Gabriele Cosmo
81 lines
2.2 KiB
C++
81 lines
2.2 KiB
C++
// -*- C++ -*-
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// ---------------------------------------------------------------------------
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//
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// This file is a part of the CLHEP - a Class Library for High Energy Physics.
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//
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// This is the implementation of the HepLorentzVector class:
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// Those methods originating in ZOOM dealing with simple boosts and rotations.
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// Use of one of these methods will not force loading of the HepRotation or
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// HepLorentzRotation class.
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//
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#include "CLHEP/Vector/LorentzVector.h"
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#include <cmath>
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#include <iostream>
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namespace CLHEP {
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//-*********
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// rotationOf()
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//-*********
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// Each of these is a shell over a rotate method.
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HepLorentzVector rotationXOf
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(const HepLorentzVector & vec, double phi){
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HepLorentzVector vv (vec);
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return vv.rotateX (phi);
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}
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HepLorentzVector rotationYOf
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(const HepLorentzVector & vec, double phi){
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HepLorentzVector vv (vec);
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return vv.rotateY (phi);
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}
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HepLorentzVector rotationZOf
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(const HepLorentzVector & vec, double phi){
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HepLorentzVector vv (vec);
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return vv.rotateZ (phi);
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}
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//-********
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// boost
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//-********
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HepLorentzVector & HepLorentzVector::boost
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( const Hep3Vector & aaxis, double bbeta ) {
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if (bbeta==0) {
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return *this; // do nothing for a 0 boost
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}
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double r2 = aaxis.mag2();
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if ( r2 == 0 ) {
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std::cerr << "HepLorentzVector::boost() - "
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<< "A zero vector used as axis defining a boost -- no boost done"
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<< std::endl;
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return *this;
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}
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double b2 = bbeta*bbeta;
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if (b2 >= 1) {
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std::cerr << "HepLorentzVector::boost() - "
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<< "LorentzVector boosted with beta >= 1 (speed of light) -- \n"
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<< "no boost done" << std::endl;
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} else {
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Hep3Vector u = aaxis.unit();
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double ggamma = std::sqrt(1./(1.-b2));
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double betaDotV = u.dot(pp)*bbeta;
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double tt = ee;
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ee = ggamma * (tt + betaDotV);
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pp += ( ((ggamma-1)/b2)*betaDotV*bbeta + ggamma*bbeta*tt ) * u;
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// Note: I have verified the behavior of this even when beta is very
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// small -- (gamma-1)/b2 becomes inaccurate by O(1), but it is then
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// multiplied by O(beta**2) and added to an O(beta) term, so the
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// inaccuracy does not affect the final result.
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}
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return *this;
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} /* boost (axis, beta) */
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} // namespace CLHEP
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