text: /**************************************/
  /*																		*/
  /*  Created by Nick Tyler             */
  /*	University Of South Carolina      */
  /**************************************/
  
  #ifndef CONSTANTS_H_GUARD
  #define CONSTANTS_H_GUARD
  
  #include <unordered_map>
  #include "TMath.h"
  
  static const int MAX_PARTS = 100;
  static const int N_SIGMA = 3;
  static const double PI = TMath::Pi();
  static const float INV_SQRT_2PI = TMath::Sqrt(2 * TMath::Pi());
  static const double D2R = PI / 180.0;
  static const int POSITIVE = 1;
  static const int NEGATIVE = -1;
  static const double E1D_E0 = 4.81726;  // GeV
  
  static const double SOL = 29.9792458;
  // misc. constants
  static const double FSC = 0.00729735253;
  static const double NA = 6.02214129E23;               // Avigadro's number
  static const double QE = 1.60217646E-19;              // Charge or electron
  static const double FS_ALPHA = 0.007297352570866302;  // Fine structure alpha
  
  // particle codes, usually PDG codes, but always those used in BOS
  static const int PROTON = 2212;
  static const int NEUTRON = 2112;
  static const int PIP = 211;
  static const int PIM = -211;
  static const int PI0 = 111;
  static const int KP = 321;
  static const int KM = -321;
  static const int PHOTON = 22;
  static const int ELECTRON = 11;
  
  // PDG particle masses in GeV/c2
  static const double MASS_P = 0.93827203;
  static const double MASS_N = 0.93956556;
  static const double MASS_E = 0.000511;
  static const double MASS_PIP = 0.13957018;
  static const double MASS_PIM = 0.13957018;
  static const double MASS_PI0 = 0.1349766;
  static const double MASS_KP = 0.493677;
  static const double MASS_KM = 0.493677;
  static const double MASS_G = 0.0;
  static const double MASS_OMEGA = 0.78265;
  
  static std::unordered_map<int, double> mass_map = {{PROTON, MASS_P}, {-PROTON, MASS_P},  {NEUTRON, MASS_N},  {PIP, MASS_PIP},
                                     {PIM, MASS_PIM},  {PI0, MASS_PI0},    {KP, MASS_KP},      {KM, MASS_KM},
                                     {PHOTON, MASS_G}, {ELECTRON, MASS_E}, {-ELECTRON, MASS_E}};
  
  #endif
  