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Units.hpp
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1 // This file is part of the Acts project.
2 //
3 // Copyright (C) 2016-2019 CERN for the benefit of the Acts project
4 //
5 // This Source Code Form is subject to the terms of the Mozilla Public
6 // License, v. 2.0. If a copy of the MPL was not distributed with this
7 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 
9 #pragma once
10 
11 namespace Acts {
12 
86 
87 namespace UnitConstants {
88 // Length, native unit mm
89 constexpr double fm = 1e-12;
90 constexpr double pm = 1e-9;
91 constexpr double um = 1e-3;
92 constexpr double nm = 1e-6;
93 constexpr double mm = 1.0;
94 constexpr double cm = 10.0;
95 constexpr double m = 1e3;
96 constexpr double km = 1e6;
97 // Shortcuts for commonly used area and volume units. This intentionally
98 // contains not all possible combinations to avoid cluttering the namespace.
99 // Missing area or volume units can always be defined on the fly using the
100 // existing length units e.g. 1fm³ -> 1fm * 1fm * 1fm
101 // Area, native unit mm²
102 constexpr double mm2 = mm * mm;
103 constexpr double cm2 = cm * cm;
104 constexpr double m2 = m * m;
105 // Volume, native unit mm³
106 constexpr double mm3 = mm * mm * mm;
107 constexpr double cm3 = cm * cm * cm;
108 constexpr double m3 = m * m * m;
109 // Time, native unit mm = [speed-of-light * time] = mm/s * s
110 constexpr double s = 299792458000.0;
111 constexpr double fs = 1e-15 * s;
112 constexpr double ps = 1e-12 * s;
113 constexpr double ns = 1e-9 * s;
114 constexpr double us = 1e-6 * s;
115 constexpr double ms = 1e-3 * s;
116 constexpr double min = 60.0 * s;
117 constexpr double h = 3600.0 * s;
118 // Angles, native unit radian
119 constexpr double mrad = 1e-3;
120 constexpr double rad = 1.0;
121 constexpr double degree = 0.017453292519943295; // pi / 180
122 // Energy/mass/momentum, native unit GeV
123 constexpr double eV = 1e-9;
124 constexpr double keV = 1e-6;
125 constexpr double MeV = 1e-3;
126 constexpr double GeV = 1.0;
127 constexpr double TeV = 1e3;
128 // atomic mass unit u
129 constexpr double u = 0.93149410242;
130 // 1eV/c² == 1.782662e-36kg
131 // 1GeV/c² == 1.782662e-27kg
132 // -> 1kg == (1/1.782662e-27)GeV/c²
133 // -> 1g == (1/(1e3*1.782662e-27))GeV/c²
134 constexpr double g = 1.0 / 1.782662e-24;
135 constexpr double kg = 1.0 / 1.782662e-27;
136 // Charge, native unit e (elementary charge)
137 constexpr double e = 1.0;
138 constexpr double C = 1.602176634e19;
139 // Magnetic field, native unit GeV/(e*mm)
140 constexpr double T = 0.000299792458; // equivalent to c in appropriate SI units
141 constexpr double Gauss = 1e-4 * T;
142 constexpr double kGauss = 1e-1 * T;
143 // Amount of substance, native unit mol
144 constexpr double mol = 1.0;
145 } // namespace UnitConstants
146 
147 namespace UnitLiterals {
148 // define user literal functions for the given unit constant
149 #define ACTS_DEFINE_UNIT_LITERAL(name) \
150  constexpr double operator"" _##name(long double x) { \
151  return ::Acts::UnitConstants::name * x; \
152  } \
153  constexpr double operator"" _##name(unsigned long long x) { \
154  return ::Acts::UnitConstants::name * x; \
155  }
156 ACTS_DEFINE_UNIT_LITERAL(fm)
157 ACTS_DEFINE_UNIT_LITERAL(pm)
158 ACTS_DEFINE_UNIT_LITERAL(nm)
159 ACTS_DEFINE_UNIT_LITERAL(um)
160 ACTS_DEFINE_UNIT_LITERAL(mm)
161 ACTS_DEFINE_UNIT_LITERAL(cm)
162 ACTS_DEFINE_UNIT_LITERAL(m)
163 ACTS_DEFINE_UNIT_LITERAL(km)
164 ACTS_DEFINE_UNIT_LITERAL(mm2)
165 ACTS_DEFINE_UNIT_LITERAL(cm2)
166 ACTS_DEFINE_UNIT_LITERAL(m2)
167 ACTS_DEFINE_UNIT_LITERAL(mm3)
168 ACTS_DEFINE_UNIT_LITERAL(cm3)
169 ACTS_DEFINE_UNIT_LITERAL(m3)
170 ACTS_DEFINE_UNIT_LITERAL(fs)
171 ACTS_DEFINE_UNIT_LITERAL(ps)
172 ACTS_DEFINE_UNIT_LITERAL(ns)
173 ACTS_DEFINE_UNIT_LITERAL(us)
174 ACTS_DEFINE_UNIT_LITERAL(ms)
175 ACTS_DEFINE_UNIT_LITERAL(s)
176 ACTS_DEFINE_UNIT_LITERAL(min)
177 ACTS_DEFINE_UNIT_LITERAL(h)
178 ACTS_DEFINE_UNIT_LITERAL(mrad)
179 ACTS_DEFINE_UNIT_LITERAL(rad)
180 ACTS_DEFINE_UNIT_LITERAL(degree)
181 ACTS_DEFINE_UNIT_LITERAL(eV)
182 ACTS_DEFINE_UNIT_LITERAL(keV)
183 ACTS_DEFINE_UNIT_LITERAL(MeV)
184 ACTS_DEFINE_UNIT_LITERAL(GeV)
185 ACTS_DEFINE_UNIT_LITERAL(TeV)
186 ACTS_DEFINE_UNIT_LITERAL(u)
187 ACTS_DEFINE_UNIT_LITERAL(g)
188 ACTS_DEFINE_UNIT_LITERAL(kg)
189 ACTS_DEFINE_UNIT_LITERAL(e)
190 ACTS_DEFINE_UNIT_LITERAL(C)
191 ACTS_DEFINE_UNIT_LITERAL(T)
192 ACTS_DEFINE_UNIT_LITERAL(Gauss)
193 ACTS_DEFINE_UNIT_LITERAL(kGauss)
194 ACTS_DEFINE_UNIT_LITERAL(mol)
195 // not needed anymore. undef to prevent littering the namespace
196 #undef ACTS_DEFINE_UNIT_LITERAL
197 } // namespace UnitLiterals
198 } // namespace Acts