The antenna on my phantom 3 standard has been ripped off by my cat :-(

But the signal cable are left so I am woundering if you can fly fly it without the antenna.

You could probably fly without the antenna. Your range will undoubtedly be shorter.
Your controller is a rf transmitter/receiver, the antennas tuned to the proper frequency. Without the antenna it is no longer tuned and transmitter damage could occur.

I would NOT. Would most likely damage the RC, and could possibly cause a crash.