EvtSVSCPLH.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) 2001      Caltech, UCSB
//
// Module: EvtSVSCPLH.cc
//
// Description: The decay of a scalar to a scalar and a vector particle are
//              performed with CP violation and different widths for
//              the cp even and odd states. E.g. B->J/psi K_S.
//
// Modification history:
//
//    Ryd       March 29, 2001       Module created
//
//------------------------------------------------------------------------
//
#include "EvtSVSCPLH.hh"
#include "../EvtGenBase/EvtCPUtil.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>
using std::endl;
 
EvtSVSCPLH::~EvtSVSCPLH() {}
 
void EvtSVSCPLH::getName( std::string& model_name ) { model_name = "SVS_CPLH"; }
 
EvtDecayBase* EvtSVSCPLH::clone() { return new EvtSVSCPLH; }
 
void EvtSVSCPLH::init() {
 
  // check that there are 8 arguments
  checkNArg( 8 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::SCALAR );
 
  checkSpinDaughter( 0, EvtSpinType::VECTOR );
  checkSpinDaughter( 1, EvtSpinType::SCALAR );
 
  static double ctau = EvtPDL::getctau( EvtPDL::getId( "B0" ) );
 
  // hbar/s
  _dm     = getArg( 0 );
  _dgamma = EvtConst::c * getArg( 1 ) / ctau;
 
  _qop = getArg( 2 ) * exp( EvtComplex( 0.0, getArg( 3 ) ) );
 
  _poq = 1.0 / _qop;
 
  _Af    = getArg( 4 ) * exp( EvtComplex( 0.0, getArg( 5 ) ) );
  _Abarf = getArg( 6 ) * exp( EvtComplex( 0.0, getArg( 7 ) ) );
 
  if ( verbose() )
  {
    report( INFO, "EvtGen" ) << ":EvtSVSCPLH:dm=" << _dm << endl;
    report( INFO, "EvtGen" ) << ":EvtSVSCPLH:dGamma=" << _dgamma << endl;
    report( INFO, "EvtGen" ) << ":EvtSVSCPLH:q/p=" << _qop << endl;
    report( INFO, "EvtGen" ) << ":EvtSVSCPLH:Af=" << _Af << endl;
    report( INFO, "EvtGen" ) << ":EvtSVSCPLH:Abarf=" << _Abarf << endl;
  }
}
 
void EvtSVSCPLH::initProbMax() {
 
  // This is probably not quite right, but it should do as a start...
  // Anders
 
  setProbMax( 4.0 * ( getArg( 4 ) * getArg( 4 ) + getArg( 6 ) * getArg( 6 ) ) );
}
 
void EvtSVSCPLH::decay( EvtParticle* p ) {
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  static EvtId B0  = EvtPDL::getId( "B0" );
  static EvtId B0B = EvtPDL::getId( "anti-B0" );
 
  double t;
  EvtId  other_b;
 
  EvtCPUtil::OtherB( p, t, other_b, 0.5 );
 
  // convert time from mm to seconds
  t /= EvtConst::c;
 
  // sign convention is dm=Mheavy-Mlight
  //                    dGamma=Gammalight-Gammaheavy
  // such that in the standard model both of these are positive.
  EvtComplex gp = 0.5 * ( exp( EvtComplex( 0.25 * t * _dgamma, -0.5 * t * _dm ) ) +
                          exp( EvtComplex( -0.25 * t * _dgamma, 0.5 * t * _dm ) ) );
  EvtComplex gm = 0.5 * ( exp( EvtComplex( 0.25 * t * _dgamma, -0.5 * t * _dm ) ) -
                          exp( EvtComplex( -0.25 * t * _dgamma, 0.5 * t * _dm ) ) );
 
  EvtComplex amp;
 
  if ( other_b == B0B ) { amp = gp * _Af + _qop * gm * _Abarf; }
  else if ( other_b == B0 ) { amp = gp * _Abarf + _poq * gm * _Af; }
  else
  {
    report( ERROR, "EvtGen" ) << "other_b was not B0 or B0B!" << endl;
    ::abort();
  }
 
  EvtVector4R p4_parent = p->getP4Restframe();
  ;
 
  double norm =
      p->getDaug( 0 )->mass() / ( p->getDaug( 0 )->getP4().d3mag() * p4_parent.mass() );
 
  EvtParticle* v = p->getDaug( 0 );
 
  vertex( 0, amp * norm * ( p4_parent * ( v->epsParent( 0 ) ) ) );
  vertex( 1, amp * norm * ( p4_parent * ( v->epsParent( 1 ) ) ) );
  vertex( 2, amp * norm * ( p4_parent * ( v->epsParent( 2 ) ) ) );
 
  return;
}