I recently got a baby corn, she's only 11 inches long, and I tried to feed her a head on the fourth day and it didnt work, so around a week after I got her I fed her the head and shoulders of a pinky mouse. She ate it right in front of us! My experience with Kali (my snake) is that if she doesn't immediately show interest in the food item she wont eat it. I suggest feeding it a head or something around the size of the snake's head for the first time, and moving up to a bigger size later.
Did your snake come in a deli cup? What I do is put the food item (slightly warmer than room temp.) in the container that you recieved the snake in and putting the snake in the warm side of the viv. It seems to be the least stressful for the snake.
Jicin might be right too (i just want to say that pet store people know nothing about corn snakes, DONT LISTEN TO THEM! A person at my pet store told me to feed my baby worms!). You could have a problem feeder on your hands. If it doesnt take a mouse for the first few times (and you've brained it and given it a head), you could get Lizard Maker, or rub an anole on a frozen thawed pinky, hatchlings seem to like anoles more than mice.
Also, try doing a search at google.com for "corn snake care sheet" or "problem feeders" and see what comes up. And buy the Corn Snake Manual if you can, I have it and it's great.
This is just my experience, I am by no means an expert. Hope you can get your baby to eat!