Wikipedia explains colliders this way.
A collider is a type of a particle accelerator involving directed beams of particles. Colliders may either be ring accelerators or linear accelerators.
In particle physics one gains knowledge about elementary particles by accelerating particles to very high kinetic energy and letting them impact on other particles. For sufficiently high energy, a reaction happens that transforms the particles into other particles. Detecting these products gives insight into the physics involved.
To do such experiments there are two possible setups:
  • Fixed target setup: A beam of particles (the projectiles) is accelerated with a particle accelerator, and as collision partner, one puts a stationary target into the path of the beam.
  • Collider: Two beams of particles are accelerated and the beams are directed against each other, so that the particles collide while flying in opposite directions. This process can be used to make strange and anti-matter.
The collider setup is harder to construct but has the great advantage that according to special relativity the energy of an inelastic collision between two particles approaching each other with a given velocity is not just 4 times as high as in the case of one particle resting (as it would be in non-relativistic physics); it can be orders of magnitude higher if the collision velocity is near the speed of light.
For years scientists have used "colliders" to smash together particles traveling at high velocities so the scientists could observe the energies and particles that were released by the collisions. The largest collider to date is the one built in Europe that began operation in 2010. This collider is known as the LHC. Scientists hope that collider will give evidence of a particle called the Higgs boson. That particle (nicknamed by the media the "God particle") was hypothesized by scientists, because it would resolve problems in the Standard Model of particle physics. Many scientists believe that after the Big Bang, space was filled with particles having no mass and traveling at the speed of light. They hypothesized that space is filled with a field called the Higgs Field (named after the scientist who proposed this hypothesis), and that the movement of the mass-less particles through this field gave the particles mass.

Wikipedia says this about the Higgs boson.
The Higgs boson is a hypothetical massive elementary particle that is predicted to exist by the Standard Model (SM) of particle physics. The Higgs boson plays a crucial role in the Higgs mechanism responsible for breaking the electroweak symmetry of the Standard Model . If shown to exist, it would help explain why other elementary particles have mass. It is the only elementary particle predicted by the Standard Model that has not yet been observed in particle physics experiments. Theories that do not need the Higgs boson also exist and would be considered if the existence of the Higgs boson were ruled out. They are described as Higgsless models.
The Higgs mechanism explains why the W and Z bosons, which mediate weak interactions, are massive whereas the related photon, which mediates electromagnetism, is massless. The Higgs boson is expected to be in a class of particles known as scalar bosons. (Bosons are particles with integer spin, and scalar bosons have spin 0.)
Experiments attempting to find the particle are currently being performed using the Large Hadron Collider (LHC) at CERN, and were performed at Fermilab's Tevatron until its closure in late 2011. Some theories suggest that any mechanism capable of generating the masses of elementary particles must become visible at energies above 1.4 TeV; therefore, the LHC (colliding two 3.5 TeV beams) is expected to be able to provide experimental evidence of the existence or non-existence of the Higgs boson. In December 2011, the two main experiments at the LHC (ATLAS and CMS) reported that the data collected up till then hints that the Higgs may exist with a mass around 125 GeV/c. However, the evidence is not yet conclusive.
Many scientists dislike the nickname "God particle" because it is a misleading term. They are not investigating whether God created the universe or not. They are merely trying to explain, from the viewpoint of science, how the universe was created.

Following are additional reports from scientists about colliders.
At the Moriond Conference today, the ATLAS and CMS collaborations at CERN's Large Hadron Collider (LHC) presented preliminary new results that further elucidate the particle discovered last year. Having analysed two and a half times more data than was available for the discovery announcement in July, they find that the new particle is looking more and more like a Higgs boson, the particle linked to the mechanism that gives mass to elementary particles.
It remains an open question, however, whether this is the Higgs boson of the Standard Model of particle physics, or possibly the lightest of several bosons predicted in some theories that go beyond the Standard Model. Finding the answer to this question will take time.
Scientists' hopes that last summer's triumphant trapping of the particle that shaped the post-Big Bang universe would quickly open the way into exotic new realms of physics like string theory and new dimensions have faded this past week (NewsDaily, March 8, 2013).
On Feb. 14, 2013, at 7:24 am, the shift crew in the CERN Control Centre extracted the beams from the Large Hadron Collider, bringing the machine's first three-year running period to a successful conclusion. The LHC's first run has seen major advances in physics, including the discovery of a new particle that looks increasingly like the long-sought Higgs boson, announced on July 4, 2012. And during the last weeks of the run, the remarkable figure of 100 petabytes of data stored in the CERN mass-storage systems was surpassed. This data volume is roughly equivalent to 700 years of full HD-quality movies.
Physicists at UChicago and elsewhere have chased the elusive Higgs boson for more than two decades. The University produced many of the leaders in theory and experimentation whose ideas and instruments have shaped the long quest for the crucial particle, at the LHC and at Fermilab near Chicago. Without the Higgs, theorists believe, the universe would contain no atoms, no elements, no stars, and no people.
But in the last 18 months, as the LHC has scanned through various energies, the Higgs has not showed itself. And at a conference in Mumbai on August 22, CERN scientists revealed news that set the physics community humming: in the energies so far explored, there’s a 95% probability that the Higgs doesn’t exist. Amir Azcel, writing in a guest blog at Scientific American, explains these numbers, considers the tumult in particle physics that will occur should the Higgs prove no more than theoretical, and asks whether Stephen Hawking has just won his infamous bet against the Higgs:
And science bloggers close to the research center are suggesting it might be clear by mid-December that the boson is a chimera and some other mechanism to explain how matter changed to mass at the birth of the cosmos will have to be sought.
At the 25th International Conference on Neutrino Physics and Astrophysics in Kyoto today (June 8, 2012), CERN Research Director Sergio Bertolucci presented results on the time of flight of neutrinos from CERN to the INFN Gran Sasso Laboratory on behalf of four experiments situated at Gran Sasso. The four, Borexino, ICARUS, LVD and OPERA all measure a neutrino time of flight consistent with the speed of light.
After more than 10 years of gathering and analyzing data produced by the U.S. Department of Energy's Tevatron collider, scientists from the CDF and DZero collaborations have found their strongest indication to date for the long-sought Higgs particle. Squeezing the last bit of information out of 500 trillion collisions produced by the Tevatron for each experiment since March 2001, the final analysis of the data does not settle the question of whether the Higgs particle exists, but gets closer to an answer.
As a result, particles of matter are turned into energy, in accordance with Albert Einstein's famous equation describing the conversion of matter into energy: E=mc2. The energy then propagates through space and the system cools. (Something similar happened in the early evolution of the universe.) Consequently, energy turns back into particles of matter and the process is repeated until particles that can exist in reality as we know it are formed.
Experiments using heavy ions at CERN's Large Hadron Collider (LHC) are advancing understanding of the primordial Universe. The ALICE, ATLAS and CMS collaborations have made new measurements of the kind of matter that probably existed in the first instants of the Universe. They will present their latest results at the 2012 Quark Matter conference, which starts August 13 in Washington DC. The new findings are based mainly on the four-week LHC run with lead ions in 2011, during which the experiments collected 20 times more data than in 2010.

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