1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
18 //-------------------------------------------------------------------------
19 // Implementation of the ESD V0 vertex class
20 // This class is part of the Event Data Summary
21 // set of classes and contains information about
22 // V0 kind vertexes generated by a neutral particle
23 // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch
24 //-------------------------------------------------------------------------
26 #include <Riostream.h>
28 #include <TDatabasePDG.h>
30 #include <TParticlePDG.h>
37 AliESDv0::AliESDv0() :
40 fEffMass(TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass()),
46 //--------------------------------------------------------------------
47 // Default constructor (K0s)
48 //--------------------------------------------------------------------
49 fPos[0]=fPos[1]=fPos[2]=0.;
50 fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.;
53 Double_t AliESDv0::ChangeMassHypothesis(Int_t code) {
54 //--------------------------------------------------------------------
55 // This function changes the mass hypothesis for this V0
56 // and returns the "kinematical quality" of this hypothesis
57 //--------------------------------------------------------------------
58 Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, ps=0.206;
64 nmass=0.13957; pmass=0.93827; mass=1.1157; ps=0.101; break;
66 pmass=0.13957; nmass=0.93827; mass=1.1157; ps=0.101; break;
70 AliError("invalide PDG code ! Assuming K0s...");
75 Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2];
76 Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2];
78 Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn);
79 Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp);
80 Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp;
81 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
83 fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl);
85 Double_t beta=pl/(en+ep);
86 Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl;
87 Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl;
89 Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp;
91 Double_t a=(plp-pln)/(plp+pln);
92 a -= (pmass*pmass-nmass*nmass)/(mass*mass);
93 a = 0.25*beta*beta*mass*mass*a*a + pt2;
99 void AliESDv0::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const {
100 //--------------------------------------------------------------------
101 // This function returns V0's momentum (global)
102 //--------------------------------------------------------------------
103 px=fNmom[0]+fPmom[0];
104 py=fNmom[1]+fPmom[1];
105 pz=fNmom[2]+fPmom[2];
108 void AliESDv0::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const {
109 //--------------------------------------------------------------------
110 // This function returns V0's position (global)
111 //--------------------------------------------------------------------
117 Double_t AliESDv0::GetD(Double_t x0, Double_t y0, Double_t z0) const {
118 //--------------------------------------------------------------------
119 // This function returns V0's impact parameter
120 //--------------------------------------------------------------------
121 Double_t x=fPos[0],y=fPos[1],z=fPos[2];
122 Double_t px=fNmom[0]+fPmom[0];
123 Double_t py=fNmom[1]+fPmom[1];
124 Double_t pz=fNmom[2]+fPmom[2];
126 Double_t dx=(y0-y)*pz - (z0-z)*py;
127 Double_t dy=(x0-x)*pz - (z0-z)*px;
128 Double_t dz=(x0-x)*py - (y0-y)*px;
129 Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz));