FFBtoD0starLLSW.cc

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///
/// @file  FFBtoD0starLLSW.cc
/// @brief \f$ B \rightarrow D_0^* \f$ LLSW form factors
///

//**** This file is a part of the HAMMER library
//**** Copyright (C) 2016 - 2020 The HAMMER Collaboration
//**** HAMMER is licensed under version 3 of the GPL; see COPYING for details
//**** Please note the MCnet academic guidelines; see GUIDELINES for details

// -*- C++ -*-
#include "Hammer/FormFactors/FFBtoD0starLLSW.hh"
#include "Hammer/IndexLabels.hh"
#include "Hammer/Math/Constants.hh"
#include "Hammer/Math/Utils.hh"
#include "Hammer/Particle.hh"
#include "Hammer/Tools/Pdg.hh"
#include "Hammer/Math/MultiDim/SparseContainer.hh"
#include <cmath>
#include <iostream>

using namespace std;

namespace Hammer {

    namespace MD = MultiDimensional;

    FFBtoD0starLLSW::FFBtoD0starLLSW() {
        // Create tensor rank and dimensions
        vector<IndexType> dims = {4};
        setGroup("LLSW"); //override BLPR base class FF group setting
        string name{"FFBtoD0starLLSW"};
        
        setPrefix("BtoD**0*");
        addProcessSignature(PID::BPLUS, {-PID::DSSD0STAR});
        addTensor(Tensor{name, MD::makeEmptySparse(dims, {FF_BDSSD0STAR})});

        addProcessSignature(PID::BZERO, {PID::DSSD0STARMINUS});
        addTensor(Tensor{name, MD::makeEmptySparse(dims, {FF_BDSSD0STAR})});

        setPrefix("BstoDs**0*");
        addProcessSignature(PID::BS, {PID::DSSDS0STARMINUS});
        addTensor(Tensor{name, MD::makeEmptySparse(dims, {FF_BSDSSDS0STAR})});
        
        setSignatureIndex();
    }

    void FFBtoD0starLLSW::defineSettings() {
        //_FFErrNames = ;
        setPath(getFFErrPrefixGroup().get());
        setUnits("GeV");

        //Pole mass scheme as in EvtGen
        addSetting<double>("mb",4.2);
        addSetting<double>("mc",1.4);
        addSetting<double>("zt1", 0.68);
        addSetting<double>("ztp", -0.2);
        addSetting<double>("zeta1", 0.3);
        addSetting<double>("chi1", 0.);
        addSetting<double>("chi2", 0.);
        addSetting<double>("laB", 0.4);
        addSetting<double>("laS", 0.76);

        initialized = true;
    }

    void FFBtoD0starLLSW::evalAtPSPoint(const vector<double>& point, const vector<double>& masses) {
        Tensor& result = getTensor();
        result.clearData();

        if(!initialized){
            MSG_WARNING("Warning, Setting have not been defined!");
        }

        double Mb = 0.;
        double Mc = 0.;
        // double unitres = 1.;
        if(masses.size() >= 2) {
            Mb = masses[0];
            Mc = masses[1];
            //unitres = _units;
        }
        else {
            Mb = this->masses()[0];
            Mc = this->masses()[1];
        }
        const double Mb2 = Mb*Mb;
        const double Mc2 = Mc*Mc;

        double Sqq = point[0];

        // const double sqSqq = sqrt(Sqq);
        double w = (Mb2 + Mc2 - Sqq)/(2.*Mb*Mc);
        //safety measure if w==1.0
        if(isZero(w - 1.0)) w += 1e-6;

        //LLSW parameters
        // const double zBC = (*getSetting<double>("mc"))/(*getSetting<double>("mb"));
        const double eB = 1./(*getSetting<double>("mb")*2.);
        const double eC = 1./(*getSetting<double>("mc")*2.);
        const double zt1 = (*getSetting<double>("zt1"));
        const double ztp = (*getSetting<double>("ztp"));
        const double zeta1 = (*getSetting<double>("zeta1"));
        const double chi1 = (*getSetting<double>("chi1"));
        const double chi2 = (*getSetting<double>("chi2"));
        const double laB = (*getSetting<double>("laB"));
        const double laS = (*getSetting<double>("laS"));

        const double LambdaD12 = -laB + laS*w;
        const double Gb = (-(laB*(2 + w)) + laS*(1 + 2*w))/(1 + w) - 2*(w-1)*zeta1;
        const double LOIWzeta = zt1 + (w-1)*ztp;

        //Form factors
        const double gp = -(eC*((3*LambdaD12)/(1 + w) - 2*(w-1)*zeta1)) - eB*Gb;
        const double gm = 1 + eC*(6*chi1 - 2*(1 + w)*chi2);


        //Set elements
        result.element({1}) = gp;
        result.element({2}) = gm;

        result *= LOIWzeta;

    }

    std::unique_ptr<FormFactorBase> FFBtoD0starLLSW::clone(const std::string& label) {
        MAKE_CLONE(FFBtoD0starLLSW, label);
    }

} // namespace Hammer