A report by Cornelia Borrmann The preparations are almost complete: the largest particle accelerator in the world, the Large Hadron Collider or LHC, is due to be reactivated after a year of repairs. CERN calls the LHC the largest experiment in the world, with 10,000 scientists from a host of countries working to make it possible.The heart of the machine is a 27 kilometer long ring of magnets that will smash protons together with such force that new sub-atomic particles can be created. Scientist are hoping the three billion euro endeavor will help shed light on some of the most puzzling questions of modern physics.   The particles cycle around the ring in less than one-ten-thousandth of a second, in opposite directions though two parallel pipes until they’ve reached velocities close to the speed of light. When the scientists let the particle beams collide, they produce a tiny but extremely hot fireball in which new particles are created. And to keep the particles on track, all the magnets must maintain the same magnetic field. Otherwise the particles would crash into the walls - and destroy the machine. The less than one-millimeter wide has as much energy as a high speed train. Another challenge is that the superconducting magnets have to be kept extremely cold. Achieving that requires about a hundred tons of liquid helium. Never before have such huge quantities of this dangerous fluid been used at once. It's a daunting enterprise. The scientists have to monitor 17 hundred electrical circuits to keep their supermachine running. And soon the real work is supposed to begin: the hunt for the Higgs Boson. Its existence is based on a highly mathematical theory devised by Peter Higgs and other physicists. To explain, all atoms have a nucleus. And that, in turn, is composed of building blocks. One of those building blocks is called a proton. It contains three particles called quarks.Together, they ought to weigh as much as the proton they constitut...