How can you detect the particles that you want to find in the Large Hadron Collider? Could there be particles there

Question: How can you detect the particles that you want to find in the Large Hadron Collider? Could there be particles there which you haven't discovered but you are missing?
- Keywords:
  lhc,
  particle,
  research
Asked by animalneuro to Deepak on 14 Mar 2014.
- Deepak Kar answered on 14 Mar 2014:
  
  Very good question!
  
  As we say, looking for a new particle among all the particles that come out of the collision is like trying to find a needle in a haystack. In fact it is worse, since at the LHC, we dont even find the new particles intact, they break up into the other particles which we measure in our detector. Then from their energy and direction, we have the guess if a new particle produced them! So it is more finding pieces of a broken needle in the haystack 😉
  
  Many times, our theorists friends tell what particle they think should exist according to their calculation (like the Higgs, which was predicted 50 years back), and we look for it. Other times, we may want to see if there is particle in a certain mass range. Sometimes, we are looking blindly for anything new!

Question: How can you detect the particles that you want to find in the Large Hadron Collider? Could there be particles there which you haven't discovered but you are missing?