Hit.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 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 <cstdint>

#include "Acts/Geometry/GeometryID.hpp"
#include "Acts/Utilities/Definitions.hpp"
#include "ActsFatras/EventData/Barcode.hpp"

namespace ActsFatras {

class Hit {
 public:
  using Scalar = double;
  using Vector4 = Acts::ActsVector<Scalar, 4>;
  using Vector3 = Acts::ActsVector<Scalar, 3>;

  Hit() = default;
  template <typename Position4, typename Momentum40, typename Momentum41>
  Hit(Acts::GeometryID geometryId, Barcode particleId,
      const Eigen::MatrixBase<Position4>& pos4,
      const Eigen::MatrixBase<Momentum40>& before4,
      const Eigen::MatrixBase<Momentum41>& after4, int32_t index_ = -1)
      : m_geometryId(geometryId),
        m_particleId(particleId),
        m_index(index_),
        m_pos4(pos4),
        m_before4(before4),
        m_after4(after4) {}
  Hit(const Hit&) = default;
  Hit(Hit&&) = default;
  Hit& operator=(const Hit&) = default;
  Hit& operator=(Hit&&) = default;

  constexpr Acts::GeometryID geometryId() const { return m_geometryId; }
  constexpr Barcode particleId() const { return m_particleId; }
  constexpr int32_t index() const { return m_index; }

  const Vector4& position4() const { return m_pos4; }
  auto position() const { return m_pos4.head<3>(); }
  Scalar time() const { return m_pos4[3]; }

  const Vector4& momentum4Before() const { return m_before4; }
  const Vector4& momentum4After() const { return m_after4; }
  Vector3 unitDirectionBefore() const {
    return m_before4.head<3>().normalized();
  }
  Vector3 unitDirectionAfter() const { return m_after4.head<3>().normalized(); }
  Vector3 unitDirection() const {
    auto dir0 = m_before4 / (2 * m_before4.head<3>().norm());
    auto dir1 = m_after4 / (2 * m_after4.head<3>().norm());
    return (dir0 + dir1).head<3>().normalized();
  }
  Scalar depositedEnergy() const { return m_before4[3] - m_after4[3]; }

 private:
  Acts::GeometryID m_geometryId;
  Barcode m_particleId;
  int32_t m_index = -1;
  Vector4 m_pos4 = Vector4::Zero();
  Vector4 m_before4 = Vector4::Zero();
  Vector4 m_after4 = Vector4::Zero();
};

}  // namespace ActsFatras