- #1

- 89

- 0

I am taking 'field theory' course this semster and I am reading 'quantum field theory' by mandl and shaw.

In chapter 8, equation (8.9) we see:

E_1 E_2 v_rel=〖[(p_1 p_2 )^2-m_1^2 m_2^2]〗^(1/2)

and we know that as p is a four vector:

p=(E,P)=m

so p_1 p_2 = m_1 m_2

!!!

Isn't it strange?!

I think the right hand side of eq(8.9)should be zero then!!!

what am I donig wrong?!