Leaving for a new job question?

Hi,

I'm starting a new job next week. I think I made a big mistake about telling my current employer the name of my new company....

I have built several good relationships with people at the job I'm leaving, and have a good reputation overall. However, there are 2 middle managers (including my boss), who have never wanted me to succeed (for their own selfish reasons).

I'm worried now that one of them will contact my new employer and try to discredit me (yes.. I know I sound paranoid), but I don't trust them. I don't know why I told people here where I was going...

If they jeopardize my new position, do I have any legal recourse? Do you think it would hurt me to contact HR here, and discuss my concerns?

Thanks