EvtHQET2FF.cc

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//--------------------------------------------------------------------------
//
// Module: EvtHQET2FF.cc
//
// Description: form factors for B->D*lnu & B->Dlnu according to HQET
//              with dispersive FF
//
// Modification history:
//
//    Marco Bomben     March 10, 2003        Module created
//
//------------------------------------------------------------------------
//
#include "EvtHQET2FF.hh"
#include "../EvtGenBase/EvtId.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include <math.h>
#include <string>
 
EvtHQET2FF::EvtHQET2FF( double hqetrho2, double hqetha1_1, double hqetr1_1, double hqetr2_1 ) {
 
  rho2  = hqetrho2;
  r1_1  = hqetr1_1;
  r2_1  = hqetr2_1;
  ha1_1 = hqetha1_1;
 
  return;
}
 
EvtHQET2FF::EvtHQET2FF( double hqetrho2, double hqetv1_1 ) {
 
  rho2 = hqetrho2;
  v1_1 = hqetv1_1;
 
  return;
}
 
void EvtHQET2FF::getscalarff( EvtId parent, EvtId daught, double t, double mass, double* f0p,
                              double* f0m ) {
 
  double mb = EvtPDL::getMeanMass( parent );
  double w  = ( ( mb * mb ) + ( mass * mass ) - t ) / ( 2.0 * mb * mass );
 
  // Form factors have a general form, with parameters passed in
  // from the arguements.
 
  // Use disparsion relation parametrization from
  // I.Caprini, L.Lelluch, M.Neubert, Nucl. Phys. B 530,153(1998)
  const double z  = ( sqrt( w + 1 ) - sqrt( 2. ) ) / ( sqrt( w + 1 ) + sqrt( 2. ) );
  double       v1 = v1_1 * ( 1. - 8. * rho2 * z + ( 51. * rho2 - 10. ) * z * z -
                       ( 252. * rho2 - 84. ) * z * z * z );
 
  *f0p = v1;
  *f0m = 0.0;
 
  return;
}
 
void EvtHQET2FF::getvectorff( EvtId parent, EvtId daught, double t, double mass, double* a1f,
                              double* a2f, double* vf, double* a0f ) {
 
  double mb = EvtPDL::getMeanMass( parent );
  double w  = ( ( mb * mb ) + ( mass * mass ) - t ) / ( 2.0 * mb * mass );
 
  // Form factors have a general form, with parameters passed in
  // from the arguements.
 
  double rstar = ( 2.0 * sqrt( mb * mass ) ) / ( mb + mass );
 
  // Use disparsion relation parametrization from
  // I.Caprini, L.Lelluch, M.Neubert, Nucl. Phys. B 530,153(1998)
  const double z   = ( sqrt( w + 1 ) - sqrt( 2. ) ) / ( sqrt( w + 1 ) + sqrt( 2. ) );
  double       ha1 = ha1_1 * ( 1. - 8. * rho2 * z + ( 53. * rho2 - 15. ) * z * z -
                         ( 231. * rho2 - 91. ) * z * z * z );
  double       r1  = r1_1 - 0.12 * ( w - 1 ) + 0.05 * ( w - 1 ) * ( w - 1 );
  double       r2  = r2_1 + 0.11 * ( w - 1 ) - 0.06 * ( w - 1 ) * ( w - 1 );
  ;
 
  *a1f = ( 1.0 - ( t / ( ( mb + mass ) * ( mb + mass ) ) ) ) * ha1;
  *a1f = ( *a1f ) / rstar;
  *a2f = ( r2 / rstar ) * ha1;
  *vf  = ( r1 / rstar ) * ha1;
  *a0f = 0.0;
 
  return;
}