| Geant4 Cross Reference |
1 // -*- C++ -*- 1 // -*- C++ -*-
2 // ------------------------------------------- 2 // ---------------------------------------------------------------------------
3 // 3 //
4 // This file is a part of the CLHEP - a Class 4 // This file is a part of the CLHEP - a Class Library for High Energy Physics.
5 // 5 //
6 // This is the implementation of the HepLorent 6 // This is the implementation of the HepLorentzVector class:
7 // Those methods originating in ZOOM dealing w 7 // Those methods originating in ZOOM dealing with simple boosts and rotations.
8 // Use of one of these methods will not force 8 // Use of one of these methods will not force loading of the HepRotation or
9 // HepLorentzRotation class. 9 // HepLorentzRotation class.
10 // 10 //
11 11
12 #include "CLHEP/Vector/LorentzVector.h" 12 #include "CLHEP/Vector/LorentzVector.h"
13 13
14 #include <cmath> 14 #include <cmath>
15 #include <iostream> 15 #include <iostream>
16 16
17 namespace CLHEP { 17 namespace CLHEP {
18 18
19 //-********* 19 //-*********
20 // rotationOf() 20 // rotationOf()
21 //-********* 21 //-*********
22 22
23 // Each of these is a shell over a rotate meth 23 // Each of these is a shell over a rotate method.
24 24
25 HepLorentzVector rotationXOf 25 HepLorentzVector rotationXOf
26 (const HepLorentzVector & vec, double phi){ 26 (const HepLorentzVector & vec, double phi){
27 HepLorentzVector vv (vec); 27 HepLorentzVector vv (vec);
28 return vv.rotateX (phi); 28 return vv.rotateX (phi);
29 } 29 }
30 30
31 HepLorentzVector rotationYOf 31 HepLorentzVector rotationYOf
32 (const HepLorentzVector & vec, double phi){ 32 (const HepLorentzVector & vec, double phi){
33 HepLorentzVector vv (vec); 33 HepLorentzVector vv (vec);
34 return vv.rotateY (phi); 34 return vv.rotateY (phi);
35 } 35 }
36 36
37 HepLorentzVector rotationZOf 37 HepLorentzVector rotationZOf
38 (const HepLorentzVector & vec, double phi){ 38 (const HepLorentzVector & vec, double phi){
39 HepLorentzVector vv (vec); 39 HepLorentzVector vv (vec);
40 return vv.rotateZ (phi); 40 return vv.rotateZ (phi);
41 } 41 }
42 42
43 //-******** 43 //-********
44 // boost 44 // boost
45 //-******** 45 //-********
46 46
47 HepLorentzVector & HepLorentzVector::boost 47 HepLorentzVector & HepLorentzVector::boost
48 ( const Hep3Vector & aaxis, double bbet 48 ( const Hep3Vector & aaxis, double bbeta ) {
49 if (bbeta==0) { 49 if (bbeta==0) {
50 return *this; // do nothing for a 0 boost 50 return *this; // do nothing for a 0 boost
51 } 51 }
52 double r2 = aaxis.mag2(); 52 double r2 = aaxis.mag2();
53 if ( r2 == 0 ) { 53 if ( r2 == 0 ) {
54 std::cerr << "HepLorentzVector::boost() - 54 std::cerr << "HepLorentzVector::boost() - "
55 << "A zero vector used as axis defining 55 << "A zero vector used as axis defining a boost -- no boost done"
56 << std::endl; 56 << std::endl;
57 return *this; 57 return *this;
58 } 58 }
59 double b2 = bbeta*bbeta; 59 double b2 = bbeta*bbeta;
60 if (b2 >= 1) { 60 if (b2 >= 1) {
61 std::cerr << "HepLorentzVector::boost() - 61 std::cerr << "HepLorentzVector::boost() - "
62 << "LorentzVector boosted with beta >= 1 62 << "LorentzVector boosted with beta >= 1 (speed of light) -- \n"
63 << "no boost done" << std::endl; 63 << "no boost done" << std::endl;
64 } else { 64 } else {
65 Hep3Vector u = aaxis.unit(); 65 Hep3Vector u = aaxis.unit();
66 double ggamma = std::sqrt(1./(1.-b2)); 66 double ggamma = std::sqrt(1./(1.-b2));
67 double betaDotV = u.dot(pp)*bbeta; 67 double betaDotV = u.dot(pp)*bbeta;
68 double tt = ee; 68 double tt = ee;
69 69
70 ee = ggamma * (tt + betaDotV); 70 ee = ggamma * (tt + betaDotV);
71 pp += ( ((ggamma-1)/b2)*betaDotV*bbeta + g 71 pp += ( ((ggamma-1)/b2)*betaDotV*bbeta + ggamma*bbeta*tt ) * u;
72 // Note: I have verified the behavior of 72 // Note: I have verified the behavior of this even when beta is very
73 // small -- (gamma-1)/b2 becomes in 73 // small -- (gamma-1)/b2 becomes inaccurate by O(1), but it is then
74 // multiplied by O(beta**2) and add 74 // multiplied by O(beta**2) and added to an O(beta) term, so the
75 // inaccuracy does not affect the f 75 // inaccuracy does not affect the final result.
76 } 76 }
77 return *this; 77 return *this;
78 } /* boost (axis, beta) */ 78 } /* boost (axis, beta) */
79 79
80 } // namespace CLHEP 80 } // namespace CLHEP
81 81