NarrowWidthApproximation.cc

/*
 *  MoMEMta: a modular implementation of the Matrix Element Method
 *  Copyright (C) 2016  Universite catholique de Louvain (UCL), Belgium
 *
 *  This program 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.
 *
 *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <momemta/ParameterSet.h>
#include <momemta/Module.h>

#include <cmath>

class NarrowWidthApproximation: public Module {
    public:

        NarrowWidthApproximation(PoolPtr pool, const ParameterSet& parameters): Module(pool, parameters.getModuleName())
        {
            double mass = parameters.get<double>("mass");
            double width = parameters.get<double>("width");

            *jacobian = M_PI;
            if(parameters.get<bool>("propagator_in_me", true))
                *jacobian *= mass*width;
            else
                *jacobian /= mass*width;

            *s = mass*mass;
        }

    private:

        std::shared_ptr<double> s = produce<double>("s");
        std::shared_ptr<double> jacobian = produce<double>("jacobian");
};

REGISTER_MODULE(NarrowWidthApproximation)
        .Output("s")
        .Output("jacobian")
        .Attr("mass:double")
        .Attr("width:double")
        .Attr("propagator_in_me:bool=true");