Possible Decay of Omega Minus Particle?

[sam_021]

Homework Statement

As you can see this decay is said to be possible

The Attempt at a Solution

but i don't get it because isn't charge conservation violated ?
omega minus --> Q=-1
Xi--> Q=0
negative pion -- > Q=-1/3

 

[I like Serena]

A negative pion has charge -1.
It consists of the quarks down and anti-up.