/************************************************************************** * 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 cascade vertex class // // Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr //------------------------------------------------------------------------- #include #include #include "AliCascadeVertex.h" #include "AliV0vertex.h" #include "AliITStrackV2.h" ClassImp(AliCascadeVertex) AliCascadeVertex::AliCascadeVertex() : TObject() { //-------------------------------------------------------------------- // Default constructor (Xi-) //-------------------------------------------------------------------- fPdgCode=kXiMinus; fEffMass=1.32131; fChi2=1.e+33; fPos[0]=fPos[1]=fPos[2]=0.; fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.; } inline Double_t det(Double_t a00, Double_t a01, Double_t a10, Double_t a11){ // determinant 2x2 return a00*a11 - a01*a10; } inline Double_t det (Double_t a00,Double_t a01,Double_t a02, Double_t a10,Double_t a11,Double_t a12, Double_t a20,Double_t a21,Double_t a22) { // determinant 3x3 return a00*det(a11,a12,a21,a22)-a01*det(a10,a12,a20,a22)+a02*det(a10,a11,a20,a21); } AliCascadeVertex::AliCascadeVertex(const AliV0vertex &v,const AliITStrackV2 &t) { //-------------------------------------------------------------------- // Main constructor //-------------------------------------------------------------------- fPdgCode=kXiMinus; fV0lab[0]=v.GetNlabel(); fV0lab[1]=v.GetPlabel(); fBachLab=t.GetLabel(); //Trivial estimation of the vertex parameters Double_t pt, phi, x, par[5]; Double_t alpha, cs, sn; t.GetExternalParameters(x,par); alpha=t.GetAlpha(); pt=1./TMath::Abs(par[4]); phi=TMath::ASin(par[2]) + alpha; // momentum of the bachelor track 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; // position of the bachelor at dca (bachelor,V0) Double_t y1=x*sn + par[0]*cs; Double_t z1=par[1]; Double_t x2,y2,z2; // position of the V0 v.GetXYZ(x2,y2,z2); Double_t px2,py2,pz2; // momentum of V0 v.GetPxPyPz(px2,py2,pz2); Double_t a2=((x1-x2)*px2+(y1-y2)*py2+(z1-z2)*pz2)/(px2*px2+py2*py2+pz2*pz2); Double_t xm=x2+a2*px2; Double_t ym=y2+a2*py2; Double_t zm=z2+a2*pz2; // position of the cascade decay fPos[0]=0.5*(x1+xm); fPos[1]=0.5*(y1+ym); fPos[2]=0.5*(z1+zm); // invariant mass of the cascade (default is Ximinus) Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1); Double_t e2=TMath::Sqrt(1.11568*1.11568 + 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)); // momenta of the bachelor and the V0 fBachMom[0]=px1; fBachMom[1]=py1; fBachMom[2]=pz1; v.GetNPxPyPz(px2,py2,pz2); fV0mom[0][0]=px2; fV0mom[0][1]=py2; fV0mom[0][2]=pz2; v.GetPPxPyPz(px2,py2,pz2); fV0mom[1][0]=px2; fV0mom[1][1]=py2; fV0mom[1][2]=pz2; fChi2=7.; } /* Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) { //-------------------------------------------------------------------- // This function changes the mass hypothesis for this cascade // and returns the "kinematical quality" of this hypothesis // together with the "quality" of associated V0 (argument v0q) //-------------------------------------------------------------------- Double_t nmass=0.13957, pmass=0.93827, des0=0.9437-0.1723; Double_t bmass=0.13957, mass =1.3213, des =1.1243-0.1970; fPdgCode=code; switch (code) { case 213: bmass=0.93827; break; case kXiMinus: break; case kXiPlusBar: nmass=0.93827; pmass=0.13957; des0=-des0; des=-des; break; case kOmegaMinus: bmass=0.49368; mass=1.67245; des=1.1355-0.5369; break; case kOmegaPlusBar: nmass=0.93827; pmass=0.13957; des0=-des0; bmass=0.49368; mass=1.67245; des=0.5369-1.1355; break; default: cerr<<"AliCascadeVertex::ChangeMassHypothesis: "; cerr<<"Invalide PDG code ! Assuming XiMinus's...\n"; fPdgCode=kXiMinus; break; } Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2]; Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][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 px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp; Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0); Double_t gamma0=(en+ep)/1.11568, betagamma0=p0/1.11568; Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0; Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0; Double_t plps=gamma0*plp - betagamma0*ep; Double_t diff0=2*gamma0*plps + betagamma0*des0; v0q=plp-pln-diff0; Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2]; Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0); Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb); Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb; Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl); Double_t gamma=(e0+eb)/mass, betagamma=pl/mass; Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl; Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl; Double_t pl0s=gamma*pl0 - betagamma*e0; Double_t diff=2*gamma*pl0s + betagamma*des; return (pl0-plb-diff); } */ Double_t AliCascadeVertex::ChangeMassHypothesis(Double_t &v0q, Int_t code) { //-------------------------------------------------------------------- // This function changes the mass hypothesis for this cascade // and returns the "kinematical quality" of this hypothesis // together with the "quality" of associated V0 (argument v0q) //-------------------------------------------------------------------- Double_t nmass=0.13957, pmass=0.93827, ps0=0.101; Double_t bmass=0.13957, mass =1.3213, ps =0.139; fPdgCode=code; switch (code) { case 213: bmass=0.93827; break; case kXiMinus: break; case kXiPlusBar: nmass=0.93827; pmass=0.13957; break; case kOmegaMinus: bmass=0.49368; mass=1.67245; ps=0.211; break; case kOmegaPlusBar: nmass=0.93827; pmass=0.13957; bmass=0.49368; mass=1.67245; ps=0.211; break; default: cerr<<"AliCascadeVertex::ChangeMassHypothesis: "; cerr<<"Invalide PDG code ! Assuming XiMinus's...\n"; fPdgCode=kXiMinus; break; } Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2]; Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2]; Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp; Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0); Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0); Double_t beta0=p0/e0; Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0; Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0; Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; Double_t a=(plp-pln)/(plp+pln); a -= (pmass*pmass-nmass*nmass)/(1.11568*1.11568); a = 0.25*beta0*beta0*1.11568*1.11568*a*a + pt2; v0q=a - ps0*ps0; Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2]; Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb); Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb; Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl); Double_t beta=pl/(e0+eb); Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl; Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl; pt2=p0*p0 - pl0*pl0; a=(pl0-plb)/(pl0+plb); a -= (1.11568*1.11568-bmass*bmass)/(mass*mass); a = 0.25*beta*beta*mass*mass*a*a + pt2; return (a - ps*ps); } void AliCascadeVertex::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { //-------------------------------------------------------------------- // This function returns the cascade momentum (global) //-------------------------------------------------------------------- px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0]; py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1]; pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2]; } void AliCascadeVertex::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { //-------------------------------------------------------------------- // This function returns cascade position (global) //-------------------------------------------------------------------- x=fPos[0]; y=fPos[1]; z=fPos[2]; } Double_t AliCascadeVertex::GetD(Double_t x0, Double_t y0, Double_t z0) const { //-------------------------------------------------------------------- // This function returns the cascade impact parameter //-------------------------------------------------------------------- Double_t x=fPos[0],y=fPos[1],z=fPos[2]; Double_t px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0]; Double_t py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1]; Double_t pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[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; }