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[u/mrichter/AliRoot.git] / STEER / AliESDcascade.cxx
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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
32ClassImp(AliESDcascade)
33
90e48c0c 34AliESDcascade::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 48Double_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
120void
121AliESDcascade::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
130void 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
139Double_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