EvtKstarnunu.cc

Go to the documentation of this file.

//--------------------------------------------------------------------------
//
// 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: EvtKstarnunu.cc
//
// Description: B ==> K* nu nubar
//
// Modification history:
//
//    RYD     September 29, 1997        Module created
//
//------------------------------------------------------------------------
//
// Package:     EVT
// Module:      EvtKstarnunu
//
//
// Implementation:
//
//
// Author:      RYD
// Created:     Sept. 29 1997
//
//
#include "EvtKstarnunu.hh"
#include "../EvtGenBase/EvtDiracSpinor.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <iostream>
#include <stdlib.h>
#include <string>
 
EvtKstarnunu::~EvtKstarnunu() {}
 
void EvtKstarnunu::getName( std::string& model_name ) { model_name = "KSTARNUNU"; }
 
EvtDecayBase* EvtKstarnunu::clone() { return new EvtKstarnunu; }
 
void EvtKstarnunu::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 3 );
 
  // We expect the parent to be a scalar
  // and the daughters to be K neutrino netrino
 
  checkSpinParent( EvtSpinType::SCALAR );
 
  checkSpinDaughter( 0, EvtSpinType::VECTOR );
  checkSpinDaughter( 1, EvtSpinType::NEUTRINO );
  checkSpinDaughter( 2, EvtSpinType::NEUTRINO );
}
 
void EvtKstarnunu::decay( EvtParticle* p ) {
 
  static EvtId NUE  = EvtPDL::getId( "nu_e" );
  static EvtId NUM  = EvtPDL::getId( "nu_mu" );
  static EvtId NUT  = EvtPDL::getId( "nu_tau" );
  static EvtId NUEB = EvtPDL::getId( "anti-nu_e" );
  static EvtId NUMB = EvtPDL::getId( "anti-nu_mu" );
  static EvtId NUTB = EvtPDL::getId( "anti-nu_tau" );
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  double m_b = p->mass();
 
  EvtParticle *meson, *neutrino1, *neutrino2;
  meson                = p->getDaug( 0 );
  neutrino1            = p->getDaug( 1 );
  neutrino2            = p->getDaug( 2 );
  EvtVector4R momnu1   = neutrino1->getP4();
  EvtVector4R momnu2   = neutrino2->getP4();
  EvtVector4R momkstar = meson->getP4();
 
  double v0_0, a0_0, a1_0, a2_0;
  double m2v0, m2a0, a1_b, a2_b;
  v0_0 = 0.47;
  a0_0 = 0.30;
  a1_0 = 0.37;
  a2_0 = 0.40;
  m2v0 = 5. * 5.;
  m2a0 = 4.8 * 4.8;
  a1_b = -0.023;
  a2_b = 0.034;
 
  EvtVector4R q  = momnu1 + momnu2;
  double      q2 = q.mass2();
 
  double v0, a1, a2;
  v0 = v0_0 / ( 1 - q2 / m2v0 );
  a1 = a1_0 * ( 1 + a1_b * q2 );
  a2 = a2_0 * ( 1 + a2_b * q2 );
 
  EvtVector4R p4b;
  p4b.set( m_b, 0., 0., 0. ); // Do calcs in mother rest frame
 
  double m_k = meson->mass();
 
  EvtTensor4C tds =
      ( -2 * v0 / ( m_b + m_k ) ) * dual( directProd( p4b, momkstar ) ) -
      EvtComplex( 0.0, 1.0 ) *
          ( ( m_b + m_k ) * a1 * EvtTensor4C::g() -
            ( a2 / ( m_b + m_k ) ) * directProd( p4b - momkstar, p4b + momkstar ) );
 
  EvtVector4C l;
 
  if ( getDaug( 1 ) == NUE || getDaug( 1 ) == NUM || getDaug( 1 ) == NUT )
  { l = EvtLeptonVACurrent( neutrino1->spParentNeutrino(), neutrino2->spParentNeutrino() ); }
  if ( getDaug( 1 ) == NUEB || getDaug( 1 ) == NUMB || getDaug( 1 ) == NUTB )
  { l = EvtLeptonVACurrent( neutrino2->spParentNeutrino(), neutrino1->spParentNeutrino() ); }
 
  EvtVector4C et0, et1, et2;
  et0 = tds.cont1( meson->epsParent( 0 ).conj() );
  et1 = tds.cont1( meson->epsParent( 1 ).conj() );
  et2 = tds.cont1( meson->epsParent( 2 ).conj() );
 
  vertex( 0, l * et0 );
  vertex( 1, l * et1 );
  vertex( 2, l * et2 );
 
  return;
}