Have they used the LHC to see if any subparticles fly off a particle before collision? Have they used the LHC to see if a particle gives off any subparticles precollision?
 A: I suppose the question is from an interested student.

Have they used the LHC to see if a particle gives off any subparticles precollision?

What is the LHC? It is a cirular collider, where protons are formed into two opposing beams of very high energy and with manipulation with magnetic fields, the beams made to collide head on. Then instruments are all around the head on collision region to measure the results of the collision.
Protons are stable, they do not decay. The beam of protons going around is made so that protons move parallel to each other in each beam before brought into a collision. Since they are charged and in a magnetic field, they do give off photons, which are the expected synchroton radiation, compensated by the magnets in the tunnel, described in the link, so that they do not lose momentum and come with a fixed known momentum at the collision point of the beams.
If  protons would shed other particles the calculations for the beams would not work, because they are made for synchroton radiation only , so this is an experimental proof that no other then photons are shed before collision.
So the answer is that the successful manipulation of the proton beams shows that only electromagnetic radiation, photons, is shed , which is compensated with calculations to keep the beam momentum fixed.
This answers for the LHC. For other accelerators, the beam could consist of particles that decay, as Kaons, and then a decay could happen , which means that the beam would have one less Kaon, as the decay parts would fly apart out of the beam line.
A: Yes. But it isn't to find out if particles decay all by themselves. Many do. This can be useful.
This video is about DUNE, an experiment at Fermilab. Fermilab is one of the premier subatomic crash test facilities. They study many things, but neutrinos is one of their specialties. The video explains why. What is the DUNE experiment?
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