ResonanceObject.h

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2022-2024  Laurent Forthomme
 *
 *  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
 *  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 CepGen_Physics_ResonanceObject_h
#define CepGen_Physics_ResonanceObject_h
 
#include "CepGen/Core/SteeredObject.h"
 
namespace cepgen {
  class ResonanceObject : public SteeredObject<ResonanceObject> {
  public:
    explicit ResonanceObject(const ParametersList&);
 
    static ParametersDescription description();
 
    struct KinematicsBlock {
      explicit KinematicsBlock(double w2, double q2, double mp2, double mpi2, double meta2);
      static inline double mom(double energy, double mass2) { return std::sqrt(std::max(0., energy * energy - mass2)); }
      const double w2, w;
      const double q2;
      // equivalent photon energy-momentum
      const double k, kcm;
      const double ppicm;   
      const double ppi2cm;  
      const double petacm;  
    };
 
  protected:
    inline double kr() const { return 0.5 * (mass_ * mass_ - mp2_) / mp_; }
    inline double pcmr(double m2) const { return KinematicsBlock::mom(ecmr(m2), m2); }
    double ecmr(double m2) const;
    inline double kcmr() const { return ecmr(0.); }
    double partialWidth(const KinematicsBlock&) const;  
    double photonWidth(const KinematicsBlock&) const;   
 
    const struct BranchingRatios : SteeredObject<BranchingRatios> {
      explicit BranchingRatios(const ParametersList&);
 
      static ParametersDescription description();
 
      inline bool valid() const { return singlepi + doublepi + eta == 1.; }
 
      double singlepi;  
      double doublepi;  
      double eta;       
    } br_;
    const int ang_mom_;   
    const double x0_;     
    const double mass_;   
    const double width_;  
    const double mp_;     
    const double mp2_;    
    const double mpi2_;   
    const double meta2_;  
    const double x02_;    
  };
}  // namespace cepgen
 
#endif