You can create a new namespace via tctl, or programmatically, see this post for examples.
Once the namespace is created you can set up you workers that listen to task queues on that new namespace. You should not have to restart your current workers if that is the question.
Namespace is unit of isolation in Temporal, and you can definitely have multiple namespaces setup in your prod environment.
Note that at this time, namespace deletion is not yet supported, follow this issue to track the progress on that.