deformednucleus.cc

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/*
 *    Copyright (c) 2014-2019
 *      SMASH Team
 *
 *    GNU General Public License (GPLv3 or later)
 */
#include "smash/deformednucleus.h"

#include <cmath>
#include <stdexcept>

#include "smash/angles.h"
#include "smash/configuration.h"
#include "smash/constants.h"
#include "smash/fourvector.h"
#include "smash/particledata.h"
#include "smash/random.h"
#include "smash/threevector.h"

namespace smash {

// For readability and layout issues parts of the customnucleus userguide
// needs to be located here. The example configuration can however be found in
// customnucleus.cc

DeformedNucleus::DeformedNucleus(const std::map<PdgCode, int> &particle_list,
                                 int nTest)
    : Nucleus(particle_list, nTest) {}

DeformedNucleus::DeformedNucleus(Configuration &config, int nTest)
    : Nucleus(config, nTest) {
  if (config.has_value({"Deformed", "Automatic"}) &&
      config.take({"Deformed", "Automatic"})) {
    set_deformation_parameters_automatic();
  } else {
    set_deformation_parameters_from_config(config);
  }
}

double DeformedNucleus::deformed_woods_saxon(double r, double cosx) const {
  return Nucleus::get_saturation_density() /
         (1 + std::exp((r - Nucleus::get_nuclear_radius() *
                                (1 + beta2_ * y_l_0(2, cosx) +
                                 beta4_ * y_l_0(4, cosx))) /
                       Nucleus::get_diffusiveness()));
}

ThreeVector DeformedNucleus::distribute_nucleon() {
  double a_radius;
  Angles a_direction;
  // Set a sensible maximum bound for radial sampling.
  double radius_max =
      Nucleus::get_nuclear_radius() / Nucleus::get_diffusiveness() +
      Nucleus::get_nuclear_radius() * Nucleus::get_diffusiveness();

  // Sample the distribution.
  do {
    a_direction.distribute_isotropically();
    // sample r**2 dr
    a_radius = radius_max * std::cbrt(random::canonical());
  } while (random::canonical() >
           deformed_woods_saxon(a_radius, a_direction.costheta()) /
               Nucleus::get_saturation_density());

  // Update (x, y, z) positions.
  return a_direction.threevec() * a_radius;
}

void DeformedNucleus::set_deformation_parameters_automatic() {
  // Set the deformation parameters extracted from \iref{Moller:1993ed}.
  switch (Nucleus::number_of_particles()) {
    case 238:  // Uranium
      set_beta_2(0.28);
      set_beta_4(0.093);
      break;
    case 208:  // Lead
      set_beta_2(0.0);
      set_beta_4(0.0);
      break;
    case 197:  // Gold
      set_beta_2(-0.131);
      set_beta_4(-0.031);
      break;
    case 63:  // Copper
      set_beta_2(0.162);
      set_beta_4(-0.006);
      break;
    default:
      throw std::domain_error(
          "Mass number not listed for automatically setting deformation "
          "parameters. Please specify at least \"Beta_2\" and \"Beta_4\" "
          "manually and set \"Automatic: False.\" ");
  }

  // Set a random nuclear rotation.
  nuclear_orientation_.distribute_isotropically();
}

void DeformedNucleus::set_deformation_parameters_from_config(
    Configuration &config) {
  // Deformation parameters.
  if (config.has_value({"Deformed", "Beta_2"})) {
    set_beta_2(static_cast<double>(config.take({"Deformed", "Beta_2"})));
  }
  if (config.has_value({"Deformed", "Beta_4"})) {
    set_beta_4(static_cast<double>(config.take({"Deformed", "Beta_4"})));
  }
  if (config.has_value({"Deformed", "Theta"})) {
    set_polar_angle(static_cast<double>(config.take({"Deformed", "Theta"})));
  }
  if (config.has_value({"Deformed", "Phi"})) {
    set_azimuthal_angle(static_cast<double>(config.take({"Deformed", "Phi"})));
  }
}

void DeformedNucleus::rotate() {
  for (auto &particle : *this) {
    /* Rotate every vector by the nuclear azimuth phi and polar angle
     * theta (the Euler angles). This means applying the matrix for a
     * rotation of phi about z, followed by the matrix for a rotation
     * theta about the rotated x axis. The third angle psi is 0 by symmetry.*/
    ThreeVector three_pos = particle.position().threevec();
    three_pos.rotate(nuclear_orientation_.phi(), nuclear_orientation_.theta(),
                     0.);
    particle.set_3position(three_pos);
  }
}

void DeformedNucleus::generate_fermi_momenta() {
  throw std::domain_error(
      "Fermi momenta currently not implemented"
      " for a deformed nucleus.");
}

double DeformedNucleus::y_l_0(int l, double cosx) const {
  if (l == 2) {
    return (1. / 4) * std::sqrt(5 / M_PI) * (3. * (cosx * cosx) - 1);
  } else if (l == 4) {
    return (3. / 16) * std::sqrt(1 / M_PI) *
           (35. * (cosx * cosx) * (cosx * cosx) - 30. * (cosx * cosx) + 3);
  } else {
    throw std::domain_error(
        "Not a valid angular momentum quantum number in"
        "DeformedNucleus::y_l_0.");
  }
}

}  // namespace smash