PKinematics.h

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// Author: M.A. Kagarlis
// Written: 6.1.00
// PKinematics Class Header
 
#ifndef _PKINEMATICS_H_
#define _PKINEMATICS_H_
 
#include "PStaticData.h"
 
class PKinematics {
  // useful static kinematics functions
 
 public:
  static double lambda(double M, double m1, double m2) {
    // Kaellen function
    double y = (m1+m2);
    if (M<y) return 0.;
    y *= y;
    double x=M*M, z=(m1-m2)*(m1-m2), w=(x-y)*(x-z);
    return (w>0.) ? w : 0.;
  }
 
  static double pcms2(double M, double m1, double m2) {
    // cm momentum^2 for the decay of M to m1 and m2
    return (M>0.) ? 0.25*lambda(M,m1,m2)/(M*M) : 0.;
  }
 
  static double pcms(double M, double m1, double m2) {
    // cm momentum for the decay of M to m1 and m2
      return sqrt(pcms2(M,m1,m2));
  }
 
  static double pcmt(double m, double t) {
    const double mp = makeStaticData()->GetParticleMass("p"),
    mp2 = mp*mp;
    double m2 = m*m;
    double arg = m2+mp2-t;
    arg = 0.25*arg*arg/m2 - mp2;
    return (arg>0.) ? sqrt(arg) : 0. ;
  }
 
  static void rotes(double c, double s, double c2, double s2, double *pr) {
    // rotation used by GENBOD
    double sa = *pr,
    sb = *(pr+1),
    a = sa*c-sb*s;
    *(pr+1) = sa*s+sb*c;
    double b = *(pr+2);
    *pr = a*c2-b*s2;
    *(pr+2) = a*s2+b*c2;
  }
};
 
#endif // _KINEMATICS_H_