MisalignmentUtils.h

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// Copyright 2019-2026 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.
 
#ifndef O2_ITS3_ALIGNMENT_MISALIGNMENTUTILS_H
#define O2_ITS3_ALIGNMENT_MISALIGNMENTUTILS_H
 
#include <array>
#include <cstddef>
#include <map>
#include <string>
#include <utility>
 
#include "ITS3Align/AlignmentMath.h"
#include "MathUtils/LegendrePols.h"
 
namespace o2::its3::align
{
 
// Legendre parameterisation of the open half-shell deformation, matching InextensionalDOFSet: inextensional
// coefficients f_k, g_k of the normalised azimuth u, plus optional strictly radial modes h_{k,l} (l >= 1) in P_k(u)
// P_l(v). See AlignmentDOF.h for the displacement field.
struct InextensionalMisalignment {
  std::map<int, double> f;                 // k -> f_k
  std::map<int, double> g;                 // k -> g_k
  std::map<std::pair<int, int>, double> h; // (k, l) -> h_{k,l}, l >= 1
};
 
struct SensorMisalignment {
  o2::math_utils::Legendre2DPolynominal legendre;
  bool hasLegendre{false};
  InextensionalMisalignment inextensional;
  bool hasInextensional{false};
 
  bool empty() const noexcept { return !hasLegendre && !hasInextensional; }
};
 
struct MisalignmentModel {
  static constexpr std::size_t NSensors = 6;
  std::array<SensorMisalignment, NSensors> sensors{};
 
  bool empty() const noexcept;
  const SensorMisalignment& operator[](std::size_t idx) const { return sensors[idx]; }
  SensorMisalignment& operator[](std::size_t idx) { return sensors[idx]; }
};
 
struct MisalignmentFrame {
  int sensorID{-1};
  int layerID{-1};
  double x{0.};     // tracking-frame X / nominal radius at the measurement
  double alpha{0.}; // tracking-frame alpha
  double z{0.};     // tracking-frame measurement z
};
 
struct MisalignmentShift {
  double dy{0.};
  double dz{0.};
  bool accepted{true};
 
  MisalignmentShift& operator+=(const MisalignmentShift& other)
  {
    dy += other.dy;
    dz += other.dz;
    accepted = accepted && other.accepted;
    return *this;
  }
};
 
MisalignmentModel loadMisalignmentModel(const std::string& jsonPath);
MisalignmentShift evaluateLegendreShift(const SensorMisalignment& sensor, const MisalignmentFrame& frame, const TrackSlopes& slopes);
MisalignmentShift evaluateInextensionalShift(const SensorMisalignment& sensor, const MisalignmentFrame& frame, const TrackSlopes& slopes);
 
} // namespace o2::its3::align
 
#endif