Games : Can I attack a World Boss, leave the area and still get a reward?

I've noticed that sometime I participate to an event (protect a random NPC, helping kill Centaurs/Ogres, etc.) but not on purpose. By not on purpose I mean that I simply crossed path with this event on my way to somewhere else and barely participate in it (e.g. Just threw an attack). However no matter how far I went from the event's zone I still recieved the Gold/Karma/XP.

Is it the same with World's Boss that leave a chest of loot after death ? Can I simply come > hit the Boss once > leave the area and still come back to a chest of loot ?