Physics/Scattering/Highland.hpp

0001 // This file is part of the Acts project.
0002 //
0003 // Copyright (C) 2018 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 http://mozilla.org/MPL/2.0/.
0008
0009 #pragma once
0010
0011 #include "Acts/Material/Interactions.hpp"
0012 #include "Fatras/Kernel/detail/RandomNumberDistributions.hpp"
0013
0014 namespace Fatras {
0015
0016 /// @The struct for the Highland-based scattering
0017 ///
0018 /// This will scatter particles with a single gaussian distribution
0019 /// according to the highland formula.
0020 struct Highland {
0021
0022   /// @brief Call operator to perform this scattering
0023   ///
0024   /// @tparam generator_t is a random number generator type
0025   /// @tparam detector_t is the detector information type
0026   /// @tparam particle_t is the particle information type
0027   ///
0028   /// @param[in] generator is the random number generator
0029   /// @param[in] detector the detector information
0030   /// @param[in] particle the particle which is being scattered
0031   ///
0032   /// @return a scattering angle in 3D
0033   template <typename generator_t, typename detector_t, typename particle_t>
0034   double operator()(generator_t &generator, const detector_t &detector,
0035                     particle_t &particle) const {
0036
0037     // Gauss distribution, will be sampled sampled with generator
0038     GaussDist gaussDist = GaussDist(0., 1.);
0039
0040     double qop = particle.q() / particle.p();
0041     double theta0 = Acts::computeMultipleScatteringTheta0(
0042         detector, particle.pdg(), particle.m(), qop, particle.q());
0043     // Return projection factor times sigma times grauss random
0044     return M_SQRT2 * theta0 * gaussDist(generator);
0045   }
0046 };
0047
0048 } // namespace Fatras