ActsFatras/Selectors/KinematicCasts.hpp

0001 // This file is part of the ACTS project.
0002 //
0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
0008
0009 #pragma once
0010
0011 #include "Acts/Utilities/VectorHelpers.hpp"
0012 #include "ActsFatras/EventData/Particle.hpp"
0013
0014 #include <cmath>
0015
0016 namespace ActsFatras::Casts {
0017
0018 /// Retrieve the transverse absolute distance of the position to the origin.
0019 struct Vrho {
0020   /// @brief Extract transverse distance from origin
0021   /// @param particle The particle to extract from
0022   /// @return Transverse distance rho = sqrt(x² + y²) from particle position
0023   double operator()(const Particle& particle) const {
0024     return std::hypot(particle.position().x(), particle.position().y());
0025   }
0026 };
0027
0028 /// Retrieve the longitudinal distance of the position to the origin.
0029 struct Vz {
0030   /// @brief Extract longitudinal distance from origin
0031   /// @param particle The particle to extract from
0032   /// @return Z-coordinate of particle position
0033   double operator()(const Particle& particle) const {
0034     return particle.position().z();
0035   }
0036 };
0037
0038 /// Retrieve the longitudinal absolute distance of the position to the origin.
0039 struct AbsVz {
0040   /// @brief Extract absolute longitudinal distance from origin
0041   /// @param particle The particle to extract from
0042   /// @return Absolute value of Z-coordinate of particle position
0043   double operator()(const Particle& particle) const {
0044     return std::abs(particle.position().z());
0045   }
0046 };
0047
0048 /// Retrieve the direction pseudo-rapidity.
0049 struct Eta {
0050   /// @brief Extract direction pseudo-rapidity
0051   /// @param particle The particle to extract from
0052   /// @return Pseudo-rapidity η = atanh(p_z/p) from particle direction
0053   double operator()(const Particle& particle) const {
0054     // particle direction is always normalized, i.e. dz = pz / p
0055     return std::atanh(particle.direction().z());
0056   }
0057 };
0058
0059 /// Retrieve the direction absolute pseudo-rapidity.
0060 struct AbsEta {
0061   /// @brief Extract absolute direction pseudo-rapidity
0062   /// @param particle The particle to extract from
0063   /// @return Absolute pseudo-rapidity |η| = atanh(|p_z|/p) from particle direction
0064   double operator()(const Particle& particle) const {
0065     // particle direction is always normalized, i.e. dz = pz / p
0066     return std::atanh(std::abs(particle.direction().z()));
0067   }
0068 };
0069
0070 /// Retrieve the transverse momentum.
0071 struct Pt {
0072   /// @brief Extract transverse momentum
0073   /// @param particle The particle to extract from
0074   /// @return Transverse momentum p_T = p × sin(θ) from particle momentum
0075   double operator()(const Particle& particle) const {
0076     // particle direction is always normalized, i.e. dt²+dz²=1 w/ dt²=dx²+dy²
0077     return particle.absoluteMomentum() *
0078            Acts::VectorHelpers::perp(particle.direction());
0079   }
0080 };
0081
0082 /// Retrieve the absolute momentum.
0083 struct P {
0084   /// @brief Extract absolute momentum magnitude
0085   /// @param particle The particle to extract from
0086   /// @return Total momentum magnitude |p| of the particle
0087   double operator()(const Particle& particle) const {
0088     return particle.absoluteMomentum();
0089   }
0090 };
0091
0092 /// Retrieve the total energy.
0093 struct E {
0094   /// @brief Extract total energy
0095   /// @param particle The particle to extract from
0096   /// @return Total energy E = sqrt(p²c² + m²c⁴) of the particle
0097   double operator()(const Particle& particle) const {
0098     return particle.energy();
0099   }
0100 };
0101
0102 }  // namespace ActsFatras::Casts