Why do you want to put the Arduino asleep, when you want to control a power LED installation?
Why a touch button, if a mechanical switch will do better what you want?
If it's for learning purposes, let a timer wake up the Arduino every now and then, make it look for a sensor touch, and if not touched put it back asleep. This is how e.g. a remote control or other circuits work, which only wait most of the time for some user action.