- #1

Guaicai

- 8

- 0

## Homework Statement

In a two-particle collision the square of the invariant mass is.

M is total mass of the system (M

^{2}is the square of the total mass)

m is the mass of each particles

E is the energy of each particles

p is momentum vector of eache particles

## Homework Equations

M

^{2}= (E

_{1}+E

_{2})

^{2}- (p

_{1}+p

_{2})

^{2}= m

_{1}

^{2}+m

_{2}

^{2}+2(E

_{1}E

_{2}- p

_{1}⋅ p

_{2})

now know the each energy E = mc

^{2}, here set the c =1 (Speed of Light),

## The Attempt at a Solution

But how the momentum have dot product in this equation ? How the dot product p

_{1}⋅ p

_{2}can derive from (p

_{1}+p

_{2})

^{2}?