pset.get< double              >("Emax")}
    , fEmid         {pset.get< double              >("Emid")}
    , fEBinsLow     {pset.get< int                 >("EBinsLow")}
    , fEBinsHigh    {pset.get< int                 >("EBinsHigh")}
    , fThetamin     {pset.get< double              >("Thetamin")}
    , fThetamax     {pset.get< double              >("Thetamax")}
    , fThetaBins    {pset.get< int                 >("ThetaBins")}
    , fXHalfRange   {pset.get< double              >("XHalfRange")}
    , fYInput       {pset.get< double              >("YInput")}
    , fZHalfRange   {pset.get< double              >("ZHalfRange")}
    , fT0           {pset.get< double              >("T0")}
    , fSigmaT       {pset.get< double              >("SigmaT")}
    , fTDist        {pset.get< int                 >("TDist")}
    , fSetParam     {pset.get< bool                >("SetParam")}
    , fSetRead      {pset.get< bool                >("SetRead")}
    , fSetWrite     {pset.get< bool                >("SetWrite")}
    , fSetReWrite   {pset.get< bool                >("SetReWrite")}
    , fEpsilon      {pset.get< double              >("Epsilon")}
  {
    produces< std::vector<simb::MCTruth> >();
    produces< sumdata::RunData, art::InRun >();
  }

  //____________________________________________________________________________
  void GaisserParam::beginJob()
  {
    //Work out center of cryostat(s)
    art::ServiceHandle<geo::Geometry const> geom;
    for (unsigned int i=0; i < geom->Ncryostats() ; i++ ) {
      geom->CryostatBoundaries(fCryoBoundaries, i);
      if ( xNeg > fCryoBoundaries[0] ) xNeg = fCryoBoundaries[0];
      if ( xPos < fCryoBoundaries[1] ) xPos = fCryoBoundaries[1];
      if ( zNeg > fCryoBoundaries[4] ) zNeg = fCryoBoundaries[4];
      if ( zPos < fCryoBoundaries[5] ) zPos = fCryoBoundaries[5];
      }
    fCenterX = xNeg + (xPos-xNeg)/2;
    fCenterZ = zNeg + (zPos-zNeg)/2;

    // Make the Histograms....
    art::ServiceHandle<art::TFileService const> tfs;
    /*
    fPositionX    = tfs->make<TH1D>("fPositionX"   ,"Position (cm)" ,500,fCenterX-(fXHalfRange+10) ,fCenterX+(fXHalfRange+10));
    fPositionY    = tfs->make<TH1D>("fPositionY"   ,"Position (cm)" ,500,-(fYInput+10),(fYInput+10));
    fPositionZ    = tfs->make<TH1D>("fPositionZ"   ,"Position (cm)" ,500,fCenterZ-(fZHalfRange+10) ,fCenterZ+(fZHalfRange+10));
    fTime         = tfs->make<TH1D>("fTime"        ,"Time (s)"      ,500,0,1e6);
    fMomentumHigh = tfs->make<TH1D>("fMomentumHigh","Momentum (GeV)",500,0,fEmax);
    fMomentum     = tfs->make<TH1D>("fMomentum"    ,"Momentum (GeV)",500,0,100);
    fEnergy       = tfs->make<TH1D>("fEnergy"      ,"Energy (GeV)"  ,500,0,fEmax);

    fDirCosineX = tfs->make<TH1D>("fDirCosineX","Normalised Direction cosine",500,-1,1);
    fDirCosineY = tfs->make<TH1D>("fDirCosineY","Normalised Direction cosine",500,-1,1);
    fDirCosineZ = tfs->make<TH1D>("fDirCosineZ","Normalised Direction cosine",500,-1,1);

    fTheta      = tfs->make<TH1D>("fTheta"     ,"Angle (radians)",500,-365,365);
    fPhi        = tfs->make<TH1D>("fPhi"       ,"Angle (radians)",500,-365,365);
    */
    fTree = tfs->make<TTree>("Generator","analysis tree");
    fTree->Branch("XPosition" ,&XPosition ,"XPosition/D" );
    fTree->Branch("YPosition" ,&YPosition ,"YPosition/D" );
    fTree->Branch("ZPosition" ,&ZPosition ,"ZPosition/D" );
    fTree->Branch("Time"      ,&Time      ,"Time/D"      );
    fTree->Branch("Momentum"  ,&Momentum  ,"Momentum/D"  );
    fTree->Branch("KinEnergy" ,&KinEnergy ,"KinEnergy/D" );
    fTree->Branch("Energy"    ,&Energy    ,"Energy/D"    );
    fTree->Branch("DirCosineX",&DirCosineX,"DirCosineX/D");
    fTree->Branch("DirCosineY",&DirCosineY,"DirCosineY/D");
    fTree->Branch("DirCosineZ",&DirCosineZ,"DirCosineZ/D");
    fTree->Branch("Theta"     ,&Theta     ,"Theta/D"     );
    fTree->Branch("Phi"       ,&Phi       ,"Phi/D"       );
  }

  //____________________________________________________________________________
  void GaisserParam::beginRun(art::Run& run)
  {
    // Check fcl parameters were set correctly
    if ( fThetamax > M_PI/2 + 0.01 ) throw cet::exception("GaisserParam")<< "\nThetamax has to be less than " << M_PI/2 << ", but was entered as " << fThetamax << ", this cause an error so leaving program now...\n\n";
    if ( fThetamin < 0         )     throw cet::exception("GaisserParam")<< "\nThetamin has to be more than 0, but was entered as " << fThetamin << ", this cause an error so leaving program now...\n\n" << std::endl;
    if ( fThetamax < fThetamin )     throw cet::exception("GaisserParam")<< "\nMinimum angle is bigger than maximum angle....causes an error so leaving program now....\n\n" << std::endl;

    // grab the geometry object to see what geometry we are using
    art::ServiceHandle<geo::Geometry const> geo;
    run.put(std::make_unique<sumdata::RunData>(geo->DetectorName()));
    MakePDF ();
  }

  //____________________________________________________________________________
  void GaisserParam::produce(art::Event& evt)
  {
    ///unique_ptr allows ownership to be transferred to the art::Event after the put statement
    std::unique_ptr< std::vector<simb::MCTruth> > truthcol(new std::vector<simb::MCTruth>);

    simb::MCTruth truth;
    truth.SetOrigin(simb::kSingleParticle);

    Sample(truth, fEngine);

    MF_LOG_DEBUG("GaisserParam") << truth;

    truthcol->push_back(truth);

    evt.put(std::move(truthcol));
  }

  //____________________________________________________________________________
  // Draw the type, momentum and position of a single particle from the
  // FCIHL description
  void GaisserParam::SampleOne(unsigned int i, simb::MCTruth &mct, CLHEP::HepRandomEngine& engine){

    CLHEP::RandFlat   flat(engine);
    CLHEP::RandGaussQ gauss(engine);

    Time = Momentum = KinEnergy = Gamma = Energy = Theta = Phi = pnorm = 0.0;
    XPosition = YPosition = ZPosition = DirCosineX = DirCosineY = DirCosineZ = 0.0;

    TVector3 x;
    TVector3 pmom;

    // set track id to -i as these are all primary particles and have id <= 0
    int trackid = -1*(i+1);
    std::string primary("primary");

    // Work out whether particle/antiparticle, and mass...
    double m =0.0;
    fPDG[i] = 13;
    if (fCharge == 0 ) {
      if(1.0-2.0*flat.fire() > 0) fPDG[i]=-fPDG[i];
    }
    else if ( fCharge == 1 ) fPDG[i] = 13;
    else if ( fCharge == 2 ) fPDG[i] = -13;
    static TDatabasePDG  pdgt;
    TParticlePDG* pdgp = pdgt.GetParticle(fPDG[i]);
    if (pdgp) m = pdgp->Mass();

    // Work out T0...
    if(fTDist==kGAUS){
      Time = gauss.fire(fT0, fSigmaT);
    }
    else {
      Time = fT0 + fSigmaT*(2.0*flat.fire()-1.0);
    }

    // Work out Positioning.....
    x[0] = (1.0 - 2.0*flat.fire())*fXHalfRange + fCenterX;
    x[1] = fYInput;
    x[2] = (1.0 - 2.0*flat.fire())*fZHalfRange + fCenterZ;

    // Make Lorentz vector for x and t....
    TLorentzVector pos(x[0], x[1], x[2], Time);

    // Access the pdf map which has been loaded.....
    if(m_PDFmap) {

      //---- get the muon theta and energy from histograms using 2 random numbers
      std::pair<double,double> theta_energy; //---- muon theta and energy
      theta_energy = GetThetaAndEnergy(flat.fire(),flat.fire());

      //---- Set theta, phi
      Theta = theta_energy.first;  // Angle returned by GetThetaAndEnergy between 0 and pi/2
      Phi   = M_PI*( 1.0-2.0*flat.fire() ); // Randomly generated angle between -pi and pi

      //---- Set KE, E, p
      KinEnergy = theta_energy.second; // Energy returned by GetThetaAndEnergy
      Gamma         = 1 + (KinEnergy/m);
      Energy        = Gamma * m;
      Momentum      = std::sqrt(Energy*Energy-m*m); // Get momentum

      pmom[0] = Momentum*std::sin(Theta)*std::cos(Phi);
      pmom[1] = -Momentum*std::cos(Theta);
      pmom[2] = Momentum*std::sin(Theta)*std::sin(Phi);

      pnorm   = std::sqrt( pmom[0]*pmom[0] + pmom[1]*pmom[1] + pmom[2]*pmom[2] );
      DirCosineX = pmom[0] / pnorm;
      DirCosineY = pmom[1] / pnorm;
      DirCosineZ = pmom[2] / pnorm;
    }
    else {
      std::cout << "MuFlux map hasn't been initialised, aborting...." << std::endl;
      return;
    }

    TLorentzVector pvec(pmom[0], pmom[1], pmom[2], Energy );

    simb::MCParticle part(trackid, fPDG[i], primary);
    part.AddTrajectoryPoint(pos, pvec);
    /*
    fTree->Branch();
    fTree->Branch();
    fTree->Branch();
    fPositionX    ->Fill (x[0]);
    fPositionY    ->Fill (x[1]);
    fPositionZ    ->Fill (x[2]);
    fTime         ->Fill (Time);
    fMomentumHigh ->Fill (Momentum);
    fMomentum     ->Fill (Momentum);
    fEnergy       ->Fill (Energy);
    fDirCosineX   ->Fill (DirCosineX);
    fDirCosineY   ->Fill (DirCosineY);
    fDirCosineZ   ->Fill (DirCosineZ);
    fTheta        ->Fill (Theta*180/M_PI);
    fPhi          ->Fill (Phi  *180/M_PI);
    */
    XPosition = x[0];
    YPosition = x[1];
    ZPosition = x[2];

    std::cout << "Theta: " << Theta << " Phi: " << Phi << " KineticEnergy: " << KinEnergy << " Energy: " << Energy << " Momentum: " << Momentum << std::endl;
    std::cout << "x: " <<  pos.X() << " y: " << pos.Y() << " z: " << pos.Z() << " time: " << pos.T() << std::endl;
    std::cout << "Px: " <<  pvec.Px() << " Py: " << pvec.Py() << " Pz: " << pvec.Pz() << std::endl;
    std::cout << "Normalised..." << DirCosineX << " " << DirCosineY << " " << DirCosineZ << std::endl;

    fTree->Fill();
    mct.Add(part);
  }

  //____________________________________________________________________________
  void GaisserParam::Sample(simb::MCTruth &mct, CLHEP::HepRandomEngine& engine)
  {
    switch (fMode) {
    case 0: // List generation mode: every event will have one of each
            // particle species in the fPDG array
      for (unsigned int i=0; i<fPDG.size(); ++i) {
        SampleOne(i, mct, engine);
      }//end loop over particles
      break;
    case 1: // Random selection mode: every event will exactly one particle
            // selected randomly from the fPDG array
      {
        CLHEP::RandFlat flat(engine);

        unsigned int i=flat.fireInt(fPDG.size());
        SampleOne(i, mct, engine);
      }
      break;
    default:
      mf::LogWarning("UnrecognizeOption") << "GaisserParam does not recognize ParticleSelectionMode "
                                          << fMode;
      break;
    } // switch on fMode

    return;
  }

  //__________________________________
  std::pair<double,double> GaisserParam::GetThetaAndEnergy(double rand1, double rand2)
  {
    if(rand1 < 0 || rand1 > 1) std::cerr << "GetThetaAndEnergy:\tInvalid random number " << rand1 << std::endl;
    if(rand2 < 0 || rand2 > 1) std::cerr << "GetThetaAndEnergy:\tInvalid random number " << rand2 << std::endl;

    int thetaBin = 0;
    m_thetaHist->GetBinWithContent(double(rand1),thetaBin,1,m_thetaHist->GetNbinsX(),1.0);
    if(m_thetaHist->GetBinContent(thetaBin) < rand1) thetaBin += 1;
    double drand1 = (m_thetaHist->GetBinContent(thetaBin) - rand1)/(m_thetaHist->GetBinContent(thetaBin) - m_thetaHist->GetBinContent(thetaBin-1));
    double thetaLow = m_thetaHist->GetXaxis()->GetBinLowEdge(thetaBin);
    double thetaUp  = m_thetaHist->GetXaxis()->GetBinUpEdge(thetaBin);
    double theta = drand1*(thetaUp-thetaLow) + thetaLow;

    int energyBin = 0;
    TH1* energyHist = 0;
    bool notFound = true;
    for(dhist_Map_it mapit=m_PDFmap->begin(); mapit!=m_PDFmap->end(); mapit++){
      if( fabs(mapit->first+thetaLow)<0.000001 ) {
        energyHist = mapit->second;
        notFound = false;
        break;
      }
    }
    if(notFound) std::cout << "GetThetaAndEnergy: ERROR:\tInvalid theta!" << std::endl;
    //  MSG("string = " << To_TString(thetaLow) << ", double = " << thetaLow );

    energyHist->GetBinWithContent(double(rand2),energyBin,1,energyHist->GetNbinsX(),1.0);
    if(energyHist->GetBinContent(energyBin) < rand2) energyBin += 1;
    double drand2 = (energyHist->GetBinContent(energyBin) - rand2)/(energyHist->GetBinContent(energyBin) - energyHist->GetBinContent(energyBin-1));
    double energyLow = energyHist->GetXaxis()->GetBinLowEdge(energyBin);
    double energyUp  = energyHist->GetXaxis()->GetBinUpEdge(energyBin);
    double energy = drand2*(energyUp-energyLow) + energyLow;
    //  MSG("MuFlux::GetThetaEnergy()\te = " << energy*1000. );

    return std::make_pair(theta,energy);
  }

  //____________________________________________________________________________
  void GaisserParam::MakePDF()
  {
    std::cout << "In my function MakePDF" << std::endl;
    m_File=0;
    m_PDFmap=0;
    m_thetaHist=0;
    double TotalMuonFlux=0;

    if(m_PDFmap){
      std::cout << "PDFMAP" << std::endl;
      if(m_PDFmap->size()>0 && !fSetReWrite){
        std::cout << "MakePDF: Map has already been initialised. " << std::endl;
        std::cout << "Do fSetReWrite - true if you really want to override this map." << std::endl;
        return;
        }
      std::cout << fSetReWrite << std::endl;
      if(fSetReWrite) ResetMap();
    }
    else{
      m_PDFmap = new dhist_Map;
      std::cout << "Making new dhist_Map called m_PDFmap....." << std::endl;
    }

    TF2* muonSpec = new TF2("muonSpec", this,
                            &evgen::GaisserParam::GaisserMuonFlux_Integrand,
                            fEmin, fEmax, fThetamin, fThetamax, 0,
                            "GaisserParam", "GaisserMuonFlux_Integrand"
                            );
    //--------------------------------------------
    //------------ Compute the pdfs

    //---- compute pdf for the theta
    TotalMuonFlux = muonSpec->Integral(fEmin, fEmax, fThetamin, fThetamax, fEpsilon ); // Work out the muon flux at the surface
    std::cout << "Surface flux of muons = " << TotalMuonFlux << " cm-2 s-1" << std::endl;

    //---- work out if we're reading a file, writing to file, or neither
    std::ostringstream pdfFile;
    pdfFile << "GaisserPDF_"<<fEmin<<"-"<<fEmid<<"-"<<fEmax<<"-"<< fEBinsLow<<"-"<<fEBinsHigh<<"-"<<fThetamin<<"-"<<fThetamax<<"-"<<fThetaBins<<".root";
    std::string tmpfileName = pdfFile.str();
    std::replace(tmpfileName.begin(),tmpfileName.end(),'+','0');
    if      (tmpfileName == "GaisserPDF_0-100-100100-1000-10000-0-1.5708-100.root")          tmpfileName = "GaisserPDF_DefaultBins.root";
    else if (tmpfileName == "GaisserPDF_0-100-4000-1000-1000-0-1.5708-100.root")             tmpfileName = "GaisserPDF_LowEnergy.root";
    else if (tmpfileName == "GaisserPDF_4000-10000-100000-1000-10000-0-1.5708-100.root")     tmpfileName = "GaisserPDF_MidEnergy.root";
    else if (tmpfileName == "GaisserPDF_100000-500000-1e007-10000-100000-0-1.5708-100.root") tmpfileName = "GaisserPDF_HighEnergy.root";

    std::ostringstream pdfFilePath;
    pdfFilePath << fInputDir << tmpfileName;
    std::string fileName = pdfFilePath.str();

  // fTemplateFile           = pset.get< std::string >("TemplateFile");
  // //fCalorimetryModuleLabel = pset.get< std::string >("CalorimetryModuleLabel");

   cet::search_path sp("FW_SEARCH_PATH");
   std::string fROOTfile; //return /lbne/data/0-100-1.57.root
   if( sp.find_file(tmpfileName, fROOTfile) ) fileName = fROOTfile;

   std::cout << "File path; " << fileName << std::endl;

    if(fSetRead){
      struct stat buffer;
      fSetRead = stat(fileName.c_str(), &buffer) == 0; // Check if file exists already
      if(!fSetRead) std::cout << "WARNING- "+fileName+" does not exist." << std::endl;
      else{
        std::cout << "Reading PDF from file "+fileName << std::endl;
        m_File = new TFile(fileName.c_str()); // Open file
        if(m_File->IsZombie() || m_File->TestBit(TFile::kRecovered)){ // Check that file is not corrupted
          std::cout << "WARNING- "+fileName+" is corrupted or cannot be read." << std::endl;
          fSetRead = false;
        }
      }
    }

    if(fSetRead){ // If the file exists then read it....
      std::cout << "Now going to read file...." << std::endl;
      fSetWrite = false; // Don't want to write as already exists
      double thetalow  = fThetamin;
      m_thetaHist = (TH1D*) m_File->Get("pdf_theta");
      for(int i=1; i<=fThetaBins; i++){
        std::ostringstream pdfEnergyHist;
        pdfEnergyHist << "pdf_energy_"<<i;
        std::string pdfEnergyHiststr = pdfEnergyHist.str();

        TH1* pdf_hist = (TH1D*) m_File->Get( pdfEnergyHiststr.c_str() ); // Get the bin
        m_PDFmap->insert(std::make_pair(-thetalow,pdf_hist));         //---- -ve theta for quicker sorting
        thetalow = double(i)*(fThetamax)/double(fThetaBins); //---- increment the value of theta
      }
    }      // ------------------------------------------
    else { // File doesn't exist so want to make it.....
           // ------------------------------------------
      std::cout << "Generating a new muon flux PDF" << std::endl;
      if(fSetWrite){
        std::cout << "Writing to PDF to file "+fileName << std::endl;
        m_File = new TFile(fileName.c_str(),"RECREATE");
      }

      double dnbins_theta = double(fThetaBins);
      m_thetaHist = new TH1D("pdf_theta", "pdf_theta", fThetaBins, fThetamin, fThetamax);
      for(int i=1; i<=fThetaBins; i++){
        double di = i==0 ? 0.1 : double(i);
        double theta = di*(fThetamax)/dnbins_theta;
        double int_i = muonSpec->Integral(fEmin, fEmax, fThetamin, theta, fEpsilon);
        m_thetaHist->SetBinContent(i, int_i/TotalMuonFlux);
      }
      if(fSetWrite) m_thetaHist->Write();
      std::cout << "theta PDF complete... now making the energy PDFs (this will take a little longer)... " << std::endl;

      //---- now compute the energy pdf
      double thetalow  = fThetamin;
      for(int i=1; i<=fThetaBins; i++){

        double di = double(i);
        double theta = di*(fThetamax)/fThetaBins;

        //---- compute the total integral
        double int_tot = muonSpec->Integral(fEmin, fEmax, thetalow, theta, fEpsilon);

        //---- compute pdf for the low energy
        int nbins = fEBinsLow;
        TH1* pdf_lowenergy = new TH1D("pdf_lowenergy", "pdf_lowenergy", nbins, fEmin, fEmid);
        double dnbins = double(nbins);
        for(int j=1; j<=nbins; j++){
          double dj = double(j);
          double int_j = muonSpec->Integral(fEmin, fEmin + dj*(fEmid-fEmin)/dnbins, thetalow, theta, fEpsilon);
          //    std::std::cout << j << "(" << m_emin << " --> " << m_emin + dj*m_emid/dnbins << ") = " << int_j/int_tot << std::std::endl;
          //    std::std::cout << j << "(" << m_emin << " --> " << m_emin + dj*(m_emid-m_emin)/dnbins << ") = " << int_j/int_tot << std::std::endl;
          pdf_lowenergy->SetBinContent(j, int_j/int_tot);
        }

        //---- compute pdf for the high energy
        nbins = fEBinsHigh;
        dnbins=double(nbins);
        TH1* pdf_highenergy = new TH1D("pdf_highenergy", "pdf_highenergy", nbins, fEmid, fEmax);
        for(int j=1; j<=nbins; j++){
          double dj = double(j);
          double int_j = muonSpec->Integral(fEmin, fEmid + dj*(fEmax-fEmid)/dnbins, thetalow, theta, fEpsilon);
          //      std::cout << j << "(" << m_emin << " --> " << m_emid + dj*(m_emax-m_emid)/dnbins << ") = " << int_j/int_tot << std::endl;
          pdf_highenergy->SetBinContent(j, int_j/int_tot);
        }

        //---- now combine the two energy hists
        std::vector<double> vxbins  = GetBinning(pdf_lowenergy->GetXaxis(),false);
        std::vector<double> vxbins2 = GetBinning(pdf_highenergy->GetXaxis());
        vxbins.insert(vxbins.end(), vxbins2.begin(), vxbins2.end());

        int ibin = 0;
        double* xbins = new double[vxbins.size()];
        for(std::vector<double>::const_iterator binit=vxbins.begin(); binit!=vxbins.end(); binit++, ibin++) xbins[ibin]=(*binit);
        TH1* pdf_energy = new TH1D("pdf_energy", "pdf_energy", vxbins.size()-1, xbins);
        int ibin2 = 1;
        for(ibin = 1; ibin<=pdf_lowenergy->GetNbinsX();   ibin++, ibin2++){
          double content = pdf_lowenergy->GetBinContent(ibin);
          if(ibin == 1) content = content - 0.00001;
          pdf_energy->Fill(pdf_energy->GetBinCenter(ibin2), content);
        }
        for(ibin = 1; ibin<=pdf_highenergy->GetNbinsX();  ibin++, ibin2++){
          pdf_energy->Fill(pdf_energy->GetBinCenter(ibin2), pdf_highenergy->GetBinContent(ibin));
        }

        //---- and remove any negative bins
        std::ostringstream Clonestr;
        Clonestr << "pdf_energy_"<<i;
        TH1* pdf_energy_noneg = (TH1D*) pdf_energy->Clone( Clonestr.str().c_str() );
        pdf_energy_noneg->Reset();

        double PDF = 0.0;
        double lastPD = 0.0;
        int nSkip=0;
        for(ibin = 1; ibin<=pdf_energy->GetNbinsX(); ibin++){
          double newPD    = pdf_energy->GetBinContent(ibin);
          double probDiff = newPD - lastPD;
          if(probDiff<0){
            if(ibin!=pdf_energy->GetNbinsX()){
              nSkip++;
              continue;
            }
            else probDiff = 0;
          }
          else PDF += probDiff;
          if(PDF > 1) PDF = 1;
          for(int iskip=0; iskip <= nSkip; iskip++) pdf_energy_noneg->Fill(pdf_energy_noneg->GetBinCenter(ibin-iskip), PDF);
          nSkip=0;
          lastPD = newPD;
        }


        //---- add this hist, increment thetalow and delete unwanted TH1s
        if(fSetWrite) pdf_energy_noneg->Write();
        m_PDFmap->insert(std::make_pair(-thetalow,pdf_energy_noneg)); //---- -ve theta for quicker sorting

        //---- increment the value of theta
        thetalow = theta;

        //---- free up memory from unwanted hists
        delete pdf_lowenergy;
        delete pdf_highenergy;
        delete pdf_energy;

        std::cout << "\r===> " << 100.0*double(i)/double(fThetaBins) << "% complete... " << std::endl;
      } // ThetaBins
      std::cout << "finished the energy pdfs." << std::endl;
    }//---- if(!m_doRead)

    delete muonSpec;
    return;
  } // Make PDF

  //_____________________________________________________________________________
  double GaisserParam::GaisserFlux(double e, double theta){

    double ct  = cos(theta);
    double di;
    if(fSetParam){
      //    double gamma=2.77;   // LVD spectrum: spectral index
      //    double A=1.84*0.14;  // normalisation
      double gamma = 2.7;
      double A = 0.14;
      double rc = 1.e-4;   // fraction of prompt muons
      double c1  = sqrt(1.-(1.-pow(ct,2.0))/pow( (1.+32./6370.) ,2.0));  // Earth curvature
      double deltae = 2.06e-3 * (1030. / c1 - 120.);         // muon energy loss in atmosphere
      double em = e + deltae/2.;
      double e1 = e + deltae;
      double pdec = pow( (120. / (1030. / c1)), (1.04 / c1 / em));   // muon decay
      di=A*pow(e1,-gamma)*(1./(1.+1.1*e1*c1/115.) + 0.054/(1.+1.1*e1*c1/850.) + rc)*pdec;
    }
    else{
      double gamma=2.7; // spectral index
      double A=0.14;    // normalisation
      double C = 3.64;
      double gamma2 = 1.29;
      double ct_star = sqrt( (pow(ct,2) + 0.102573*0.102573 - 0.068287*pow(ct,0.958633)
                              + 0.0407253*pow(ct,0.817285) )/(1.0 + 0.102573*0.102573 - 0.068287 + 0.0407253) );
      double eMod = e*(1.0+C/(e*pow(ct_star,gamma2)));
      di=A*pow(eMod,-gamma)*(1./(1.+1.1*e*ct_star/115.) + 0.054/(1.+1.1*e*ct_star/850.));
    }

    return di;
  } // GaisserFlux

  //______________________________________________________________________________
  double GaisserParam::GaisserMuonFlux_Integrand(Double_t *x, Double_t*){

    //---- calculate the flux
    double flux = 2.0*M_PI*sin(x[1])*GaisserFlux(x[0],x[1]);

    return flux;
  } // MuonFluxIntegrand

  //__________________________________
  std::vector<double> GaisserParam::GetBinning(const TAxis* axis, bool finalEdge){
    std::vector<double> vbins;
    for(int ibin=1; ibin<=axis->GetNbins()+1; ibin++){
      if(ibin<=axis->GetNbins()) vbins.push_back(axis->GetBinLowEdge(ibin));
      else if(finalEdge) vbins.push_back(axis->GetBinLowEdge(ibin) + axis->GetBinWidth(ibin));
    }
    return vbins;
  } // Get Binning

  //__________________________________
  void GaisserParam::ResetMap(){
    if(m_thetaHist) delete m_thetaHist;
    if(m_PDFmap){
      for(dhist_Map_it mapit=m_PDFmap->begin(); mapit!=m_PDFmap->end(); mapit++){
        if(mapit->second) delete mapit->second;
      }
      m_PDFmap->clear();
      delete m_PDFmap;
      std::cout << "Reset PDFmap and thetaHist..." << std::endl;
    }
  } // ResetMap

}//end namespace evgen

DEFINE_ART_MODULE(evgen::GaisserParam)