EvtDeBD.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of models developed at BES collaboration
//      based on the EvtGen framework.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/BesCopyright
//      Copyright (A) 2006      Ping Rong-Gang, Pang Cai-Ying@IHEP
//
// Module: EvtDeBD.cc
//
// Description: To generate events for decuplet baryon deacys.
//
// Modification history:
//
//    Ping R.-G.    Apr., 2007       Module created
//
//------------------------------------------------------------------------
//
#include "EvtDeBD.hh"
#include "../EvtGenBase/EvtDiracSpinor.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtHelSys.hh"
#include "../EvtGenBase/EvtId.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtRaritaSchwinger.hh"
#include "../EvtGenBase/EvtRaritaSchwingerParticle.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <iostream>
#include <stdlib.h>
#include <string>
 
using std::cout;
using std::endl;
 
EvtDeBD::~EvtDeBD() {}
 
void EvtDeBD::getName( std::string& model_name ) { model_name = "DeBD"; }
 
EvtDecayBase* EvtDeBD::clone() { return new EvtDeBD; }
 
void EvtDeBD::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::RARITASCHWINGER );
 
  checkSpinDaughter( 0, EvtSpinType::DIRAC );
  checkSpinDaughter( 1, EvtSpinType::SCALAR );
}
 
/*
void EvtDeBD::initProbMax(){
  setProbMax(10.0);
}
*/
 
void EvtDeBD::decay( EvtParticle* p ) {
 
  static EvtId PIM = EvtPDL::getId( "pi-" );
  static EvtId PI0 = EvtPDL::getId( "pi0" );
  static EvtId KM  = EvtPDL::getId( "K-" );
 
  static EvtId L0  = EvtPDL::getId( "Lambda0" );
  static EvtId LB  = EvtPDL::getId( "anti-Lambda0" );
  static EvtId XM  = EvtPDL::getId( "Xi-" );
  static EvtId XMB = EvtPDL::getId( "anti-Xi+" );
  static EvtId X0  = EvtPDL::getId( "Xi0" );
  static EvtId X0B = EvtPDL::getId( "anti-Xi0" );
 
  static EvtId OM  = EvtPDL::getId( "Omega-" );
  static EvtId OMB = EvtPDL::getId( "anti-Omega+" );
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  EvtParticle *l1, *l2;
  l1 = p->getDaug( 0 );
  l2 = p->getDaug( 1 );
 
  EvtId p1, d1, d2;
  p1 = p->getId();
  d1 = l1->getId();
  d2 = l2->getId();
 
  EvtVector4R pDaug = l1->getP4();
  double      p3    = pDaug.d3mag();
 
  EvtVector4R pv, ps, ppr;
  pv  = l1->getP4Lab(); // baryon
  ps  = l2->getP4Lab(); // meson
  ppr = p->getP4();
 
  double    theta, alpha;
  EvtHelSys angles( ppr, pv ); // using helicity sys.angles
  theta        = angles.getHelAng( 1 );
  double phi   = angles.getHelAng( 2 );
  double gamma = 0;
 
  if ( ( p1 == OM ) && ( d1 == L0 ) ) { alpha = 0.0175; }
  else if ( ( p1 == OMB ) && ( d1 == LB ) ) { alpha = -0.0175; }
  else if ( ( p1 == OM ) && ( d1 == X0 ) ) { alpha = 0.09; }
  else if ( ( p1 == OMB ) || ( d1 == X0B ) ) { alpha = -0.09; }
  else if ( ( p1 == OM ) || ( d1 == XM ) ) { alpha = 0.05; }
  else if ( ( p1 == OMB ) || ( d1 == XMB ) ) { alpha = -0.05; }
 
  double FP, FM;
  if ( p1 == OM || p1 == OMB )
  {
    FM = sqrt( ( 1 + alpha ) / 2. );
    FP = sqrt( ( 1 - alpha ) / 2. );
  }
  else
  {
    FP = 1;
    FM = 1;
  }
 
  vertex( 0, 0, Djmn( 1.5, 0.5, 0.5, phi, theta, gamma ) * FP );
  vertex( 0, 1, Djmn( 1.5, 0.5, -0.5, phi, theta, gamma ) * FM );
  vertex( 1, 0, Djmn( 1.5, 1.5, 0.5, phi, theta, gamma ) * FP );
  vertex( 1, 1, Djmn( 1.5, 1.5, -0.5, phi, theta, gamma ) * FM );
  vertex( 2, 0, Djmn( 1.5, -1.5, 0.5, phi, theta, gamma ) * FP );
  vertex( 2, 1, Djmn( 1.5, -1.5, -0.5, phi, theta, gamma ) * FM );
  vertex( 3, 0, Djmn( 1.5, -0.5, 0.5, phi, theta, gamma ) * FP );
  vertex( 3, 1, Djmn( 1.5, -0.5, -0.5, phi, theta, gamma ) * FM );
 
  return;
}