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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 cascade vertex class | |
4f679a16 | 20 | // This is part of the Event Summary Data |
21 | // which contains the result of the reconstruction | |
22 | // and is the main set of classes for analaysis | |
e23730c7 | 23 | // Origin: Christian Kuhn, IReS, Strasbourg, christian.kuhn@ires.in2p3.fr |
24 | //------------------------------------------------------------------------- | |
4f679a16 | 25 | |
90e48c0c | 26 | #include <TDatabasePDG.h> |
e23730c7 | 27 | #include <TMath.h> |
28 | ||
5f7789fc | 29 | #include "AliLog.h" |
e23730c7 | 30 | #include "AliESDcascade.h" |
e23730c7 | 31 | |
32 | ClassImp(AliESDcascade) | |
33 | ||
90e48c0c | 34 | AliESDcascade::AliESDcascade() : |
35 | TObject(), | |
36 | fPdgCode(kXiMinus), | |
37 | fEffMass(TDatabasePDG::Instance()->GetParticle(kXiMinus)->Mass()), | |
38 | fChi2(1.e+33), | |
39 | fBachIdx(0) | |
40 | { | |
e23730c7 | 41 | //-------------------------------------------------------------------- |
42 | // Default constructor (Xi-) | |
43 | //-------------------------------------------------------------------- | |
e23730c7 | 44 | fPos[0]=fPos[1]=fPos[2]=0.; |
45 | fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.; | |
46 | } | |
47 | ||
e23730c7 | 48 | Double_t AliESDcascade::ChangeMassHypothesis(Double_t &v0q, Int_t code) { |
49 | //-------------------------------------------------------------------- | |
50 | // This function changes the mass hypothesis for this cascade | |
51 | // and returns the "kinematical quality" of this hypothesis | |
52 | // together with the "quality" of associated V0 (argument v0q) | |
53 | //-------------------------------------------------------------------- | |
54 | Double_t nmass=0.13957, pmass=0.93827, ps0=0.101; | |
55 | Double_t bmass=0.13957, mass =1.3213, ps =0.139; | |
56 | ||
57 | fPdgCode=code; | |
58 | ||
59 | switch (code) { | |
60 | case 213: | |
61 | bmass=0.93827; | |
62 | break; | |
63 | case kXiMinus: | |
64 | break; | |
65 | case kXiPlusBar: | |
66 | nmass=0.93827; pmass=0.13957; | |
67 | break; | |
68 | case kOmegaMinus: | |
69 | bmass=0.49368; mass=1.67245; ps=0.211; | |
70 | break; | |
71 | case kOmegaPlusBar: | |
72 | nmass=0.93827; pmass=0.13957; | |
73 | bmass=0.49368; mass=1.67245; ps=0.211; | |
74 | break; | |
75 | default: | |
5f7789fc | 76 | AliError("Invalide PDG code ! Assuming XiMinus's..."); |
e23730c7 | 77 | fPdgCode=kXiMinus; |
78 | break; | |
79 | } | |
80 | ||
81 | Double_t pxn=fV0mom[0][0], pyn=fV0mom[0][1], pzn=fV0mom[0][2]; | |
82 | Double_t pxp=fV0mom[1][0], pyp=fV0mom[1][1], pzp=fV0mom[1][2]; | |
83 | Double_t px0=pxn+pxp, py0=pyn+pyp, pz0=pzn+pzp; | |
84 | Double_t p0=TMath::Sqrt(px0*px0 + py0*py0 + pz0*pz0); | |
85 | ||
86 | Double_t e0=TMath::Sqrt(1.11568*1.11568 + p0*p0); | |
87 | Double_t beta0=p0/e0; | |
88 | Double_t pln=(pxn*px0 + pyn*py0 + pzn*pz0)/p0; | |
89 | Double_t plp=(pxp*px0 + pyp*py0 + pzp*pz0)/p0; | |
90 | Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; | |
91 | ||
92 | Double_t a=(plp-pln)/(plp+pln); | |
93 | a -= (pmass*pmass-nmass*nmass)/(1.11568*1.11568); | |
94 | a = 0.25*beta0*beta0*1.11568*1.11568*a*a + pt2; | |
95 | ||
96 | ||
97 | v0q=a - ps0*ps0; | |
98 | ||
99 | ||
100 | Double_t pxb=fBachMom[0], pyb=fBachMom[1], pzb=fBachMom[2]; | |
101 | ||
102 | Double_t eb=TMath::Sqrt(bmass*bmass + pxb*pxb + pyb*pyb + pzb*pzb); | |
103 | Double_t pxl=px0+pxb, pyl=py0+pyb, pzl=pz0+pzb; | |
104 | Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); | |
105 | ||
106 | fEffMass=TMath::Sqrt((e0+eb)*(e0+eb) - pl*pl); | |
107 | ||
108 | Double_t beta=pl/(e0+eb); | |
109 | Double_t pl0=(px0*pxl + py0*pyl + pz0*pzl)/pl; | |
110 | Double_t plb=(pxb*pxl + pyb*pyl + pzb*pzl)/pl; | |
111 | pt2=p0*p0 - pl0*pl0; | |
112 | ||
113 | a=(pl0-plb)/(pl0+plb); | |
114 | a -= (1.11568*1.11568-bmass*bmass)/(mass*mass); | |
115 | a = 0.25*beta*beta*mass*mass*a*a + pt2; | |
116 | ||
117 | return (a - ps*ps); | |
118 | } | |
119 | ||
120 | void | |
121 | AliESDcascade::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { | |
122 | //-------------------------------------------------------------------- | |
123 | // This function returns the cascade momentum (global) | |
124 | //-------------------------------------------------------------------- | |
125 | px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0]; | |
126 | py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1]; | |
127 | pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2]; | |
128 | } | |
129 | ||
130 | void AliESDcascade::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { | |
131 | //-------------------------------------------------------------------- | |
132 | // This function returns cascade position (global) | |
133 | //-------------------------------------------------------------------- | |
134 | x=fPos[0]; | |
135 | y=fPos[1]; | |
136 | z=fPos[2]; | |
137 | } | |
138 | ||
139 | Double_t AliESDcascade::GetD(Double_t x0, Double_t y0, Double_t z0) const { | |
140 | //-------------------------------------------------------------------- | |
141 | // This function returns the cascade impact parameter | |
142 | //-------------------------------------------------------------------- | |
143 | ||
144 | Double_t x=fPos[0],y=fPos[1],z=fPos[2]; | |
145 | Double_t px=fV0mom[0][0]+fV0mom[1][0]+fBachMom[0]; | |
146 | Double_t py=fV0mom[0][1]+fV0mom[1][1]+fBachMom[1]; | |
147 | Double_t pz=fV0mom[0][2]+fV0mom[1][2]+fBachMom[2]; | |
148 | ||
149 | Double_t dx=(y0-y)*pz - (z0-z)*py; | |
150 | Double_t dy=(x0-x)*pz - (z0-z)*px; | |
151 | Double_t dz=(x0-x)*py - (y0-y)*px; | |
152 | Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); | |
153 | ||
154 | return d; | |
155 | } | |
156 |