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QtildaShowerKinematics1to2.cc
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QtildaShowerKinematics1to2.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the QtildaShowerKinematics1to2 class.
//
#include "QtildaShowerKinematics1to2.h"
#include "Herwig++/Utilities/HwDebug.h"
#include "ThePEG/Repository/EventGenerator.h"
#include "ThePEG/CLHEPWrap/Lorentz5Vector.h"
#include "ThePEG/Repository/CurrentGenerator.h"
using namespace Herwig;
QtildaShowerKinematics1to2::~QtildaShowerKinematics1to2() {}
vector<Lorentz5Momentum> QtildaShowerKinematics1to2::getBasis() {
//cerr << "*";
vector<Lorentz5Momentum> dum;
//cerr << "*";
dum.clear();
//cerr << "*";
dum.push_back( _pVector );
//cerr << "*";
dum.push_back( _nVector );
//cerr << "*";
//cerr << dum[0] << endl;
//cerr << dum[1] << endl;
return dum;
}
// --- protected tools ---
Lorentz5Momentum QtildaShowerKinematics1to2::
sudakov2Momentum(double alpha, double beta, Energy px, Energy py) {
// gives loads of output to check the transformations...
const Hep3Vector beta_bb = -(_pVector + _nVector).boostVector();
// see also these methods!
// Hep3Vector findBoostToCM() const;
// // Boost needed to get to center-of-mass frame:
// // w.findBoostToCM() == - w.boostVector()
// // w.boost(w.findBoostToCM()) == w.rest4Vector()
// Hep3Vector findBoostToCM( const HepLorentzVector & w ) const;
// // Boost needed to get to combined center-of-mass frame:
// // w1.findBoostToCM(w2) == w2.findBoostToCM(w1)
// // w.findBoostToCM(w) == w.findBoostToCM()
Lorentz5Momentum p_bb = _pVector;
Lorentz5Momentum n_bb = _nVector;
p_bb.boost( beta_bb );
n_bb.boost( beta_bb );
if ( HERWIG_DEBUG_LEVEL >= HwDebug::full_Shower ) {
if ( (p_bb[0] + n_bb[0] > 1.0*eV) || (p_bb[1] + n_bb[1] > 1.*eV) || (p_bb[2] + n_bb[2] > 1.*eV) ) {
CurrentGenerator::log() << "QtildaShowerKinematics1to2::sudakov2Momentum(): "
<< " Warning! check failed: haven't got to b2b-frame!"
<< endl;
}
}
if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
CurrentGenerator::log() << "QtildaShowerKinematics1to2::sudakov2Momentum(): extreme ________________________" << endl;
}
if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
CurrentGenerator::log() << " called with (a, b, px, py) = (" << alpha
<< ", " << beta
<< ", " << px
<< ", " << py
<< ") "
<< endl
<< " LAB: p = " << _pVector
<< endl
<< " n = " << _nVector << endl
<< " p+n = " << _pVector + _nVector << endl
<< " (p.n, p2, n2) = (" << _pVector*_nVector
<< ", " << _pVector.mass2()
<< ", " << _nVector.mass2()
<< ")"
<< endl
<< " to b2b frame: beta = " << beta_bb
<< endl
<< " b2b: p = " << p_bb
<< endl
<< " n = " << n_bb
<< endl
<< " p+n = " << p_bb + n_bb
<< endl
<< " (p.n, p2, n2) = (" << p_bb*n_bb
<< ", " << p_bb.mass2()
<< ", " << n_bb.mass2()
<< ")"
<< endl;
}
// set first in b2b frame along z-axis (assuming that p and n are
// b2b as checked above)
Lorentz5Momentum dq(0.0, 0.0, (alpha - beta)*p_bb.vect().mag(),
alpha*p_bb[3] + beta*n_bb[3] );
if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
CurrentGenerator::log() << " q = " << dq << " ...(= a p'' + b n'') along z-axis"
<< endl
<< " zxs: in (theta, phi) = (" << p_bb.theta()
<< ", " << p_bb.phi() << ")-direction. "
<< endl
<< " p_bb/|p_bb| = " << p_bb.vect()/p_bb.vect().mag()
<< endl
<< " q3/|q3| = " << dq.vect().rotateUz( p_bb.vect()/p_bb.vect().mag() )/dq.vect().rotateUz( p_bb.vect()/p_bb.vect().mag() ).mag()
<< endl;
}
// add transverse components
dq.setPx(px);
dq.setPy(py);
if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
CurrentGenerator::log() << " ...including p_T:"
<< endl
<< " q = " << dq
<< endl
<< " q2 = " << sqr(dq)
<< ", |q3| = " << dq.vect().mag()
<< endl;
}
// rotate to have z-axis parallel to p
dq.rotateUz( p_bb.vect()/p_bb.vect().mag() );
if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
Hep3Vector qpar = (((dq.vect())*(p_bb.vect()))/sqr((p_bb.vect()).mag()))*p_bb.vect();
Hep3Vector qperp = dq.vect() - qpar;
CurrentGenerator::log() << " ...after rotation:"
<< endl
<< " q = " << dq
<< ", q2 = " << sqr(dq)
<< endl
<< " q-drctn (theta, phi) = ("
<< qpar.theta()
<< ", "
<< qpar.phi()
<< ")"
<< endl
<< " |q3|/given = "
<< qpar.mag()
<< "/" << (alpha - beta)*p_bb.vect().mag()
<< ", perp/given = " << qperp.mag()
<< "/" << sqrt(sqr(px) + sqr(py))
<< endl;
}
// boost back
dq.boost( -beta_bb );
dq.rescaleMass();
// check consistency by getting back the Sudakov components from
// the constructed momentum in the given basis
if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
double da = (dq*_nVector)/(_pVector*_nVector);
double db = (dq*_pVector - da*_pVector.m2())/(_pVector*_nVector);
double dq2 = - sqr( dq - da*_pVector - db*_nVector );
CurrentGenerator::log() << " ...after boost:"
<< " q = " << dq
<< ", q2 = " << sqr(dq)
<< endl
<< " check \t given \t\t result \t ok?" << endl
<< " alpha \t "
<< alpha << " \t " << da
<< (da - alpha < 1e-10 ? " \t ok " : " \t not ok!")
<< endl
<< " beta \t " << beta << " \t " << db
<< (db - beta < 1e-10 ? " \t ok " : " \t not ok!")
<< endl
<< " perp2 \t "
<< dq2 << " \t " << sqr(px) + sqr(py)
<< (sqr(px) + sqr(py) > 0 ?
( (dq2 - sqr(px) - sqr(py))/sqr(px + sqr(py))
< 1e-10 ? " \t ok " : " not \t ok!") : " \t can't check.")
<< endl
<< " (m2, (am)^2, 2ab p.n, (a m)^2+2ab p.n, q2) = " << endl
<< " given ("
<< _pVector.m2() << ", "
<< sqr(alpha)*_pVector.m2() << ", "
<< 2*alpha*beta*(_pVector*_nVector) << ", "
<< sqr(alpha)*_pVector.m2() + 2*alpha*beta*(_pVector*_nVector)
<< ", "
<< sqr(alpha)*_pVector.m2() + 2*alpha*beta*(_pVector*_nVector) - sqr(px) - sqr(py)
<< ")" << endl
<< " result ("
<< _pVector.m2() << ", "
<< sqr(da)*_pVector.m2() << ", "
<< 2*da*db*(_pVector*_nVector) << ", "
<< sqr(da)*_pVector.m2() + 2*da*db*(_pVector*_nVector)
<< ", "
<< sqr(da)*_pVector.m2() + 2*da*db*(_pVector*_nVector) - dq2
<< ")"
<< endl;
}
// if ( HERWIG_DEBUG_LEVEL >= HwDebug::extreme_Shower ) {
// CurrentGenerator::log() << "QtildaShowerKinematics1to2::sudakov2Momentum(): "
// << "==> end <==="
// << endl;
// }
return dq;
}

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