Constants.h

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2013-2021  Laurent Forthomme
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef CepGen_Physics_Constants_h
#define CepGen_Physics_Constants_h
 
#include <cmath>
 
namespace cepgen {
  namespace constants {
    constexpr double ALPHA_EM = 1. / 137.035999;
#if !defined(__CINT__) && !defined(__CLING__)
    constexpr double G_EM_SQ = 4. * M_PI * ALPHA_EM;
#endif
    constexpr double ALPHA_QCD = 0.1184;  // at the Z pole
    constexpr double GEVM2_TO_PB = 0.389351824e9;
    constexpr double GEVM1_TO_M = 0.1973269804e-15;
    constexpr double G_F = 1.1663787e-5;
  }  // namespace constants
}  // namespace cepgen
 
#endif