Since the balls are in insulating barrels, it has no charge exchange with the earth, so it maintains its initial charge.
When the ball a touches the ball b and since the two are metallic the charge is distributed over the entire surface, by separating the two spheres that are of the same radius, the load was distributed between the two,
q_end = q₀ / 2
q_end = (q / 2) / 2
q_end = q / 4
This is the charge on each ball.
If we keep touching the balls nothing else happens because the charges are already equal in both.
