The definitions of equanimity and disassociation sound really similar, but they are very different things. In Equanimity, you feel a connection to everything, with the sense of self and ego diminished or completely removed. In Disassociation, you feel disconnected from everything, floating free and completely alone. To be honest, I've never experienced equanimity, so I'm going off the descriptions I've read and had explained to me, in my own attempts at mindfulness meditation. Disassociation, I've experienced multiple times. It tends to happen when one is in an extremely stressful emotional state, and it's a big relief when it happens in that context, but it's a self-defense strategy, and not a healthy state. I suspect you could achieve it accidentally when trying for equanimity, but it isn't equanimity.
