EvtCPUtil.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: EvtCPUtil.cc
//
// Description: Utilities needed for generation of CP violating
//              decays.
//
// Modification history:
//
//    RYD     March 24, 1998         Module created
//
//------------------------------------------------------------------------
// 
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtScalarParticle.hh"
#include "EvtGenBase/EvtRandom.hh"
#include "EvtGenBase/EvtCPUtil.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtSymTable.hh"
#include "EvtGenBase/EvtConst.hh"
 
#include <assert.h>
#include <stdlib.h>
using std::endl;
 
 
//added two functions for finding the fraction of B0 tags for decays into 
//both CP eigenstates and non-CP eigenstates -- NK, Jan. 27th, 1998
 
void EvtCPUtil::fractB0CP(EvtComplex Af, EvtComplex Abarf, 
              double deltam, double beta, double &fract) {
//this function returns the number of B0 tags for decays into CP-eigenstates
//(the "probB0" in the new EvtOtherB)
 
  //double gamma_B = EvtPDL::getWidth(B0);   
  //double xd = deltam/gamma_B;
  //double xd = 0.65;
  double ratio = 1/(1 + 0.65*0.65);
  
  EvtComplex rf, rbarf;
 
  rf = EvtComplex(cos(2.0*beta),sin(2.0*beta))*Abarf/Af;
  rbarf = EvtComplex(1.0)/rf;
 
  double A2 = real(Af)*real(Af) + imag(Af)*imag(Af);
  double Abar2 = real(Abarf)*real(Abarf) + imag(Abarf)*imag(Abarf);
  
  double rf2 = real(rf)*real(rf) + imag(rf)*imag(rf);    
  double rbarf2 = real(rbarf)*real(rbarf) + imag(rbarf)*imag(rbarf);    
 
  fract = (Abar2*(1+ rbarf2 + (1 - rbarf2)*ratio))/(Abar2*(1+ rbarf2 + (1 - rbarf2)*ratio) + A2*(1+ rf2 + (1 - rf2)*ratio));  
  return; 
 
}
void EvtCPUtil::fractB0nonCP(EvtComplex Af, EvtComplex Abarf, 
                 EvtComplex Afbar, EvtComplex Abarfbar, 
                 double deltam, double beta, 
                 int flip, double &fract) {
 
//this function returns the number of B0 tags for decays into non-CP eigenstates
//(the "probB0" in the new EvtOtherB)
//this needs more thought... 
 
  //double gamma_B = EvtPDL::getWidth(B0);
  //report(INFO,"EvtGen") << "gamma " << gamma_B<< endl;
  //double xd = deltam/gamma_B;
 
  //why is the width of B0 0 in PDL??
 
  double xd = 0.65;
  double gamma_B = deltam/xd;
  double IAf, IAfbar, IAbarf, IAbarfbar;
  EvtComplex rf, rfbar, rbarf, rbarfbar;
  double rf2, rfbar2, rbarf2, rbarfbar2;
  double Af2, Afbar2, Abarf2, Abarfbar2;
 
  rf = EvtComplex(cos(2.0*beta),sin(2.0*beta))*Abarf/Af;
  rfbar = EvtComplex(cos(2.0*beta),sin(2.0*beta))*Abarfbar/Afbar; 
  rbarf = EvtComplex(cos(-2.0*beta),sin(-2.0*beta))*Af/Abarf;
  rbarfbar = EvtComplex(cos(-2.0*beta),sin(-2.0*beta))*Afbar/Abarfbar;
  
  
  rf2 = real(rf)*real(rf) + imag(rf)*imag(rf);
  rfbar2 = real(rfbar)*real(rfbar) + imag(rfbar)*imag(rfbar);
  rbarf2 = real(rbarf)*real(rbarf) + imag(rbarf)*imag(rbarf);
  rbarfbar2 = real(rbarfbar)*real(rbarfbar) + imag(rbarfbar)*imag(rbarfbar);
 
  Af2 = real(Af)*real(Af) + imag(Af)*imag(Af);
  Afbar2 = real(Afbar)*real(Afbar) + imag(Afbar)*imag(Afbar); 
  Abarf2 = real(Abarf)*real(Abarf) + imag(Abarf)*imag(Abarf);
  Abarfbar2 = real(Abarfbar)*real(Abarfbar) + imag(Abarfbar)*imag(Abarfbar);
 
 
//
//IAf = integral(gamma(B0->f)), etc.
//
 
  IAf = (Af2/(2*gamma_B))*(1+rf2+(1-rf2)/(1+xd*xd));
  IAfbar = (Afbar2/(2*gamma_B))*(1+rfbar2+(1-rfbar2)/(1+xd*xd));
  IAbarf = (Abarf2/(2*gamma_B))*(1+rbarf2+(1-rbarf2)/(1+xd*xd));
  IAbarfbar = (Abarfbar2/(2*gamma_B))*(1+rbarfbar2+(1-rbarfbar2)/(1+xd*xd));
  
//flip specifies the relative fraction of fbar events
 
  fract = IAbarf/(IAbarf+IAf) + flip*IAbarfbar/(IAfbar+IAbarfbar);
 
 
  return;  
} 
 
void EvtCPUtil::OtherB( EvtParticle *p,double &t, EvtId &otherb, double probB0){
 
  //Can not call this recursively!!!
  static int entryCount=0;
  entryCount++;
 
  //added by Lange Jan4,2000
  static EvtId B0B=EvtPDL::getId("anti-B0");
  static EvtId B0=EvtPDL::getId("B0");
 
  int isB0=EvtRandom::Flat(0.0,1.0)<probB0;
  
  int idaug;
  
  p->setLifetime();
  
  // now get the time between the decay of this B and the other B!
  
  EvtParticle *parent=p->getParent();
  
  EvtParticle *other;
  
  if (parent==0) {
    //report(ERROR,"EvtGen") << 
    //  "Warning CP violation with B having no parent!"<<endl;
    p->setLifetime();
    t=p->getLifetime();
    if (p->getId()==B0) otherb=B0B;
    if (p->getId()==B0B) otherb=B0;
    entryCount--;
    return;
  }
  else{
    if (parent->getDaug(0)!=p){
      other=parent->getDaug(0);
      idaug=0;
    }
    else{
      other=parent->getDaug(1);
      idaug=1;
    }
  }
  
  if (parent != 0 ) {
 
    //if (entryCount>1){
    //  report(INFO,"EvtGen") << "Double CP decay:"<<entryCount<<endl;
    //}
 
    //kludge!! Lange Mar21, 2003     
    // if the other B is an alias... don't change the flavor..   
    if ( other->getId().isAlias() ) {    
      OtherB(p,t,otherb);    
      entryCount--;
      return;    
      
    }
    
    if (entryCount==1){
    
      EvtVector4R p_init=other->getP4();
      //int decayed=other->getNDaug()>0;
      bool decayed = other->isDecayed();
 
      other->deleteTree();
    
      EvtScalarParticle* scalar_part;
      
      scalar_part=new EvtScalarParticle;
      if (isB0) {
    scalar_part->init(B0,p_init);
      }
      else{
    scalar_part->init(B0B,p_init);
      }
      other=(EvtParticle *)scalar_part;
      //    other->set_type(EvtSpinType::SCALAR);
      other->setDiagonalSpinDensity();      
    
      parent->insertDaugPtr(idaug,other);
    
      if (decayed){
    //report(INFO,"EvtGen") << "In CP Util calling decay \n";
    other->decay();
      }
 
    }
 
    otherb=other->getId();
 
    other->setLifetime();
    t=p->getLifetime()-other->getLifetime();
    
    otherb = other->getId();
    
  }
  else {
    report(INFO,"EvtGen") << "We have an error here!!!!"<<endl;
    otherb = EvtId(-1,-1); 
  }
  
  entryCount--;
  return ;
}
 
 
 
void EvtCPUtil::OtherB( EvtParticle *p,double &t, EvtId &otherb){
 
 
  static EvtId BSB=EvtPDL::getId("anti-B_s0");
  static EvtId BS0=EvtPDL::getId("B_s0");
  static EvtId B0B=EvtPDL::getId("anti-B0");
  static EvtId B0=EvtPDL::getId("B0");
  static EvtId UPS4=EvtPDL::getId("Upsilon(4S)");
 
  if (p->getId()==BS0||p->getId()==BSB){
    static double ctauL=EvtPDL::getctau(EvtPDL::getId("B_s0L"));
    static double ctauH=EvtPDL::getctau(EvtPDL::getId("B_s0H"));
    static double ctau=ctauL<ctauH?ctauH:ctauL;
    t=-log(EvtRandom::Flat())*ctau;
    EvtParticle* parent=p->getParent();
    if (parent!=0&&(parent->getId()==BS0||parent->getId()==BSB)){
      if (parent->getId()==BS0) otherb=BSB;
      if (parent->getId()==BSB) otherb=BS0;
      parent->setLifetime(t);
      return;
    }
    if (p->getId()==BS0) otherb=BSB;
    if (p->getId()==BSB) otherb=BS0;
    p->setLifetime(t);
    return;
  }
 
 
 
  
   p->setLifetime();
 
 
// now get the time between the decay of this B and the other B!
  
  EvtParticle *parent=p->getParent();
 
  if (parent==0||parent->getId()!=UPS4) {
    //report(ERROR,"EvtGen") << 
    //  "Warning CP violation with B having no parent!"<<endl;
    t=p->getLifetime();
    if (p->getId()==B0) otherb=B0B;
    if (p->getId()==B0B) otherb=B0;
    if (p->getId()==BS0) otherb=BSB;
    if (p->getId()==BSB) otherb=BS0;
    return;
  }
  else{
    if (parent->getDaug(0)!=p){
      otherb=parent->getDaug(0)->getId();
      parent->getDaug(0)->setLifetime();
      t=p->getLifetime()-parent->getDaug(0)->getLifetime();
    }
    else{
     otherb=parent->getDaug(1)->getId();
      parent->getDaug(1)->setLifetime();
      t=p->getLifetime()-parent->getDaug(1)->getLifetime();
   }
  }
 
 
  return ;
}
 
 
void EvtCPUtil::incoherentMix(const EvtId id, double &t, int &mix){
 
  int stdHepNum=EvtPDL::getStdHep(id);
  stdHepNum=abs(stdHepNum);
  
  EvtId partId=EvtPDL::evtIdFromStdHep(stdHepNum);
 
  std::string partName=EvtPDL::name(partId);
  std::string hname=partName+std::string("H");
  std::string lname=partName+std::string("L");
 
  EvtId lId=EvtPDL::getId(lname);
  EvtId hId=EvtPDL::getId(hname);
 
  double ctauL=EvtPDL::getctau(lId);
  double ctauH=EvtPDL::getctau(hId);
  double ctau=0.5*(ctauL+ctauH);
  double y=(ctauH-ctauL)/ctau;
 
  //need to figure out how to get these parameters into the code...
 
  std::string qoverpParmName=std::string("qoverp_incohMix_")+partName;
  std::string mdParmName=std::string("dm_incohMix_")+partName;
  int ierr;
  double qoverp=atof(EvtSymTable::Get(qoverpParmName,ierr).c_str());
  double x=atof(EvtSymTable::Get(mdParmName,ierr).c_str())*ctau/EvtConst::c;
  double fac;
 
  if(id==partId){
    fac=1.0/(qoverp*qoverp);
  }
  else{
    fac=qoverp*qoverp;
  }
 
  double mixprob=(x*x+y*y)/(x*x+y*y+fac*(2+x*x-y*y));
 
  int mixsign;
 
  mixsign=(mixprob>EvtRandom::Flat(0.0,1.0))?-1:1;
 
  double prob;
 
  do{
    t=-log(EvtRandom::Flat())*ctauL;
    prob=1+exp(y*t/ctau)+mixsign*2*exp(0.5*y*t/ctau)*cos(x*t);
  }while(prob<4*EvtRandom::Flat());
 
  mix=0;
 
  if (mixsign==-1) mix=1;
   
  return;
}