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e23730c7 | 1 | /************************************************************************** |
2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * | |
3 | * * | |
4 | * Author: The ALICE Off-line Project. * | |
5 | * Contributors are mentioned in the code where appropriate. * | |
6 | * * | |
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 | **************************************************************************/ | |
15 | ||
4f679a16 | 16 | /* $Id$ */ |
17 | ||
e23730c7 | 18 | //------------------------------------------------------------------------- |
19 | // Implementation of the ESD V0 vertex class | |
4f679a16 | 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 | |
e23730c7 | 23 | // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch |
24 | //------------------------------------------------------------------------- | |
4f679a16 | 25 | |
e23730c7 | 26 | #include <Riostream.h> |
27 | #include <TMath.h> | |
90e48c0c | 28 | #include <TDatabasePDG.h> |
e23730c7 | 29 | #include <TPDGCode.h> |
90e48c0c | 30 | #include <TParticlePDG.h> |
e23730c7 | 31 | |
5f7789fc | 32 | #include "AliLog.h" |
e23730c7 | 33 | #include "AliESDv0.h" |
c7bafca9 | 34 | #include "AliExternalTrackParam.h" |
e23730c7 | 35 | |
36 | ClassImp(AliESDv0) | |
37 | ||
90e48c0c | 38 | AliESDv0::AliESDv0() : |
39 | TObject(), | |
40 | fPdgCode(kK0Short), | |
41 | fEffMass(TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass()), | |
17f7744d | 42 | fDcaDaughters(0), |
90e48c0c | 43 | fChi2(1.e+33), |
44 | fNidx(0), | |
45 | fPidx(0) | |
46 | { | |
e23730c7 | 47 | //-------------------------------------------------------------------- |
48 | // Default constructor (K0s) | |
49 | //-------------------------------------------------------------------- | |
6605de26 | 50 | |
51 | for (Int_t i=0; i<3; i++) { | |
52 | fPos[i] = 0.; | |
53 | fNmom[i] = 0.; | |
54 | fPmom[i] = 0.; | |
55 | } | |
56 | ||
57 | for (Int_t i=0; i<6; i++) { | |
58 | fPosCov[i]= 0.; | |
59 | fNmomCov[i] = 0.; | |
60 | fPmomCov[i] = 0.; | |
61 | } | |
e23730c7 | 62 | } |
63 | ||
c7bafca9 | 64 | AliESDv0::AliESDv0(const AliExternalTrackParam &t1, Int_t i1, |
65 | const AliExternalTrackParam &t2, Int_t i2) : | |
66 | TObject(), | |
67 | fPdgCode(kK0Short), | |
68 | fEffMass(TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass()), | |
69 | fDcaDaughters(0), | |
70 | fChi2(1.e+33), | |
71 | fNidx(i1), | |
72 | fPidx(i2) | |
73 | { | |
74 | //-------------------------------------------------------------------- | |
75 | // Main constructor (K0s) | |
76 | //-------------------------------------------------------------------- | |
77 | ||
78 | for (Int_t i=0; i<6; i++) { | |
79 | fPosCov[i]= 0.; | |
80 | fNmomCov[i] = 0.; | |
81 | fPmomCov[i] = 0.; | |
82 | } | |
83 | ||
84 | //Trivial estimation of the vertex parameters | |
85 | Double_t x=t1.GetX(), alpha=t1.GetAlpha(); | |
86 | const Double_t *par=t1.GetParameter(); | |
87 | Double_t pt=1./TMath::Abs(par[4]), | |
88 | phi=TMath::ASin(par[2]) + alpha, | |
89 | cs=TMath::Cos(alpha), sn=TMath::Sin(alpha); | |
90 | ||
91 | Double_t px1=pt*TMath::Cos(phi), py1=pt*TMath::Sin(phi), pz1=pt*par[3]; | |
92 | Double_t x1=x*cs - par[0]*sn; | |
93 | Double_t y1=x*sn + par[0]*cs; | |
94 | Double_t z1=par[1]; | |
37919f0b | 95 | const Double_t ss=0.0005*0.0005;//a kind of a residual misalignment precision |
96 | Double_t sx1=sn*sn*t1.GetSigmaY2()+ss, sy1=cs*cs*t1.GetSigmaY2()+ss; | |
c7bafca9 | 97 | |
98 | ||
99 | ||
100 | x=t2.GetX(); alpha=t2.GetAlpha(); par=t2.GetParameter(); | |
101 | pt=1./TMath::Abs(par[4]); | |
102 | phi=TMath::ASin(par[2]) + alpha; | |
103 | cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); | |
104 | ||
105 | Double_t px2=pt*TMath::Cos(phi), py2=pt*TMath::Sin(phi), pz2=pt*par[3]; | |
106 | Double_t x2=x*cs - par[0]*sn; | |
107 | Double_t y2=x*sn + par[0]*cs; | |
108 | Double_t z2=par[1]; | |
37919f0b | 109 | Double_t sx2=sn*sn*t2.GetSigmaY2()+ss, sy2=cs*cs*t2.GetSigmaY2()+ss; |
c7bafca9 | 110 | |
111 | Double_t sz1=t1.GetSigmaZ2(), sz2=t2.GetSigmaZ2(); | |
37919f0b | 112 | Double_t wx1=sx2/(sx1+sx2), wx2=1.- wx1; |
113 | Double_t wy1=sy2/(sy1+sy2), wy2=1.- wy1; | |
c7bafca9 | 114 | Double_t wz1=sz2/(sz1+sz2), wz2=1.- wz1; |
115 | fPos[0]=wx1*x1 + wx2*x2; fPos[1]=wy1*y1 + wy2*y2; fPos[2]=wz1*z1 + wz2*z2; | |
116 | ||
117 | //fPos[0]=0.5*(x1+x2); fPos[1]=0.5*(y1+y2); fPos[2]=0.5*(z1+z2); | |
118 | fNmom[0]=px1; fNmom[1]=py1; fNmom[2]=pz1; | |
119 | fPmom[0]=px2; fPmom[1]=py2; fPmom[2]=pz2; | |
120 | ||
121 | Double_t e1=TMath::Sqrt(0.13957*0.13957 + px1*px1 + py1*py1 + pz1*pz1); | |
122 | Double_t e2=TMath::Sqrt(0.13957*0.13957 + px2*px2 + py2*py2 + pz2*pz2); | |
123 | fEffMass=TMath::Sqrt((e1+e2)*(e1+e2)- | |
124 | (px1+px2)*(px1+px2)-(py1+py2)*(py1+py2)-(pz1+pz2)*(pz1+pz2)); | |
125 | ||
126 | fChi2=7.; | |
127 | ||
128 | } | |
129 | ||
e23730c7 | 130 | Double_t AliESDv0::ChangeMassHypothesis(Int_t code) { |
131 | //-------------------------------------------------------------------- | |
132 | // This function changes the mass hypothesis for this V0 | |
133 | // and returns the "kinematical quality" of this hypothesis | |
134 | //-------------------------------------------------------------------- | |
135 | Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, ps=0.206; | |
136 | ||
137 | fPdgCode=code; | |
138 | ||
139 | switch (code) { | |
140 | case kLambda0: | |
141 | nmass=0.13957; pmass=0.93827; mass=1.1157; ps=0.101; break; | |
142 | case kLambda0Bar: | |
143 | pmass=0.13957; nmass=0.93827; mass=1.1157; ps=0.101; break; | |
144 | case kK0Short: | |
145 | break; | |
146 | default: | |
5f7789fc | 147 | AliError("invalide PDG code ! Assuming K0s..."); |
e23730c7 | 148 | fPdgCode=kK0Short; |
149 | break; | |
150 | } | |
151 | ||
152 | Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2]; | |
153 | Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2]; | |
154 | ||
155 | Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn); | |
156 | Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp); | |
157 | Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp; | |
158 | Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); | |
159 | ||
160 | fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl); | |
161 | ||
162 | Double_t beta=pl/(en+ep); | |
163 | Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl; | |
164 | Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl; | |
165 | ||
166 | Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; | |
167 | ||
168 | Double_t a=(plp-pln)/(plp+pln); | |
169 | a -= (pmass*pmass-nmass*nmass)/(mass*mass); | |
170 | a = 0.25*beta*beta*mass*mass*a*a + pt2; | |
171 | ||
172 | return (a - ps*ps); | |
173 | ||
174 | } | |
175 | ||
176 | void AliESDv0::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { | |
177 | //-------------------------------------------------------------------- | |
178 | // This function returns V0's momentum (global) | |
179 | //-------------------------------------------------------------------- | |
180 | px=fNmom[0]+fPmom[0]; | |
181 | py=fNmom[1]+fPmom[1]; | |
182 | pz=fNmom[2]+fPmom[2]; | |
183 | } | |
184 | ||
185 | void AliESDv0::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { | |
186 | //-------------------------------------------------------------------- | |
187 | // This function returns V0's position (global) | |
188 | //-------------------------------------------------------------------- | |
189 | x=fPos[0]; | |
190 | y=fPos[1]; | |
191 | z=fPos[2]; | |
192 | } | |
193 | ||
194 | Double_t AliESDv0::GetD(Double_t x0, Double_t y0, Double_t z0) const { | |
195 | //-------------------------------------------------------------------- | |
196 | // This function returns V0's impact parameter | |
197 | //-------------------------------------------------------------------- | |
198 | Double_t x=fPos[0],y=fPos[1],z=fPos[2]; | |
199 | Double_t px=fNmom[0]+fPmom[0]; | |
200 | Double_t py=fNmom[1]+fPmom[1]; | |
201 | Double_t pz=fNmom[2]+fPmom[2]; | |
202 | ||
203 | Double_t dx=(y0-y)*pz - (z0-z)*py; | |
204 | Double_t dy=(x0-x)*pz - (z0-z)*px; | |
205 | Double_t dz=(x0-x)*py - (y0-y)*px; | |
206 | Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); | |
207 | return d; | |
208 | } |