Highland.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2018-2020 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once

#include "Acts/Material/Interactions.hpp"
#include "ActsFatras/Physics/Scattering/detail/Scattering.hpp"

#include <random>

namespace ActsFatras {
namespace detail {

struct Highland {
  template <typename generator_t>
  double operator()(generator_t &generator, const Acts::MaterialSlab &slab,
                    Particle &particle) const {
    // compute the planar scattering angle
    const auto theta0 = Acts::computeMultipleScatteringTheta0(
        slab, particle.pdg(), particle.mass(),
        particle.charge() / particle.absMomentum(), particle.charge());
    // draw from the normal distribution representing the 3d angle distribution
    return std::normal_distribution<double>(0.0, M_SQRT2 * theta0)(generator);
  }
};

}  // namespace detail

using HighlandScattering = detail::Scattering<detail::Highland>;

}  // namespace ActsFatras