KinematicCasts.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/Utilities/VectorHelpers.hpp"
#include "ActsFatras/EventData/Particle.hpp"

#include <cmath>

namespace ActsFatras {
namespace Casts {

struct Vrho {
  double operator()(const Particle& particle) const {
    return std::hypot(particle.position().x(), particle.position().y());
  }
};

struct Vz {
  double operator()(const Particle& particle) const {
    return particle.position().z();
  }
};

struct AbsVz {
  double operator()(const Particle& particle) const {
    return std::abs(particle.position().z());
  }
};

struct Eta {
  double operator()(const Particle& particle) const {
    // particle direction is always normalized, i.e. dz = pz / p
    return std::atanh(particle.direction().z());
  }
};

struct AbsEta {
  double operator()(const Particle& particle) const {
    // particle direction is always normalized, i.e. dz = pz / p
    return std::atanh(std::abs(particle.direction().z()));
  }
};

struct Pt {
  double operator()(const Particle& particle) const {
    // particle direction is always normalized, i.e. dt²+dz²=1 w/ dt²=dx²+dy²
    return particle.absoluteMomentum() *
           Acts::VectorHelpers::perp(particle.direction());
  }
};

struct P {
  double operator()(const Particle& particle) const {
    return particle.absoluteMomentum();
  }
};

struct E {
  double operator()(const Particle& particle) const {
    return particle.energy();
  }
};

}  // namespace Casts
}  // namespace ActsFatras