world’s largest machine termed Large Hadron Collider (LHC) at the European Centre for Nuclear Research (CERN) in Geneva is going to give the scientists a closer look at the makeup of matter and bridging in gaps in knowledge or possibly reshaping theories. On Sept.10, the first beams of protons were fired around the 27-km tunnel to test the controlling strength of the world’s largest superconducting magnets. There will still be about a month before these beams travelling in opposite directions collide with each other to see what’s in the atomic structure. 
The debris from these collisions i.e. showers of subatomic particles will be tracked and recorded by the detectors. These results could radically change the understanding of the physical world. Another most highly expected milestone is detection of the Higgs Boson, sometimes called the god particle, in the standard model of particle physics, or what makes up the atomic structure.
This multibillion-dollar LHC will explore the tiniest particles and bring us closer to re-enacting the big bang, the theory according to which a colossal explosion created the universe. Teams of physicists will analyse the particles created during the collisions by using special detectors employed in a number of experiments dedicated.
It contains a circular tunnel with a circumference of 27 km at a depth ranging from 50 to 175m underground. This 3.8 m diameter, concrete-lined tunnel was constructed between 1983 and 1988 formerly for use to house an electron-positron collider (LEP). Surface buildings hold ancilliary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants. The collider tunnel has two adjacent beam pipes, each for a proton beam (a proton is one type of hadron). The two beams are allowed to travel in opposite directions around the ring and are bent by some 1,232 magnets to keep their path circular.
Another 392 additional focusing magnets are used to keep the beams focused so that beams have maximum chances of colliding at the four intersection points. In total, over 1,600 superconducting magnets each weighing over 27 tonnes are installed.
To keep these magnets at the operating temperature of – 271.1°C (1.9K), about 96 tonnes of liquid helium is needed, which makes LHC the largest cryogenic facility in the world.
The protons can be accelerated from 450 giga electorn-volt (GeV) to 7 tera electron-volt ( TeV) by changing the field of the superconducting bending magnets from 0.54 T to 8.3 T. Each proton will have energy of 7 TeV, thus, totaling the collision energy equal to14 TeV.
The proton will take less than 90 microseconds to travel once around the main ring (at a speed of about 11,000 revolutions per second). Instead of having a continuous beam of protons, they will be bunched together, into 2,808 bunches to have interactions between the two beams at discrete intervals and never shorter than 25 nanosesond apart.
Before injecting the protons into the main accelerator, they are prepared by a series of systems and their energy is successively increased. The first system called the linear accelerator (Linac 2) generates 50 MeV protons, which feeds the Proton Synchrotron Booster (PSB). The protons, here, are accelerated to 1.4 GeV and then injected into the Proton Synchrotron (PS) to accelerate them further to a energy of 26 GeV. Finally, the Super Proton Synchrotron (SPS) increases their energy to 450 GeV before entering into the main ring, where proton bunches are accumulated, accelerated (over a period of 20 minutes) to their peak 7 TeV energy, and finally stored for many hours (10 to 24) while collisions occur at the four intersection points
Two beams of protons travel at close to the speed of light with very high energies before colliding with each other. The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. The beams are guided around the accelerator ring by a strong magnetic field produced by superconducting electromagnets, which are built from coils of special electric cable operating in a superconducting state, efficiently conducting electricity without resistance or loss of energy.
This requires chilling the magnets to about 271°C – a temperature colder than outer space and is achieved by a distribution system of liquid helium. Just before the collision, another type of magnet is used to ‘squeeze’ the protons closer together to increase the chances of collisions.
All the controls for the accelerator are housed under one roof at the CERN Control Centre. From here, the beams inside the LHC will be made to collide at four locations around the accelerator ring, corresponding to the positions of the particle detectors. In the collider, the oppositely-beaming hadrons will collide at the speed of light. The resulting explosion will create 105 or 100,000 times more heat than the sun in an area a billion or 109 times smaller than a dust-particle.
The total cost of the project is likely to be ranging from €3.2 to €6.4 billion and when in operation, about 7000 scientists from 80 countries, including India, will have access to the LHC. The LHC will produce roughly 15 petabytes (15 million gigabytes) of data annually – enough to fill 100 000 DVDs a year. To have access and analyse this data, CERN is building a distributed computing and data storage infrastructure- the LHC Computing Grid. Physicists hope to use the collider to test various grand unified theories and enhance their ability to answer the following questions:
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Nature of dark matter and dark energy
*Why gravitational force is so many orders of magnitude weaker than the other three fundamental forces?
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Is the popular Higgs mechanism for generating elementary particle masses in the Standard Model realised in nature? If it is so, then, how many Higgs Bosons are there, and what are their masses?
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Do particles have super symmetric (“SUSY”) partners?
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Violations of the symmetry between matter and antimatter.
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According to string theory, there are extra dimensions indicated by theoretical gravitons, as predicted by various models. Can we “see” them?
In addition to the above fundamental research programmes to be conducted by this experiment, it is also linked to spectacular spin offs such as improved cancer treatments, systems for destroying nuclear wastes and an insight into the climate change.
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The physicists at CERN have found that when a beam of protons is fired into the blocks of lead, it generates showers of neutrons. These neutrons can be used to break down the radioactive waste into harmless stable elements.
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It would also help in medical research by treating the cancer with the beams of protons, carbon ions and even antimatter. Although antimatter does not exists naturally but it can be produced in proton synchrotron.
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CERN is also working on investigating the theory that the rate of cloud formation is linked to the level of cosmic rays. As cloud formation is an important part of climate and weather, so the project could find whether other factors besides green house gases are involved in climate changes.
The LHC is going to recreate the natural phenomena of cosmic rays under controlled laboratory conditions, enabling us to study them in more detail. In nature, cosmic rays are particles produced in outer space and some of them are accelerated even to the energies far exceeding those of the LHC. It has been happening for the past billions of years, nature has already generated on Earth as many collisions as about a million LHC experiments. Inspite of all this, the planet still exists.
The Universe as a whole experiences more than 10 million million LHC-like experiments per second. Thus, the possibility of any dangerous consequences is ruled out.
Speculations about microscopic black holes at the LHC refer to particles produced in the collisions of pairs of protons, but each of these has an energy comparable to that of a mosquito in flight. Astronomical black holes are much heavier than anything that could be produced at the LHC.
According to the well-established properties of gravity, described by Einstein’s relativity, it is impossible for microscopic black holes to be produced at the LHC.
Thus, the LHC will generate a bonanza of new experimental data in the coming years to explain the complexities of physics.
The potential breakthroughs include an explanation of what gives mass to fundamental particles and identification of the dark matter that makes up most of the mass in the universe. More exotic possibilities include evidence for new forces of nature or hidden extra dimensions of space and time.
The writer is Professor of Physics, CCS HAU, HISAR
