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[u/mrichter/AliRoot.git] / STEER / STEERBase / AliVParticle.cxx
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6bc03c45 1/**************************************************************************
2 * Copyright(c) 1998-2007, 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
16/* $Id$ */
17
18//-------------------------------------------------------------------------
19// base class for ESD and AOD particles
20// Author: Markus Oldenburg, CERN
21//-------------------------------------------------------------------------
22
23#include "AliVParticle.h"
c683ddc2 24#include "TMath.h"
6bc03c45 25
26ClassImp(AliVParticle)
27
28AliVParticle::AliVParticle(const AliVParticle& vPart) :
ddfbc51a 29 TObject(vPart) { } // Copy constructor
6bc03c45 30
31AliVParticle& AliVParticle::operator=(const AliVParticle& vPart)
32{ if (this!=&vPart) {
33 TObject::operator=(vPart);
34 }
ddfbc51a 35
6bc03c45 36 return *this;
37}
c683ddc2 38
39Bool_t AliVParticle::Local2GlobalMomentum(Double_t p[3], Double_t alpha) const {
40 //----------------------------------------------------------------
41 // This function performs local->global transformation of the
42 // track momentum.
43 // When called, the arguments are:
44 // p[0] = 1/pt * charge of the track;
45 // p[1] = sine of local azim. angle of the track momentum;
46 // p[2] = tangent of the track momentum dip angle;
47 // alpha - rotation angle.
48 // The result is returned as:
49 // p[0] = px
50 // p[1] = py
51 // p[2] = pz
52 // Results for (nearly) straight tracks are meaningless !
53 //----------------------------------------------------------------
54 if (TMath::Abs(p[0])<=kAlmost0) return kFALSE;
55 if (TMath::Abs(p[1])> kAlmost1) return kFALSE;
56
57 Double_t pt=1./TMath::Abs(p[0]);
58 Double_t cs=TMath::Cos(alpha), sn=TMath::Sin(alpha);
60e55aee 59 Double_t r=TMath::Sqrt((1. - p[1])*(1. + p[1]));
c683ddc2 60 p[0]=pt*(r*cs - p[1]*sn); p[1]=pt*(p[1]*cs + r*sn); p[2]=pt*p[2];
61
62 return kTRUE;
63}
64
65Bool_t AliVParticle::Local2GlobalPosition(Double_t r[3], Double_t alpha) const {
66 //----------------------------------------------------------------
67 // This function performs local->global transformation of the
68 // track position.
69 // When called, the arguments are:
70 // r[0] = local x
71 // r[1] = local y
72 // r[2] = local z
73 // alpha - rotation angle.
74 // The result is returned as:
75 // r[0] = global x
76 // r[1] = global y
77 // r[2] = global z
78 //----------------------------------------------------------------
79 Double_t cs=TMath::Cos(alpha), sn=TMath::Sin(alpha), x=r[0];
80 r[0]=x*cs - r[1]*sn; r[1]=x*sn + r[1]*cs;
81
82 return kTRUE;
83}
84
85Bool_t AliVParticle::Global2LocalMomentum(Double_t p[3], Short_t charge, Double_t &alpha) const {
86 //----------------------------------------------------------------
87 // This function performs global->local transformation of the
88 // track momentum.
89 // When called, the arguments are:
90 // p[0] = px
91 // p[1] = py
92 // p[2] = pz
93 // charge - of the track
94 // alpha - rotation angle.
95 // The result is returned as:
96 // p[0] = 1/pt * charge of the track;
97 // p[1] = sine of local azim. angle of the track momentum;
98 // p[2] = tangent of the track momentum dip angle;
99 // Results for (nearly) straight tracks are meaningless !
100 //----------------------------------------------------------------
101 double pt = TMath::Sqrt(p[0]*p[0]+p[1]*p[1]);
102 if (pt == 0.) return kFALSE;
103 alpha = TMath::Pi() + TMath::ATan2(-p[1], -p[0]);
104
105 p[0] = 1./pt * (float)charge;
106 p[1] = 0.;
107 p[2] = p[2]/pt;
108
109 return kTRUE;
110}
111
112Bool_t AliVParticle::Global2LocalPosition(Double_t r[3], Double_t alpha) const {
113 return Local2GlobalPosition(r, -alpha);
114}
115
5ffcfef5 116
117Int_t AliVParticle::Compare( const TObject* obj) const {
118
119 //
120 // see header file for class documentation
121 //
122
123 if (this == obj)
124 return 0;
125 // check type
126 if ( Pt() < ((AliVParticle*)(obj))->Pt())
127 return 1;
128 else
129 return -1;
130}
131