TrackGenerator.cxx

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
 
 
#include "MIDTestingSimTools/TrackGenerator.h"
 
namespace o2
{
namespace mid
{
 
//______________________________________________________________________________
std::vector<Track> TrackGenerator::generate()
{
  std::poisson_distribution<> distTracks(mMeanTracksPerEvent);
  int nTracks = distTracks(mGenerator);
  return generate(nTracks);
}
 
//______________________________________________________________________________
std::vector<Track> TrackGenerator::generate(int nTracks)
{
  std::vector<Track> tracks;
  Track track;
  std::array<float, 3> pos;
  std::array<float, 2> dir;
  for (int itrack = 0; itrack < nTracks; ++itrack) {
    for (int ipos = 0; ipos < 3; ++ipos) {
      pos[ipos] =
        std::uniform_real_distribution<float>{mPositionLimits[2 * ipos], mPositionLimits[2 * ipos + 1]}(mGenerator);
    }
    track.setPosition(pos[0], pos[1], pos[2]);
 
    std::array<float, 4> limits = getLimitsForAcceptance(pos);
 
    for (int idir = 0; idir < 2; ++idir) {
      dir[idir] = std::uniform_real_distribution<float>{limits[2 * idir], limits[2 * idir + 1]}(mGenerator);
    }
    track.setDirection(dir[0], dir[1], 1.);
    tracks.push_back(track);
  }
  return tracks;
}
 
//______________________________________________________________________________
std::array<float, 4> TrackGenerator::getLimitsForAcceptance(std::array<float, 3> pos)
{
  std::array<float, 4> limits = mSlopeLimits;
  float dZ = -1600. - pos[2];
  if (dZ == 0.) {
    dZ = 0.0001;
  }
 
  // These are the maximum x and y position of MT11 with the standard alignment
  std::array<float, 2> maxValues{{257., 306.7}};
  for (int icoor = 0; icoor < 2; ++icoor) {
    int imin = 2 * icoor;
    int imax = 2 * icoor + 1;
    float minSlope = (pos[icoor] - maxValues[icoor]) / dZ;
    float maxSlope = (maxValues[icoor] - pos[icoor]) / dZ;
    if (minSlope > limits[imin]) {
      limits[imin] = minSlope;
    }
    if (maxSlope < limits[imax]) {
      limits[imax] = maxSlope;
    }
  }
  return limits;
}
} // namespace mid
} // namespace o2