There is little you can do to deture a starving hawk. First you must make sure that your weak spot in your pen is fixed and check for any other weak spots. If there is a weak spot now that they've found a food source, they'll use it! The only known ways to prevent this further come in two ways; put up reflective surfaces around your coop and your backyard (if the hawk isn't starving, then he will pull out of an attack as he sees his reflection and thinks it's another hawk) or you need to stay with your chickens every time they go outside (though a hawk may still try). Both of these aren't garanteed solutions, the only ones that are, are as fallows:
1. Fix any opening that predators can get into your coop
2. Cover your chicken walk area and pen from above so that patrolling hawks can't easily spot that there is food there
3. If a hawk does attack, keep the birds inside the pen for at least a week so that the hawk doesn't see your backyard as more of a food source
I hope this helped! And please don't shoot, trap or kill Hawks in any way, this is illegal and unfaire economically. Almost 80% of all Hawks die in the first year because they can't hunt or fly with enough skill. Likewise, you may want to put food outside for any animals, don't do that, if Hawks find it, your backyard is now on the feeding list!