TParticle.cxx

Go to the documentation of this file.

// @(#)root/eg:$Id$
// Author: Rene Brun , Federico Carminati  26/04/99

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

/** \class  TParticle
    \ingroup eg

Description of the dynamic properties of a particle.

A dynamic particle class created by event generators and used during
the propagation in detectors. The static attributes of a TParticle
are described by TParticlePDG.

\verbatim
 Int_t          fPdgCode;              // PDG code of the particle
 Int_t          fStatusCode;           // generation status code
 Int_t          fMother[2];            // Indices of the mother particles
 Int_t          fDaughter[2];          // Indices of the daughter particles
 Float_t        fWeight;               // particle weight

 Double_t       fCalcMass;             // Calculated mass

 Double_t       fPx;                   // x component of momentum
 Double_t       fPy;                   // y component of momentum
 Double_t       fPz;                   // z component of momentum
 Double_t       fE;                    // Energy

 Double_t       fVx;                   // x of production vertex
 Double_t       fVy;                   // y of production vertex
 Double_t       fVz;                   // z of production vertex
 Double_t       fVt;                   // t of production vertex

 Double_t       fPolarTheta;           // Polar angle of polarisation
 Double_t       fPolarPhi;             // azymutal angle of polarisation

 TParticlePDG*  fParticlePDG;          //! reference to the particle record in PDG database
\endverbatim
*/

#include "TParticle.h"

#include "TBuffer.h"
#include "TView.h"
#include "TVirtualPad.h"
#include "TPolyLine3D.h"
#include "TParticlePDG.h"
#include "TDatabasePDG.h"
#include "TClass.h"
#include "X3DBuffer.h"

ClassImp(TParticle);

////////////////////////////////////////////////////////////////////////////////
///default constructor

TParticle::TParticle() :
  fPdgCode(0), fStatusCode(0), fWeight(0),fCalcMass(0), fPx(0), fPy(0),
  fPz(0), fE(0), fVx(0), fVy(0), fVz(0), fVt(0), fPolarTheta(0), fPolarPhi(0)
{
   fMother[0]   = 0;
   fMother[1]   = 0;
   fDaughter[0] = 0;
   fDaughter[1] = 0;
   fParticlePDG = 0;
}

////////////////////////////////////////////////////////////////////////////////
///constructor

TParticle::TParticle(Int_t pdg,       Int_t status,
                     Int_t mother1,   Int_t mother2,
                     Int_t daughter1, Int_t daughter2,
                     Double_t px, Double_t py, Double_t pz, Double_t etot,
                     Double_t vx, Double_t vy, Double_t vz, Double_t time):
  fPdgCode(pdg), fStatusCode(status), fWeight(1.),fPx(px), fPy(py),
  fPz(pz), fE(etot), fVx(vx), fVy(vy), fVz(vz), fVt(time)
{
   fMother[0]   = mother1;
   fMother[1]   = mother2;
   fDaughter[0] = daughter1;
   fDaughter[1] = daughter2;

   SetPolarisation(0,0,0);

   SetPdgCode(pdg);
}

////////////////////////////////////////////////////////////////////////////////
///constructor

TParticle::TParticle(Int_t pdg,       Int_t status,
                     Int_t mother1,   Int_t mother2,
                     Int_t daughter1, Int_t daughter2,
                     const TLorentzVector &p,
                     const TLorentzVector &v) :
  fPdgCode(pdg), fStatusCode(status), fWeight(1.),fPx(p.Px()), fPy(p.Py()),
  fPz(p.Pz()), fE(p.E()), fVx(v.X()), fVy(v.Y()), fVz(v.Z()), fVt(v.T())
{
   fMother[0]   = mother1;
   fMother[1]   = mother2;
   fDaughter[0] = daughter1;
   fDaughter[1] = daughter2;

   SetPolarisation(0,0,0);

   SetPdgCode(pdg);
}

////////////////////////////////////////////////////////////////////////////////
/// copy constructor

TParticle::TParticle(const TParticle &p) :
  TObject(p), TAttLine(p), TAtt3D(p), fPdgCode(p.fPdgCode), fStatusCode(p.fStatusCode),
  fWeight(p.fWeight), fCalcMass(p.fCalcMass), fPx(p.fPx), fPy(p.fPy), fPz(p.fPz),
  fE(p.fE), fVx(p.fVx), fVy(p.fVy), fVz(p.fVz), fVt(p.fVt), fPolarTheta(p.fPolarTheta),
  fPolarPhi(p.fPolarPhi), fParticlePDG(p.fParticlePDG)
{
   fMother[0]=p.fMother[0];
   fMother[1]=p.fMother[1];
   fDaughter[0]=p.fDaughter[0];
   fDaughter[1]=p.fDaughter[1];
}

////////////////////////////////////////////////////////////////////////////////
/// Equal operator

TParticle& TParticle::operator=(const TParticle &p)
{
   if(this!=&p) {
      TObject::operator=(p);
      TAttLine::operator=(p);
      TAtt3D::operator=(p);
      fPdgCode=p.fPdgCode;
      fStatusCode=p.fStatusCode;
      fMother[0]=p.fMother[0];
      fMother[1]=p.fMother[1];
      fDaughter[0]=p.fDaughter[0];
      fDaughter[1]=p.fDaughter[1];
      fWeight=p.fWeight;

      fCalcMass=p.fCalcMass;

      fPx=p.fPx;
      fPy=p.fPy;
      fPz=p.fPz;
      fE=p.fE;

      fVx=p.fVx;
      fVy=p.fVy;
      fVz=p.fVz;
      fVt=p.fVt;

      fPolarTheta=p.fPolarTheta;
      fPolarPhi=p.fPolarPhi;

      fParticlePDG=p.fParticlePDG;
   }
   return   *this;
}

////////////////////////////////////////////////////////////////////////////////
///destructor

TParticle::~TParticle()
{
}

////////////////////////////////////////////////////////////////////////////////
/// Return nominal particle mass from PDG table.

Double_t TParticle::GetMass() const
{
   return GetPDG()->Mass();
}

////////////////////////////////////////////////////////////////////////////////
/// Return beauty quantum number.

Int_t TParticle::Beauty() const
{
   return GetPDG()->Beauty();
}

////////////////////////////////////////////////////////////////////////////////
/// Return charm quantum number.

Int_t TParticle::Charm() const
{
   return GetPDG()->Charm();
}

////////////////////////////////////////////////////////////////////////////////
/// Return strangeness quantum number.

Int_t TParticle::Strangeness() const
{
   return GetPDG()->Strangeness();
}

////////////////////////////////////////////////////////////////////////////////
/// Compute distance from point px,py to a primary track
///
/// Compute the closest distance of approach from point px,py to each segment
/// of a track.
/// The distance is computed in pixels units.
///ß

Int_t TParticle::DistancetoPrimitive(Int_t px, Int_t py)
{
   const Int_t big = 9999;
   Float_t xv[3], xe[3], xndc[3];
   Float_t rmin[3], rmax[3];
   TView *view = gPad->GetView();
   if(!view) return big;

   // compute first and last point in pad coordinates
   Float_t pmom = this->P();
   if (pmom == 0) return big;
   view->GetRange(rmin,rmax);
   Float_t rbox = rmax[2];
   xv[0] = fVx;
   xv[1] = fVy;
   xv[2] = fVz;
   xe[0] = xv[0]+rbox*fPx/pmom;
   xe[1] = xv[1]+rbox*fPy/pmom;
   xe[2] = xv[2]+rbox*fPz/pmom;
   view->WCtoNDC(xv, xndc);
   Float_t x1 = xndc[0];
   Float_t y1 = xndc[1];
   view->WCtoNDC(xe, xndc);
   Float_t x2 = xndc[0];
   Float_t y2 = xndc[1];

   return DistancetoLine(px,py,x1,y1,x2,y2);
}


////////////////////////////////////////////////////////////////////////////////
/// Execute action corresponding to one event
///

void TParticle::ExecuteEvent(Int_t, Int_t, Int_t)
{
   gPad->SetCursor(kPointer);
}

////////////////////////////////////////////////////////////////////////////////
/// Return particle name

const char* TParticle::GetName() const {
   static char def[4] = "XXX";
   const TParticlePDG *ap = TDatabasePDG::Instance()->GetParticle(fPdgCode);
   if (ap) return ap->GetName();
   else    return def;
}


////////////////////////////////////////////////////////////////////////////////
/// Returns a pointer to the TParticlePDG object using the pdgcode.
/// - if mode == 0 (default) always get a fresh value for the pointer.
/// - if mode != 0 this function returns directly the previously
///              computed pointer from a previous call
/// One can use mode=1 (faster) when the TParticle object is not part of a
/// TClonesArray used in split mode in a Root TTree.

TParticlePDG*  TParticle::GetPDG(Int_t mode) const
{
   if (!mode || !fParticlePDG) {
      fParticlePDG = TDatabasePDG::Instance()->GetParticle(fPdgCode);
   }
   return fParticlePDG;
}

////////////////////////////////////////////////////////////////////////////////
/// Return particle polarisation

void TParticle::GetPolarisation(TVector3 &v) const
{
   if(fPolarTheta == -99 && fPolarPhi == -99)
      //No polarisation to return
      v.SetXYZ(0.,0.,0.);
   else
      v.SetXYZ(TMath::Cos(fPolarPhi)*TMath::Sin(fPolarTheta),
               TMath::Sin(fPolarPhi)*TMath::Sin(fPolarTheta),
               TMath::Cos(fPolarTheta));
}

////////////////////////////////////////////////////////////////////////////////
/// Return particle title

const char *TParticle::GetTitle() const
{
   static char def[4] = "XXX";
   const TParticlePDG *ap = TDatabasePDG::Instance()->GetParticle(fPdgCode);
   if (ap) return ap->GetTitle();
   else    return def;
}

////////////////////////////////////////////////////////////////////////////////
///
///  Paint a primary track
///

void TParticle::Paint(Option_t *option)
{
   Float_t rmin[3], rmax[3];
   static TPolyLine3D *pline = 0;
   if (!pline) {
      pline = new TPolyLine3D(2);
   }
   Float_t pmom = this->P();
   if (pmom == 0) return;
   TView *view = gPad->GetView();
   if (!view) return;
   view->GetRange(rmin,rmax);
   Float_t rbox = rmax[2];
   pline->SetPoint(0,Vx(), Vy(), Vz());
   Float_t xend = Vx()+rbox*Px()/pmom;
   Float_t yend = Vy()+rbox*Py()/pmom;
   Float_t zend = Vz()+rbox*Pz()/pmom;
   pline->SetPoint(1, xend, yend, zend);
   pline->SetLineColor(GetLineColor());
   pline->SetLineStyle(GetLineStyle());
   pline->SetLineWidth(GetLineWidth());
   pline->Paint(option);
}

////////////////////////////////////////////////////////////////////////////////
///
///  Print the internals of the primary vertex particle
///

void TParticle::Print(Option_t *) const
{
   Printf("TParticle: %-13s  p: %8f %8f %8f Vertex: %8e %8e %8e %5d %5d",
          GetName(),Px(),Py(),Pz(),Vx(),Vy(),Vz(),
          fMother[0],fMother[1]);
}

////////////////////////////////////////////////////////////////////////////////
/// Change the PDG code for this particle
///
/// Get a new pointer to a TParticlePDG from TDatabasePDG.
/// Recompute the mass.

void TParticle::SetPdgCode(Int_t pdg)
{
   static Int_t nWarnings = 0;
   fPdgCode = pdg;
   fParticlePDG = TDatabasePDG::Instance()->GetParticle(pdg);
   if (fParticlePDG) {
      fCalcMass    = fParticlePDG->Mass();
   } else {
      if (nWarnings < 10) {
         Warning("SetPdgCode","PDG code %d unknown from TDatabasePDG",pdg);
         nWarnings++;
      }
      Double_t a2 = fE*fE -fPx*fPx -fPy*fPy -fPz*fPz;
      if (a2 >= 0) fCalcMass =  TMath::Sqrt(a2);
      else         fCalcMass = -TMath::Sqrt(-a2);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set particle polarisation

void TParticle::SetPolarisation(Double_t polx, Double_t poly, Double_t polz)
{
   if(polx || poly || polz) {
      fPolarTheta = TMath::ACos(polz/TMath::Sqrt(polx*polx+poly*poly+polz*polz));
      fPolarPhi   = TMath::Pi()+TMath::ATan2(-poly,-polx);
   } else {
      fPolarTheta = -99;
      fPolarPhi = -99;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Return total X3D size of this primary
///

void TParticle::Sizeof3D() const
{
   Float_t pmom = this->P();
   if (pmom == 0) return;
   Int_t npoints = 2;
   gSize3D.numPoints += npoints;
   gSize3D.numSegs   += (npoints-1);
   gSize3D.numPolys  += 0;

}

////////////////////////////////////////////////////////////////////////////////
/// Stream an object of class TParticle.

void TParticle::Streamer(TBuffer &R__b)
{
   if (R__b.IsReading()) {
      UInt_t R__s, R__c;
      Version_t R__v = R__b.ReadVersion(&R__s, &R__c);
      if (R__v > 1) {
         R__b.ReadClassBuffer(TParticle::Class(), this, R__v, R__s, R__c);
         fParticlePDG = TDatabasePDG::Instance()->GetParticle(fPdgCode);
         return;
      }
      //====process old versions before automatic schema evolution
      TObject::Streamer(R__b);
      TAttLine::Streamer(R__b);
      R__b >> fPdgCode;
      R__b >> fStatusCode;
      R__b.ReadStaticArray(fMother);
      R__b.ReadStaticArray(fDaughter);
      R__b >> fWeight;
      R__b >> fCalcMass;
      R__b >> fPx;
      R__b >> fPy;
      R__b >> fPz;
      R__b >> fE;
      R__b >> fVx;
      R__b >> fVy;
      R__b >> fVz;
      R__b >> fVt;
      R__b >> fPolarTheta;
      R__b >> fPolarPhi;
      fParticlePDG = TDatabasePDG::Instance()->GetParticle(fPdgCode);
      R__b.CheckByteCount(R__s, R__c, TParticle::IsA());
      //====end of old versions

   } else {
      R__b.WriteClassBuffer(TParticle::Class(),this);
   }
}