PartonicParameterisation.h

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2023  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/>.
 */
 
#include <array>
 
#include "CepGen/StructureFunctions/Parameterisation.h"
 
namespace cepgen {
  namespace strfun {
    class PartonicParameterisation : public Parameterisation {
    public:
      explicit PartonicParameterisation(const ParametersList&);
      virtual ~PartonicParameterisation() = default;
 
      enum class Mode { full = 0, valence = 1, sea = 2 };
      friend std::ostream& operator<<(std::ostream&, const Mode& mode);
 
      static ParametersDescription description();
      void eval() override final;
 
    protected:
      virtual double evalxQ2(int flavour, double xbj, double q2) = 0;
      const unsigned short num_flavours_;
      const Mode mode_;
 
      static constexpr std::array<short, 6> QUARK_PDGS = {{1, 2, 3, 4, 5, 6}};
      static constexpr std::array<short, 6> Q_TIMES_3 = {{
          -1 /*d*/, 2 /*u*/, -1 /*s*/, 2 /*c*/, -1 /*b*/, 2 /*t*/
      }};
    };
  }  // namespace strfun
}  // namespace cepgen