You can pick a little area of bark from one of the branches with your fingernail. If the wood underneath shows a hint of green your tree is still alive. If it is dry and brown then the tree is dead, or at least - that part of it is!
How Can I Tell If My Japanese Maple Tree Is Dead?
It's May and my new Japanese maple tree leaves are wilting. I water regularly but am afraid it's diseased. Does this tree shed it's leaves this time of year?
Check its pulse!