Disclaimer: this is purposefully obtuse.
Other effects in the game which explicitly state they kill you:
Shadows, succubi, massive damage, death saving throws, beholder death ray (notably not even their disintegration ray kills you), power word kill, vampires, mind flayers, night hags, drow inquisitors.
Clearly, if they intended for disintegration to kill you, they’d have said so. Since specific overrides general, and there is no general rule that disintegrated creatures are dead, I rest my case. QED.
The rules state that you either die or fall unconscious when you have 0 hit points. The definition of “unconscious” in Appendix A specifies that you are incapacitated AND can’t move or speak AND are unaware of your surroundings.
EDIT: Maybe I shouldn’t assume you’re talking about 5e. I have no idea about 5.5e or any other edition