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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" |
34 | ||
35 | ClassImp(AliESDv0) | |
36 | ||
90e48c0c | 37 | AliESDv0::AliESDv0() : |
38 | TObject(), | |
39 | fPdgCode(kK0Short), | |
40 | fEffMass(TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass()), | |
17f7744d | 41 | fDcaDaughters(0), |
90e48c0c | 42 | fChi2(1.e+33), |
43 | fNidx(0), | |
44 | fPidx(0) | |
45 | { | |
e23730c7 | 46 | //-------------------------------------------------------------------- |
47 | // Default constructor (K0s) | |
48 | //-------------------------------------------------------------------- | |
6605de26 | 49 | |
50 | for (Int_t i=0; i<3; i++) { | |
51 | fPos[i] = 0.; | |
52 | fNmom[i] = 0.; | |
53 | fPmom[i] = 0.; | |
54 | } | |
55 | ||
56 | for (Int_t i=0; i<6; i++) { | |
57 | fPosCov[i]= 0.; | |
58 | fNmomCov[i] = 0.; | |
59 | fPmomCov[i] = 0.; | |
60 | } | |
e23730c7 | 61 | } |
62 | ||
63 | Double_t AliESDv0::ChangeMassHypothesis(Int_t code) { | |
64 | //-------------------------------------------------------------------- | |
65 | // This function changes the mass hypothesis for this V0 | |
66 | // and returns the "kinematical quality" of this hypothesis | |
67 | //-------------------------------------------------------------------- | |
68 | Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, ps=0.206; | |
69 | ||
70 | fPdgCode=code; | |
71 | ||
72 | switch (code) { | |
73 | case kLambda0: | |
74 | nmass=0.13957; pmass=0.93827; mass=1.1157; ps=0.101; break; | |
75 | case kLambda0Bar: | |
76 | pmass=0.13957; nmass=0.93827; mass=1.1157; ps=0.101; break; | |
77 | case kK0Short: | |
78 | break; | |
79 | default: | |
5f7789fc | 80 | AliError("invalide PDG code ! Assuming K0s..."); |
e23730c7 | 81 | fPdgCode=kK0Short; |
82 | break; | |
83 | } | |
84 | ||
85 | Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2]; | |
86 | Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2]; | |
87 | ||
88 | Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn); | |
89 | Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp); | |
90 | Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp; | |
91 | Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); | |
92 | ||
93 | fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl); | |
94 | ||
95 | Double_t beta=pl/(en+ep); | |
96 | Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl; | |
97 | Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl; | |
98 | ||
99 | Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; | |
100 | ||
101 | Double_t a=(plp-pln)/(plp+pln); | |
102 | a -= (pmass*pmass-nmass*nmass)/(mass*mass); | |
103 | a = 0.25*beta*beta*mass*mass*a*a + pt2; | |
104 | ||
105 | return (a - ps*ps); | |
106 | ||
107 | } | |
108 | ||
109 | void AliESDv0::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { | |
110 | //-------------------------------------------------------------------- | |
111 | // This function returns V0's momentum (global) | |
112 | //-------------------------------------------------------------------- | |
113 | px=fNmom[0]+fPmom[0]; | |
114 | py=fNmom[1]+fPmom[1]; | |
115 | pz=fNmom[2]+fPmom[2]; | |
116 | } | |
117 | ||
118 | void AliESDv0::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { | |
119 | //-------------------------------------------------------------------- | |
120 | // This function returns V0's position (global) | |
121 | //-------------------------------------------------------------------- | |
122 | x=fPos[0]; | |
123 | y=fPos[1]; | |
124 | z=fPos[2]; | |
125 | } | |
126 | ||
127 | Double_t AliESDv0::GetD(Double_t x0, Double_t y0, Double_t z0) const { | |
128 | //-------------------------------------------------------------------- | |
129 | // This function returns V0's impact parameter | |
130 | //-------------------------------------------------------------------- | |
131 | Double_t x=fPos[0],y=fPos[1],z=fPos[2]; | |
132 | Double_t px=fNmom[0]+fPmom[0]; | |
133 | Double_t py=fNmom[1]+fPmom[1]; | |
134 | Double_t pz=fNmom[2]+fPmom[2]; | |
135 | ||
136 | Double_t dx=(y0-y)*pz - (z0-z)*py; | |
137 | Double_t dy=(x0-x)*pz - (z0-z)*px; | |
138 | Double_t dz=(x0-x)*py - (y0-y)*px; | |
139 | Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); | |
140 | return d; | |
141 | } |