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EvtHQET2FF.cpp
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EvtHQET2FF.cpp
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/***********************************************************************
* Copyright 1998-2020 CERN for the benefit of the EvtGen authors *
* *
* This file is part of EvtGen. *
* *
* EvtGen is free software: you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation, either version 3 of the License, or *
* (at your option) any later version. *
* *
* EvtGen is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with EvtGen. If not, see <https://www.gnu.org/licenses/>. *
***********************************************************************/
#include "EvtGenModels/EvtHQET2FF.hh"
#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtReport.hh"
#include <math.h>
#include <stdlib.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;
extended = false;
}
EvtHQET2FF::EvtHQET2FF( double hqetrho2, double hqetha1_1, double hqetr1_1,
double hqetr2_1, double hqetr0_1 )
{
rho2 = hqetrho2;
r0_1 = hqetr0_1;
r1_1 = hqetr1_1;
r2_1 = hqetr2_1;
ha1_1 = hqetha1_1;
extended = true;
}
EvtHQET2FF::EvtHQET2FF( double hqetrho2, double hqetv1_1 )
{
rho2 = hqetrho2;
v1_1 = hqetv1_1;
extended = false;
}
EvtHQET2FF::EvtHQET2FF( double hqetrho2, double hqetv1_1, double indelta )
{
rho2 = hqetrho2;
v1_1 = hqetv1_1;
delta = indelta;
extended = true;
}
void EvtHQET2FF::getscalarff( EvtId parent, EvtId, 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 dispersion 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;
if ( extended ) {
//if in extended mode, use helicity-suppressed FF using the result from
//Tanaka and Watanabe, Phys. Rev. D 82 034027 (2010)
double r = mass / mb;
double r1 = r + 1.0;
double s1 = v1 * ( 1 + delta * ( -0.019 + 0.041 * ( w - 1 ) -
0.015 * ( w - 1 ) *
( w - 1 ) ) ); //as in ref
*f0m = s1 * ( w + 1.0 ) * 2.0 * r /
( r1 * r1 ); //convert to convention used by EvtGen with proper relative normalization
}
}
void EvtHQET2FF::getvectorff( EvtId parent, EvtId, 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 dispersion 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;
if ( extended ) {
// Here we use the expectation for R_0(w) from
// Fajfer et al, Phys. Rev. D 85 094025 (2012)
double r0 = r0_1 - 0.11 * ( w - 1 ) + 0.01 * ( w - 1 ) * ( w - 1 );
*a0f = ( r0 / rstar ) * ha1;
}
}
void EvtHQET2FF::gettensorff( EvtId, EvtId, double, double, double*, double*,
double*, double* )
{
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< "Not implemented :gettensorff in EvtHQET2FF.\n";
::abort();
}
void EvtHQET2FF::getbaryonff( EvtId, EvtId, double, double, double*, double*,
double*, double* )
{
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< "Not implemented :getbaryonff in EvtHQET2FF.\n";
::abort();
}
void EvtHQET2FF::getdiracff( EvtId, EvtId, double, double, double*, double*,
double*, double*, double*, double* )
{
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< "Not implemented :getdiracff in EvtHQET2FF.\n";
::abort();
}
void EvtHQET2FF::getraritaff( EvtId, EvtId, double, double, double*, double*,
double*, double*, double*, double*, double*,
double* )
{
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< "Not implemented :getraritaff in EvtHQET2FF.\n";
::abort();
}

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