EvtVSSMix.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 1998      Caltech, UCSB
//
// Module: EvtVSSMix.cc
//
// Description: Routine to decay vector-> scalar scalar
//
// Modification history:
//
//    RYD       November 24, 1996       Module created
//
//------------------------------------------------------------------------
//
#include "EvtVSSMix.hh"
#include "../EvtGenBase/EvtConst.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtId.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <stdlib.h>
#include <string>
 
EvtVSSMix::~EvtVSSMix() {}
 
void EvtVSSMix::getName( std::string& model_name ) { model_name = "VSS_MIX"; }
 
EvtDecayBase* EvtVSSMix::clone() { return new EvtVSSMix; }
 
void EvtVSSMix::init() {
 
  // check that there are 1 arguments
  checkNArg( 1 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::VECTOR );
 
  checkSpinDaughter( 0, EvtSpinType::SCALAR );
  checkSpinDaughter( 1, EvtSpinType::SCALAR );
}
 
void EvtVSSMix::initProbMax() { setProbMax( 0.5 ); }
 
void EvtVSSMix::decay( EvtParticle* p ) {
 
  // added by Lange Jan4,2000
  static EvtId B0  = EvtPDL::getId( "B0" );
  static EvtId B0B = EvtPDL::getId( "anti-B0" );
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
  EvtParticle *s1, *s2;
  s1                = p->getDaug( 0 );
  s2                = p->getDaug( 1 );
  EvtVector4R s1mom = s1->getP4();
 
  double t1, t2, dm;
 
  s1->setLifetime();
  s2->setLifetime();
 
  t1 = s1->getLifetime();
  t2 = s2->getLifetime();
 
  // dm should probably be a parameter to this model.
 
  dm = getArg( 0 ) / EvtConst::c;
 
  EvtId d1, d2;
 
  d1 = s1->getId();
  d2 = s2->getId();
 
  double mix_amp = 0.;
  if ( d1 == B0 && d2 == B0B ) mix_amp = cos( 0.5 * dm * ( t1 - t2 ) );
  if ( d1 == B0B && d2 == B0 ) mix_amp = cos( 0.5 * dm * ( t1 - t2 ) );
  if ( d1 == B0 && d2 == B0 ) mix_amp = sin( 0.5 * dm * ( t1 - t2 ) );
  if ( d1 == B0B && d2 == B0B ) mix_amp = sin( 0.5 * dm * ( t1 - t2 ) );
 
  double norm = 1.0 / s1mom.d3mag();
 
  vertex( 0, norm * mix_amp * s1mom * ( p->eps( 0 ) ) );
  vertex( 1, norm * mix_amp * s1mom * ( p->eps( 1 ) ) );
  vertex( 2, norm * mix_amp * s1mom * ( p->eps( 2 ) ) );
 
  return;
}