FlatTransferFunctionOnP.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 <momemta/Types.h>
#include <momemta/Math.h>

class FlatTransferFunctionOnP: public Module {
    public:

        FlatTransferFunctionOnP(PoolPtr pool, const ParameterSet& parameters): Module(pool, parameters.getModuleName()) {
            m_ps_point = get<double>(parameters.get<InputTag>("ps_point"));
            m_input = get<LorentzVector>(parameters.get<InputTag>("reco_particle"));

            m_PMin = parameters.get<double>("min");
            m_PMax = parameters.get<double>("max");
        };

        virtual Status work() override {

            const double& ps_point = *m_ps_point;
            const LorentzVector& reco_particle = *m_input;

            const double range = m_PMax - m_PMin;
            const double gen_P = m_PMin + range*ps_point;

            // To change the particle's |P| without changing its direction and mass:
            double gen_E = sqrt(SQ(gen_P) + SQ(reco_particle.M()));
            output->SetCoordinates(
                gen_P * std::sin(reco_particle.Theta()) * std::cos(reco_particle.Phi()),
                gen_P * std::sin(reco_particle.Theta()) * std::sin(reco_particle.Phi()),
                gen_P * std::cos(reco_particle.Theta()),
                gen_E);

            // Compute TF*jacobian, ie the jacobian of the transformation of [0,1]->[range_min,range_max]
            *TF_times_jacobian = range;

            return Status::OK;
        }

    private:

        double m_PMin, m_PMax;

        // Inputs
        Value<double> m_ps_point;
        Value<LorentzVector> m_input;

        // Outputs
        std::shared_ptr<LorentzVector> output = produce<LorentzVector>("output");
        std::shared_ptr<double> TF_times_jacobian = produce<double>("TF_times_jacobian");
};

REGISTER_MODULE(FlatTransferFunctionOnP)
        .Input("ps_point")
        .Input("reco_particle")
        .Output("output")
        .Output("TF_times_jacobian")
        .Attr("min:double")
        .Attr("max:double");