decayaction.h

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/*
 *
 *    Copyright (c) 2015-2020,2025
 *      SMASH Team
 *
 *    GNU General Public License (GPLv3 or later)
 *
 */
 
#ifndef SRC_INCLUDE_SMASH_DECAYACTION_H_
#define SRC_INCLUDE_SMASH_DECAYACTION_H_
 
#include <optional>
#include <utility>
 
#include "action.h"
 
namespace smash {
 
class DecayAction : public Action {
 public:
  DecayAction(
      const ParticleData& p, double time,
      SpinInteractionType spin_interaction_type = SpinInteractionType::Off);
 
  void add_decays(DecayBranchList pv);
 
  void add_decay(DecayBranchPtr p);
 
  void generate_final_state() override;
 
  std::pair<double, double> sample_masses(
      double kinetic_energy_cm) const override;
 
  void sample_2body_phasespace() override;
 
  double get_total_weight() const override { return total_width_; }
 
  double get_partial_weight() const override { return partial_width_; }
 
  double total_width() const { return total_width_; }
 
  class InvalidDecay : public std::invalid_argument {
    using std::invalid_argument::invalid_argument;
  };
 
 private:
  std::optional<bool> was_2body_phase_space_sampled_with_potentials_as_valid_ =
      std::nullopt;
 
  static inline bool is_sigmastar_to_lambda_pion_decay(
      const ParticleData& parent, const ParticleData& daughter0,
      const ParticleData& daughter1, int& lambda_idx, int& pion_idx) {
    // Fast rejections first
    if (!parent.is_sigmastar())
      return false;
 
    const bool lambda0 = daughter0.pdgcode().is_Lambda();
    const bool lambda1 = daughter1.pdgcode().is_Lambda();
    const bool pion0 = daughter0.pdgcode().is_pion();
    const bool pion1 = daughter1.pdgcode().is_pion();
 
    // Check if one daughter is a lambda and the other a pion
    if (lambda0 && pion1 && !lambda1 && !pion0) {
      lambda_idx = 0;
      pion_idx = 1;
      return true;
    } else if (lambda1 && pion0 && !lambda0 && !pion1) {
      lambda_idx = 1;
      pion_idx = 0;
      return true;
    } else {
      return false;
    }
  }
 
 protected:
  void format_debug_output(std::ostream& out) const override;
 
  bool sample_outgoing_particles();
 
  DecayBranchList decay_channels_;
 
  double total_width_;
 
  double partial_width_;
 
  int L_ = 0;
 
 private:
  SpinInteractionType spin_interaction_type_;
};
 
}  // namespace smash
 
#endif  // SRC_INCLUDE_SMASH_DECAYACTION_H_