実験系を計算しました。下記は如何でしょうか？
正しいでしょうか？


s =.;
u =.;
z =.;
t =.;
(*u=-2*k*q+m^2;
t=2 m^2-s-u;
z=1+t/(2 *k3^2);
w=1+u/(2 *k3^2);*)

k0 = (s - m^2)/ Sqrt[s];
k1 = 0;
k2 = 0;
k3 = -(s - m^2)/ Sqrt[s];

p0 = m;
p1 = 0;
p2 = 0;
p3 = 0;

j0 = (s - m^2)/(2 Sqrt[s]);
j1 = -(s - m^2)/(2 Sqrt[s])*Sqrt[1 - w^2];
j2 = 0;
j3 = (s - m^2)/(2 Sqrt[s])*w;

q0 = (s + m^2)/(2 Sqrt[s]);
q1 = (s - m^2)/(2 Sqrt[s])*Sqrt[1 - z^2];
q2 = 0;
q3 = (s - m^2)/(2 Sqrt[s])*z;

Print["(計算確認*)"];

p = p0*p0 - p1*p1 - p2*p2 - p3*p3;
q = q0*q0 - q1*q1 - q2*q2 - q3*q3;
k = k0*k0 - k1*k1 - k2*k2 - k3*k3;
j = j0*j0 - j1*j1 - j2*j2 - j3*j3;

Print["(*０になる*)"];

Simplify[(p + k)^2 - (j + q)^2]
Simplify[(p - q)^2 - (k - j)^2]
Simplify[(p - j)^2 - (q - k)^2]
Simplify[k]
Simplify[j]

Print["(*mになる*)"];
Simplify[p]
Simplify[q]

s = m^2;

Print["(*０になる*)"];
Simplify[p + k - j - q]
Simplify[k3 - (j3 + q3)](*z軸のつり合い*)
Simplify[j1 - q1](*ｙ軸のつり合い*)