Three Body Kinematics
e is the virtual photon polarization
x_B is the Bjorken variable
q_qx is the angle between q and x, etc.
negative q in other formulations
corresponds to f=180 deg here
q = p2 + px
mp=938.783 MeV
mn=939.565 MeV
md=1876.124 MeV
m(3H)=2809.432 MeV
m(3He)=2809.413 MeV
m(4He)= 3728.40 MeV

Enter Initial Conditions
m_a   m_b   p_0
final state masses
m_1 m_2 m_x
particle 1 parameters
p_1   th_1   phi_1
particle 2 angles
th_2 phi_2
p_2 q th_q phi_q
e_x p_x th_x phi_x
w Q2 e x_B
th_qx   th_q2 th_2x