how to disable reflection on a mesh

hi, i have a silly question here, please help me
i have two meshs here, one is a cube,another is a head sharp mesh, they have the same material(just white color linked to emissive node), i want that when they step over, i shall can’t see the sharp of that head mesh(it should blend into that cube background) but by now i can still see that grey sharp of the head, what should i set up to achieve this?

below is the image,sorry for my english