HelicityFormalism.h

Go to the documentation of this file.

/*  YAP - Yet another PWA toolkit
    Copyright 2015, Technische Universitaet Muenchen,
    Authors: Daniel Greenwald, Johannes Rauch

    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/>.
*/


#ifndef yap_HelicityFormalism_h
#define yap_HelicityFormalism_h

#include "fwd/DataPoint.h"
#include "fwd/Model.h"
#include "fwd/ParticleCombination.h"
#include "fwd/Spin.h"

#include "RequiresHelicityAngles.h"
#include "SpinAmplitude.h"
#include "SpinAmplitudeCache.h"

#include <complex>
#include <map>
#include <memory>

namespace yap {

class HelicitySpinAmplitude : public SpinAmplitude, public RequiresHelicityAngles
{
protected:

    HelicitySpinAmplitude(Model& m, unsigned two_J, const SpinVector& two_j, unsigned l, unsigned two_s);

public:

    virtual const std::complex<double> amplitude(const DataPoint& d, const std::shared_ptr<ParticleCombination>& pc,
                                         int two_M, const SpinProjectionVector& two_m) const override
    { return (initialTwoJ() == 0) ? Coefficients_.at(two_m) : SpinAmplitude::amplitude(d, pc, two_M, two_m); }

    virtual void calculate(DataPoint& d, StatusManager& sm) const override
    { if (initialTwoJ() != 0) SpinAmplitude::calculate(d, sm); }

    virtual const std::complex<double> calc(int two_M, const SpinProjectionVector& two_m,
                                            const DataPoint& d, const std::shared_ptr<ParticleCombination>& pc) const override;

    virtual bool equals(const SpinAmplitude& other) const override
    { return dynamic_cast<const HelicitySpinAmplitude*>(&other) and SpinAmplitude::equals(other); }

    virtual std::string formalism() const override
    { return "helicity formalism"; }

    friend class HelicityFormalism;

private:

    std::map<SpinProjectionVector, double> Coefficients_;

};

class HelicityFormalism : public SpinAmplitudeCache
{
public:

    HelicityFormalism() : SpinAmplitudeCache() {}

private:

    virtual std::shared_ptr<SpinAmplitude> create(Model& m, unsigned two_J, const SpinVector& two_j, unsigned l, unsigned two_s) const override
    { return std::shared_ptr<SpinAmplitude>(new HelicitySpinAmplitude(m, two_J, two_j, l, two_s)); }

};

}

#endif