/************************************************************************** * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * * * * Author: The ALICE Off-line Project. * * Contributors are mentioned in the code where appropriate. * * * * Permission to use, copy, modify and distribute this software and its * * documentation strictly for non-commercial purposes is hereby granted * * without fee, provided that the above copyright notice appears in all * * copies and that both the copyright notice and this permission notice * * appear in the supporting documentation. The authors make no claims * * about the suitability of this software for any purpose. It is * * provided "as is" without express or implied warranty. * **************************************************************************/ //------------------------------------------------------------------------- // Implementation of the V0 vertex class // // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch //------------------------------------------------------------------------- #include #include #include "AliV0vertex.h" #include "AliITStrackV2.h" ClassImp(AliV0vertex) AliV0vertex::AliV0vertex() : TObject() { //-------------------------------------------------------------------- // Default constructor (K0s) //-------------------------------------------------------------------- fPdgCode=kK0Short; fEffMass=0.497672; fChi2=1.e+33; fPos[0]=fPos[1]=fPos[2]=0.; fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.; } AliV0vertex::AliV0vertex(const AliITStrackV2 &n, const AliITStrackV2 &p) { //-------------------------------------------------------------------- // Main constructor //-------------------------------------------------------------------- fPdgCode=kK0Short; fNlab=n.GetLabel(); fPlab=p.GetLabel(); //Trivial estimation of the vertex parameters Double_t pt, phi, x, par[5]; Double_t alpha, cs, sn; n.GetExternalParameters(x,par); alpha=n.GetAlpha(); pt=1./TMath::Abs(par[4]); phi=TMath::ASin(par[2]) + alpha; Double_t px1=pt*TMath::Cos(phi), py1=pt*TMath::Sin(phi), pz1=pt*par[3]; cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); Double_t x1=x*cs - par[0]*sn; Double_t y1=x*sn + par[0]*cs; Double_t z1=par[1]; Double_t sx1=sn*sn*n.GetSigmaY2(), sy1=cs*cs*n.GetSigmaY2(); p.GetExternalParameters(x,par); alpha=p.GetAlpha(); pt=1./TMath::Abs(par[4]); phi=TMath::ASin(par[2]) + alpha; Double_t px2=pt*TMath::Cos(phi), py2=pt*TMath::Sin(phi), pz2=pt*par[3]; cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); Double_t x2=x*cs - par[0]*sn; Double_t y2=x*sn + par[0]*cs; Double_t z2=par[1]; Double_t sx2=sn*sn*p.GetSigmaY2(), sy2=cs*cs*p.GetSigmaY2(); Double_t sz1=n.GetSigmaZ2(), sz2=p.GetSigmaZ2(); Double_t wx1=sx2/(sx1+sx2), wx2=1.- wx1; Double_t wy1=sy2/(sy1+sy2), wy2=1.- wy1; Double_t wz1=sz2/(sz1+sz2), wz2=1.- wz1; fPos[0]=wx1*x1 + wx2*x2; fPos[1]=wy1*y1 + wy2*y2; fPos[2]=wz1*z1 + wz2*z2; //fPos[0]=0.5*(x1+x2); fPos[1]=0.5*(y1+y2); fPos[2]=0.5*(z1+z2); fNmom[0]=px1; fNmom[1]=py1; fNmom[2]=pz1; fPmom[0]=px2; fPmom[1]=py2; fPmom[2]=pz2; Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1); Double_t e2=TMath::Sqrt(0.13957*0.13957 + px2*px2 + py2*py2 + pz2*pz2); fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)- (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2)); fChi2=7.; } /* Double_t AliV0vertex::ChangeMassHypothesis(Int_t code) { //-------------------------------------------------------------------- // This function changes the mass hypothesis for this V0 // and returns the "kinematical quality" of this hypothesis //-------------------------------------------------------------------- Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, des=0; fPdgCode=code; switch (code) { case kLambda0: nmass=0.13957; pmass=0.93827; mass=1.1157; des=0.9437-0.1723; break; case kLambda0Bar: pmass=0.13957; nmass=0.93827; mass=1.1157; des=0.1723-0.9437; break; case kK0Short: break; default: cerr<<"AliV0vertex::ChangeMassHypothesis: "; cerr<<"invalide PDG code ! Assuming K0s...\n"; fPdgCode=kK0Short; break; } Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2]; Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2]; Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn); Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp); Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp; Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl); Double_t gamma=(en+ep)/mass, betagamma=pl/mass; Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl; Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl; Double_t plps=gamma*plp - betagamma*ep; Double_t diff=2*gamma*plps + betagamma*des; return (plp-pln-diff); } */ Double_t AliV0vertex::ChangeMassHypothesis(Int_t code) { //-------------------------------------------------------------------- // This function changes the mass hypothesis for this V0 // and returns the "kinematical quality" of this hypothesis //-------------------------------------------------------------------- Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, ps=0.206; fPdgCode=code; switch (code) { case kLambda0: nmass=0.13957; pmass=0.93827; mass=1.1157; ps=0.101; break; case kLambda0Bar: pmass=0.13957; nmass=0.93827; mass=1.1157; ps=0.101; break; case kK0Short: break; default: cerr<<"AliV0vertex::ChangeMassHypothesis: "; cerr<<"invalide PDG code ! Assuming K0s...\n"; fPdgCode=kK0Short; break; } Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2]; Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2]; Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn); Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp); Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp; Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl); Double_t beta=pl/(en+ep); Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl; Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl; Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; Double_t a=(plp-pln)/(plp+pln); a -= (pmass*pmass-nmass*nmass)/(mass*mass); a = 0.25*beta*beta*mass*mass*a*a + pt2; return (a - ps*ps); } void AliV0vertex::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { //-------------------------------------------------------------------- // This function returns V0's momentum (global) //-------------------------------------------------------------------- px=fNmom[0]+fPmom[0]; py=fNmom[1]+fPmom[1]; pz=fNmom[2]+fPmom[2]; } void AliV0vertex::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { //-------------------------------------------------------------------- // This function returns V0's position (global) //-------------------------------------------------------------------- x=fPos[0]; y=fPos[1]; z=fPos[2]; } Double_t AliV0vertex::GetD(Double_t x0, Double_t y0, Double_t z0) const { //-------------------------------------------------------------------- // This function returns V0's impact parameter //-------------------------------------------------------------------- Double_t x=fPos[0],y=fPos[1],z=fPos[2]; Double_t px=fNmom[0]+fPmom[0]; Double_t py=fNmom[1]+fPmom[1]; Double_t pz=fNmom[2]+fPmom[2]; Double_t dx=(y0-y)*pz - (z0-z)*py; Double_t dy=(x0-x)*pz - (z0-z)*px; Double_t dz=(x0-x)*py - (y0-y)*px; Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); return d; }