Apparently
from Wikipedia
Many Happy Returns is a greeting, usually reserved for birthdays.
The term itself refers to the passing year. Since the 18th century this has been used as a salutation to offer the hope that a happy day being marked would recur many more times. It is now primarily...
As far as I was aware, today was not colliding particles together, it was just the first time the beam has gone round the whole length of the tunnel. On the 21st October the beams will be sent round in opposite directions smashing them together creating black holes!