I assume you are about the LHC (Large Hadron Collider) that has been completed in 2008.In that case, the answer is zondre doubt: the Higgs boson.
In 1964, this particle was predicted on paper by, among others, Peter Higgs.The particle had never been observed, but a result of the mathematics behind the so-called Standard Model. This model tries in one theory to describe all elementary particles (such as electrons, protons and neutrons), as well as the fundamental forces in between (electromagnetism and the strong and weak nuclear force). The particles we already know impose a lot of restrictions on the mathematical model. Physicists are always looking for the most elegant way to describe this, but sometimes there is something out of the theory that we have not yet found.In the most “simple” model we currently have is that the Higgs particle. It is very heavy and therefore also very unstable. With the energies we are dealing with in everyday life, we would never be able to perceive it directly, but because of the interactions that other particles have with the Higgs field we could declare that elementary particles have the mass that we indeed Measure. If the Higgs boson would not exist, we have to go to much more complex theories, and that goes against the hopes and beliefs of many scientists that the simplest and most elegant solution is often the correct one.
One problem is that the standard model is in some way an empirical model: there are a lot of parameters in which we can ‘ rotate ‘ to change the model so that it describes the reality (and so for example the right masses and interactions Hatch).We therefore knew at most about what energy range we could find the Higgs particle, if it exists.
One of the main goals of the LHC was to find the Higgs particle -not directly, but because specific interactions leave a certain trace of particles from which it can be traced that a Higgs boson should be involved, and from the Energies and pathways of the purest particles and the residual particles the mass of the Higgs boson could be derived.
In 2008, the LHC was first put into use, but quite soon an accident happened which caused it to freeze again for a year.Over the period 2010-2013 the energy is slowly increased. At the end of 2012, one of the two detectors observed the decay response that one was looking for, demonstrating with very large statistical probability that the Higgs boson exists and thus gives strong support to the ‘ elegant ‘ version of the Standard Model above all variants without or correctly with multiple Higgs fields.
Following the discovery, Fran莽ois Englert and Peter Higgs were awarded the Nobel Prize in 2013 for their work from about 30 to 40 years earlier.
In the LHC, experiments on high energy are still being carried out, and an even larger accelerator (the Very Large Hadron Collider) is already being discussed, but the discovery of the Higgs boson was one of the main goals and in terms of the Particle physics is one of the biggest and most important discoveries of recent years.