Revision 4bee12876976bec72820e6464bf8665e58e624d0 authored by Gerardo Ganis on 24 July 2009, 07:33:50 UTC, committed by Gerardo Ganis on 24 July 2009, 07:33:50 UTC
git-svn-id: http://root.cern.ch/svn/root/branches/v5-24-00-patches@29570 27541ba8-7e3a-0410-8455-c3a389f83636
1 parent 3517aba
BoostY.cxx
// @(#)root/mathcore:$Id$
// Authors: M. Fischler 2005
/**********************************************************************
* *
* Copyright (c) 2005 , LCG ROOT FNAL MathLib Team *
* *
* *
**********************************************************************/
// Header file for class BoostY, a 4x4 symmetric matrix representation of
// an axial Lorentz transformation
//
// Created by: Mark Fischler Mon Nov 1 2005
//
#include "Math/GenVector/BoostY.h"
#include "Math/GenVector/LorentzVector.h"
#include "Math/GenVector/PxPyPzE4D.h"
#include "Math/GenVector/DisplacementVector3D.h"
#include "Math/GenVector/Cartesian3D.h"
#include "Math/GenVector/GenVector_exception.h"
#include <cmath>
#include <algorithm>
namespace ROOT {
namespace Math {
BoostY::BoostY() : fBeta(0.0), fGamma(1.0) {}
void BoostY::SetComponents (Scalar by) {
// set component
Scalar bp2 = by*by;
if (bp2 >= 1) {
GenVector::Throw(
"Beta Vector supplied to set BoostY represents speed >= c");
return;
}
fBeta = by;
fGamma = 1.0 / std::sqrt(1.0-bp2);
}
void BoostY::GetComponents (Scalar& by) const {
// get component
by = fBeta;
}
DisplacementVector3D< Cartesian3D<BoostY::Scalar> >
BoostY::BetaVector() const {
// return beta vector
return DisplacementVector3D< Cartesian3D<Scalar> > ( 0.0, fBeta, 0.0 );
}
void BoostY::GetLorentzRotation (Scalar r[]) const {
// get corresponding LorentzRotation
r[kLXX] = 1.0; r[kLXY] = 0.0; r[kLXZ] = 0.0; r[kLXT] = 0.0;
r[kLYX] = 0.0; r[kLYY] = fGamma; r[kLYZ] = 0.0; r[kLYT] = fGamma*fBeta;
r[kLZX] = 0.0; r[kLZY] = 0.0; r[kLZZ] = 1.0; r[kLZT] = 0.0;
r[kLTX] = 0.0; r[kLTY] = fGamma*fBeta; r[kLTZ] = 0.0; r[kLTT] = fGamma;
}
void BoostY::Rectify() {
// Assuming the representation of this is close to a true Lorentz Rotation,
// but may have drifted due to round-off error from many operations,
// this forms an "exact" orthosymplectic matrix for the Lorentz Rotation
// again.
if (fGamma <= 0) {
GenVector::Throw (
"Attempt to rectify a boost with non-positive gamma");
return;
}
Scalar beta = fBeta;
if ( beta >= 1 ) {
beta /= ( beta * ( 1.0 + 1.0e-16 ) );
}
SetComponents ( beta );
}
LorentzVector< PxPyPzE4D<double> >
BoostY::operator() (const LorentzVector< PxPyPzE4D<double> > & v) const {
// apply boost to a LV
Scalar y = v.Py();
Scalar t = v.E();
return LorentzVector< PxPyPzE4D<double> >
( v.Px()
, fGamma*y + fGamma*fBeta*t
, v.Pz()
, fGamma*fBeta*y + fGamma*t );
}
void BoostY::Invert() {
// invert Boost
fBeta = -fBeta;
}
BoostY BoostY::Inverse() const {
// return inverse
BoostY tmp(*this);
tmp.Invert();
return tmp;
}
// ========== I/O =====================
std::ostream & operator<< (std::ostream & os, const BoostY & b) {
os << " BoostY( beta: " << b.Beta() << ", gamma: " << b.Gamma() << " ) ";
return os;
}
} //namespace Math
} //namespace ROOT
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