Units.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2016-2019 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

namespace Acts {



namespace UnitConstants {
// Length, native unit mm
constexpr double mm = 1.0;
constexpr double fm = 1e-12 * mm;
constexpr double pm = 1e-9 * mm;
constexpr double nm = 1e-6 * mm;
constexpr double um = 1e-3 * mm;
constexpr double cm = 1e1 * mm;
constexpr double m = 1e3 * mm;
constexpr double km = 1e6 * mm;
// Shortcuts for commonly used area and volume units. This intentionally
// contains not all possible combinations to avoid cluttering the namespace.
// Missing area or volume units can always be defined on the fly using the
// existing length units e.g. 1fm³ -> 1fm * 1fm * 1fm
// Area, native unit mm²
constexpr double mm2 = mm * mm;
constexpr double cm2 = cm * cm;
constexpr double m2 = m * m;
// Volume, native unit mm³
constexpr double mm3 = mm * mm * mm;
constexpr double cm3 = cm * cm * cm;
constexpr double m3 = m * m * m;
// Time, native unit mm = [speed-of-light * time] = mm/s * s
constexpr double s = 299792458000.0;  // = 299792458.0 * (m / 1.0) * 1.0;
constexpr double fs = 1e-15 * s;
constexpr double ps = 1e-12 * s;
constexpr double ns = 1e-9 * s;
constexpr double us = 1e-6 * s;
constexpr double ms = 1e-3 * s;
constexpr double min = 60.0 * s;
constexpr double h = 3600.0 * s;
// Angles, native unit radian
constexpr double mrad = 1e-3;
constexpr double rad = 1.0;
constexpr double degree = 0.017453292519943295;  // = M_PI / 180.0 * rad;
// Energy/mass/momentum, native unit GeV
constexpr double GeV = 1.0;
constexpr double eV = 1e-9 * GeV;
constexpr double keV = 1e-6 * GeV;
constexpr double MeV = 1e-3 * GeV;
constexpr double TeV = 1e3 * GeV;
constexpr double J = 6241509074.460763 * GeV;
constexpr double u = 0.93149410242;
//     1eV/c² == 1.782662e-36kg
//    1GeV/c² == 1.782662e-27kg
// ->     1kg == (1/1.782662e-27)GeV/c²
// ->      1g == (1/(1e3*1.782662e-27))GeV/c²
constexpr double g = 1.0 / 1.782662e-24;
constexpr double kg = 1.0 / 1.782662e-27;
constexpr double e = 1.0;
constexpr double T = 0.000299792458;  // = eV * s / (e * m2);
constexpr double Gauss = 1e-4 * T;
constexpr double kGauss = 1e-1 * T;
constexpr double mol = 1.0;
}  // namespace UnitConstants

namespace UnitLiterals {
// define user literal functions for the given unit constant
#define ACTS_DEFINE_UNIT_LITERAL(name)                        \
  constexpr double operator"" _##name(long double x) {        \
    return ::Acts::UnitConstants::name * x;                   \
  }                                                           \
  constexpr double operator"" _##name(unsigned long long x) { \
    return ::Acts::UnitConstants::name * x;                   \
  }
ACTS_DEFINE_UNIT_LITERAL(fm)
ACTS_DEFINE_UNIT_LITERAL(pm)
ACTS_DEFINE_UNIT_LITERAL(nm)
ACTS_DEFINE_UNIT_LITERAL(um)
ACTS_DEFINE_UNIT_LITERAL(mm)
ACTS_DEFINE_UNIT_LITERAL(cm)
ACTS_DEFINE_UNIT_LITERAL(m)
ACTS_DEFINE_UNIT_LITERAL(km)
ACTS_DEFINE_UNIT_LITERAL(mm2)
ACTS_DEFINE_UNIT_LITERAL(cm2)
ACTS_DEFINE_UNIT_LITERAL(m2)
ACTS_DEFINE_UNIT_LITERAL(mm3)
ACTS_DEFINE_UNIT_LITERAL(cm3)
ACTS_DEFINE_UNIT_LITERAL(m3)
ACTS_DEFINE_UNIT_LITERAL(fs)
ACTS_DEFINE_UNIT_LITERAL(ps)
ACTS_DEFINE_UNIT_LITERAL(ns)
ACTS_DEFINE_UNIT_LITERAL(us)
ACTS_DEFINE_UNIT_LITERAL(ms)
ACTS_DEFINE_UNIT_LITERAL(s)
ACTS_DEFINE_UNIT_LITERAL(min)
ACTS_DEFINE_UNIT_LITERAL(h)
ACTS_DEFINE_UNIT_LITERAL(mrad)
ACTS_DEFINE_UNIT_LITERAL(rad)
ACTS_DEFINE_UNIT_LITERAL(degree)
ACTS_DEFINE_UNIT_LITERAL(eV)
ACTS_DEFINE_UNIT_LITERAL(keV)
ACTS_DEFINE_UNIT_LITERAL(MeV)
ACTS_DEFINE_UNIT_LITERAL(GeV)
ACTS_DEFINE_UNIT_LITERAL(TeV)
ACTS_DEFINE_UNIT_LITERAL(J)
ACTS_DEFINE_UNIT_LITERAL(u)
ACTS_DEFINE_UNIT_LITERAL(g)
ACTS_DEFINE_UNIT_LITERAL(kg)
ACTS_DEFINE_UNIT_LITERAL(e)
ACTS_DEFINE_UNIT_LITERAL(T)
ACTS_DEFINE_UNIT_LITERAL(Gauss)
ACTS_DEFINE_UNIT_LITERAL(kGauss)
ACTS_DEFINE_UNIT_LITERAL(mol)
// not needed anymore. undef to prevent littering the namespace
#undef ACTS_DEFINE_UNIT_LITERAL
}  // namespace UnitLiterals

namespace PhysicalConstants {
// Speed of light
constexpr double c = 1.0;
constexpr double hbar =
    6.582119569509066e-25 * UnitConstants::GeV * UnitConstants::s;
}  // namespace PhysicalConstants

}  // namespace Acts