seeing my ex today and don't know how to react!

Im going to an event today and im pretty sure he is going to be there with his new girl. He broke up a 3 year relationship a month ago. It was totally out of the blue and unexpected. Later I found out he was with someone else. S

She’s not his type and I know he still thinks about me, but he sure as hell knows how to hide it.

Please I need some tips today for when I see them both together.
I know my heart will be racing and I will become jelous and might cry but I can’t give them the satisfaction.

What can I do?

(1) Keep the interaction as short as you possibly can, without obviously running off.

(2) Be polite-- but distant. “How are you? Good? I’m so glad. Is this Insert Her Name Here? I love your shoes!” (Try to say something nice about something she’s wearing, it saves you the lie of, “It’s nice to meet you.”) “Excuse me, have a good day.” And make your exit. He won’t be expecting to talk long, so keep it as short as you can.

Good luck!