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The first attempt to circulate a beam in the Large Hadron Collider (LHC) will be made on 10 September. This news comes as the cool down phase of commissioning CERN’s new particle accelerator reaches a successful conclusion.
Physicists around the world, some in pajamas and others with champagne, celebrated the first tests on Wednesday of a huge particle-smashing machine they hope will simulate the "Big Bang" that created the universe.
Age of the Universe
Astronomical observations indicate that the universe is 13.73 ± 0.12 billion years old and at least 93 billion light years across. The event that started the universe is called the Big Bang. At this point in time all matter and energy of the observable universe was concentrated in one point of infinite density. After the Big Bang, the universe started to expand to its present form. Since special relativity states that matter cannot exceed the speed of light, in a fixed space-time, it may seem paradoxical that two galaxies can be separated by 93 billion light years in 13 billion years; however, this separation is a natural consequence of general relativity.
Big Bang
The Big Bang is the cosmological model of the universe that is best supported by all lines of scientific evidence and observation. The essential idea is that the universe has expanded from a primordial hot and dense initial condition at some finite time in the past and continues to expand to this day.
After Edwin Hubble discovered in 1929 that the distances to far away galaxies were generally proportional to their redshifts, this observation was taken to indicate that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point. The farther away, the higher the apparent velocity. If the distance between galaxy clusters is increasing today, everything must have been closer together in the past. This idea has been considered in detail back in time to extreme densities and temperatures, and large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of the theory. But these accelerators can only probe so far into such high energy regimes. Without any evidence associated with the earliest instant of the expansion, the Big Bang theory cannot and does not provide any explanation for such an initial condition, rather explaining the general evolution of the universe since that instant. The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the universe, as logically and quantitatively detailed according to Big Bang nucleosynthesis.
Large Hadron Collider
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator complex, intended to collide opposing beams of protons charged with very high energy. Its main purpose is to explore the validity and limitations of the Standard Model, the current theoretical picture for particle physics. It is theorized that the collider will confirm the existence of the Higgs boson, the observation of which could confirm the predictions and missing links in the Standard Model, and could explain how other elementary particles acquire properties such as mass.
The LHC was built by the European Organization for Nuclear Research (CERN), and lies underneath the Franco-Swiss border near Geneva, Switzerland. It is funded by and built in collaboration with over eight thousand physicists from over eighty-five countries as well as hundreds of universities and laboratories. The LHC is already operational and is presently in the process of being prepared for collisions. The first beams were circulated through the collider on 10 September 2008, and the first high-energy collisions are planned to take place after the LHC is officially unveiled on 21 October.
Although a few individuals have questioned the safety of the planned experiments in the media and through the courts, the consensus in the scientific community is that there is no conceivable threat from the LHC particle collisions.
Higgs boson
The Higgs boson or BEH Mechanism, popularised as the "God Particle", is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics; and is the only Standard Model particle not yet observed. An experimental observation of it would help to explain how otherwise massless elementary particles cause matter to have mass. More specifically, the Higgs boson would explain the difference between the massless photon and the relatively massive W and Z bosons. Elementary particle masses, and the differences between electromagnetism (caused by the photon) and the weak force (caused by the W and Z bosons), are critical to many aspects of the structure of microscopic (and hence macroscopic) matter; thus, if it exists, the Higgs boson is an integral and pervasive component of the material world.
No experiment has yet directly detected the existence of the Higgs boson, but this may change as the recently finished Large Hadron Collider (LHC) at CERN begins to produce new scientific data. The Higgs mechanism, which gives mass to vector bosons, was theorized in August 1964 by François Englert and Robert Brout in October of the same year by Peter Higgs, working from the ideas of Philip Anderson, and independently by G. S. Guralnik, C. R. Hagen, and T. W. B. Kibble who worked out the results by the spring of 1963.
Higgs proposed that the existence of a massive scalar particle could be a test of the theory, a remark added to his Physical Review letter at the suggestion of the referee. Steven Weinberg and Abdus Salam were the first to apply the Higgs mechanism to the electroweak symmetry breaking. The electroweak theory predicts a neutral particle whose mass is not far from that of the W and Z bosons.
Purpose of the Experiment
The existence of the Higgs boson would be a significant step in the search for a Grand Unified Theory, which seeks to unify three of the four known fundamental forces: electromagnetism, the strong nuclear force and the weak nuclear force, leaving out only gravity. The Higgs boson may also help to explain why gravitation is so weak compared with the other three forces.
Higgs boson may be produced at the LHC. Here, two gluons decay into a top/anti-top pair which then combine to make a neutral Higgs (H0).
When in operation, about seven thousand scientists from eighty countries will have access to the LHC. Physicists hope to use the collider to answer the following questions:
* Is the popular Higgs mechanism for generating elementary particle masses in the Standard Model realised in nature? If so, how many Higgs bosons are there, and what are their masses?
* Will the more precise measurements of the masses of the quarks continue to be mutually consistent within the Standard Model?
* Do particles have supersymmetric ("SUSY") partners?
* Why are there apparent violations of the symmetry between matter and antimatter?
* Are there extra dimensions, as predicted by various models inspired by string theory, and can we "see" them?
* What is the nature of dark matter and dark energy?
* Why is gravity so many orders of magnitude weaker than the other three fundamental forces?
Renowned British astrophysicist Stephen Hawking has bet against the mega-experiment finding the elusive Higgs particle. "I think it will be much more exciting if we don't find the Higgs. That will show something is wrong, and we need to think again. I have a bet of $100 that we won't find the Higgs," Hawking speculated, but the experiment could discover superpartners, particles that would be supersymmetric partners to particles already known. "Their existence would be a key confirmation of string theory, and they could make up the mysterious dark matter that holds galaxies together. Whatever the LHC finds, or fails to find, the results will tell us a lot about the structure of the universe," he said.
Test timeline
September 2008
The LHC physics program is mainly based on proton–proton collisions. The first beam was circulated through the collider on the morning of 10 September 2008. CERN successfully fired the protons around the tunnel in stages, 3 km at a time. The particles were fired in a clockwise direction into the accelerator and successfully steered around it at 10:28 am local time. The LHC successfully completed its first major test: after a series of trial runs, two white dots flashed on a computer screen showing the protons traveled the full length of the collider. It took less than one hour to guide the stream of particles around its inaugural circuit. CERN next successfully sent a beam of protons in a counterclockwise direction.
October 2008
The first high-energy collisions are planned to take place after the LHC is officially unveiled on 21 October 2008.
Cost of the Experiment
The total cost of the project is anticipated to be € 3.2–6.4 billion. The construction of LHC was approved in 1995 with a budget of 2.6 billion Swiss francs (€ 1.6 billion), with another 210 million francs (€ 140 million) towards the cost of the experiments. However, cost over-runs, estimated in a major review in 2001 at around 480 million francs (€ 300 million) for the accelerator, and 50 million francs (€ 30 million) for the experiments, along with a reduction in CERN's budget, pushed the completion date from 2005 to April 2007. The superconducting magnets were responsible for 180 million francs (€ 120 million) of the cost increase. There were also engineering difficulties encountered while building the underground cavern for the Compact Muon Solenoid, in part due to faulty parts loaned to CERN by fellow laboratories Argonne National Laboratory and Fermilab.
Operational safety
The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the huge energy stored in the magnets and the beams. While operating, the total energy stored in the magnets is 10 GJ (equivalent to 2.4 tons of TNT) and the total energy carried by the two beams reaches 724 MJ.
Loss of only one ten-millionth part (10−7) of the beam is sufficient to quench a superconducting magnet, while the beam dump must absorb an energy equivalent to that of a typical air-dropped bomb. These immense energies are even more impressive considering how little matter is carrying it: under nominal operating conditions (2,808 bunches per beam, 1.15×10 11 protons per bunch), the beam pipes contain 1.0×10-9 gram of hydrogen, which, in standard conditions for temperature and pressure, would fill the volume of one grain of fine sand.
Superconductivity
Superconductivity was discovered in 1911, a practical superconducting electromagnet had to await the discovery of superconductors that could stand high magnetic fields. The first successful superconducting magnet was built by George Yntema in 1954 using Niobium wire and achieved a field of 0.71 T at 4.2 K. Widespread interest was sparked by Kunzler's 1961 discovery of the advantages of niobium-tin as a high Hc, high current winding material. In 2007 a magnet with windings of YBCO achieved a world record field of 26.8 Tesla.