LARGE HADRON COLLIDER(LHC): SEARCH FOR 'GOD PARTICLE'

LARGE HADRON COLLIDER (LHC) : SEARCH FOR ‘ GOD PARTICLE ’

- By Dr. Arun Dixit

At about 10.28 (local time) in the morning, on Wednesday, 10^th September,2008, an exciting experiment took place at the CERN Laboratory, Geneva, Switzerland. It was a giant experiment, known as LHC – Large Hadron Collider - experiment, carried out on the world’s largest machine. It is the first of the series of experiments, which are going to take place in near future. The whole world was anxious to know the outcome of this experiment. The scientists are expecting so many things from this magnificent work. They will be trying to understand how the universe started, what happened shortly after the big bang and also expect to reveal more about the dark matter, dark energy, anti-matter, hidden dimensions of space-matter and the evidence of the hypothetical particles- the Higgs Bosons, to which some people, including some scientists - Nobel winning physicists Leon Lederman is one of them- refer to as the God Particles. The results of LHC experiments will probably change our fundamental knowledge of the universe. Really, very exciting expectations!

On the other hand, there is a hue and cry against this first and the follow up experiments. People have gone to the court of law to get an injunction to this experiment. There are cases pending against it in the Honolulu Federal court of the state of Hawaii, US and in the European Court of Human Rights, Strasbourg, France, pleading that the experiment is going to create black holes on earth, which would grow exponentially and would swallow the whole earth, ending the life on the earth. The human life is at risk, they say. Is it not a very bad situation for every one of us, if the fears of some people come out to be true?

What is this mysterious gigantic experiment? What is this CERN laboratory? what is LHC? What is the cost of this experiment? What is Big Bang and what are these God Particles? Why the people have challenged this experiment in the court of law? In what way, as some fear, it is going to swallow the earth and eliminate the life on this planet. Is it really true that every one of us is going to die if this experiment comes out to be successful? .......these and other several questions, which a layman may ask after reading the news about this experiment. Let us try to address some of them.

What is this CERN?

CERN is a short form of a French name of the research laboratory, the English translation of which is EUROPEAN ORGANIZATON FOR NUCLEAR RESEARCH. Even though this English name is internationally accepted, the original French short form- CERN- is still in use for this research organization. This research organization is situated in Geneva, Switzerland, near the Swiss-French border. It is one of the world’s largest and most respected centers for scientific research. Its business is fundamental physics. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter ------ the fundamental particles and the forces acting between them. By studying what happens when these particles collide, physicists try to learn about the Laws of Nature. From these findings, they are trying to find out what the Universe is made of and how it works.

At the time, when this institution was founded, pure physics research was concentrated on understanding the inside structure of atom, hence the word ‘nuclear’. Today, our understanding of matter goes much deeper than the nucleus, and therefore the main area of research here now is particle physics — the study of fundamental constituents of matter and the forces acting between them. But the word ‘nuclear’ is still retained. CERN is run by 20 European Member States which have special duties and privileges. They make contribution to the capital and operating costs of CERN’s programs and responsible for all important decisions about the Organization and its activities. Some states, for which membership is not possible, are given Observer Status. India and USA, along with other five states, have this Status. There are other 36 states, which are not the members of any kind, are also involved in the CERN programs. Some 8000 visiting scientists, half of the world’s particle physicists, come to CERN for their research .They represent 580 universities and research institutions and 85 nationalities. It is a global endeavor

There is a statue of dancing Lord Shiva at CERN near the building A40, given by the Department of Atomic Energy, India, as a gift, celebrating CERN’s long association with India, which started in the 1960’s and continues strongly today. The statue was unveiled on June 18, 2004. The dance of Shiva is symbolic of the dynamic forces of creation and destruction, and the harmonious balance of opposites. Dance of Shiva is also supposed to be the position of Cosmic forces after splitting.

[ During the first half of the 20^th century, achievements in Europe dominated in physics, from the discovery of the electron to the atomic nucleus and its constituents, from special relativity to quantum mechanics. Sadly, the conflicts of the 1930s and 40s (Second World War) interrupted this, as many scientists had to leave for calmer shores. The return of peace heralded some decisive changes. By the early 50s, the Americans had understood that further progress needed more sophisticated instruments, and that investment in basic science could drive economic and technological development. While scientists in Europe still relied on simple equipments based on radioactivity and cosmic rays, powerful accelerators were being built in the US. Table-top experiments were being overtaken by projects involving large teams of scientists and engineers.

A few far-sighted physicists, such as Rabi, Amaldi, Auger and de Rougemont, perceived that co-operation was the only way forward for front-line research in Europe. Despite fine intellectual traditions and prestigious universities, no European country could cope alone .The creation of a European Laboratory was recommended at a UNESCO meeting in Florence in 1950, and less than three years later, a Convention was signed by 12 countries,and the European Council for Nuclear Research, a provisional body was founded in 1952 with the mandate of establishing a world-class fundamental physics research organization in Europe. When the organization officially came in being in 1954, the Council was dissolved, and the new organization was given the title- European Organization for Nuclear Research, although the name CERN was retained.]

CERN has, to its credit, the following achievements –

1. Nobel Prize to Carlo Rubbia and Simon Van der Meer in physics ( 1984 ) for their discovery of W and Z field particles which are responsible for Weak Interactions, one of the four basic interactions. Their experiments at CERN confirmed the unification of weak and electromagnetic interactions (forces ) , the electroweak theory of the Standard Model. [ We can recall that in 1979, Nobel was awarded to Glashow, Abdus Salam and Steven Weinberg, who established the unification of weak and electromagnetic interactions into one- electroweak interaction and proposed the existence of W and Zfield particles ,the actual experimental discovery of which was confirmed at CERN in 1983-4]

2. Nobel Prize to George Charpak in physics (1992 ) for the development of a particle detector used for exploring the innermost parts of matter.

3. WWW, the World Wide Web was first proposed at CERN in 1989 and further refined in 1990.

4. The Large Hadron Collider (LHC) – Along with other achievements, CERN has come into limelight on 10th September, 2008, when the LHC was declared operational.

The LHC is a circular particle accelerator. It is, therefore appropriate here to know something about particle accelerator.

Particle Accelerator (atom smasher) is an instrument which uses electric field to increase the speed of particles when they passed through it. In the beginning, particles were accelerated in a tube by subjecting it to a high voltage, applied over a gap between a cathode and an anode (the electrodes). This tube is a simple form of an accelerator. It is called as cathode ray tube (CRT) and was conceived at the end of the 19^th century.

The cathode ray tube (CRT) is a vacuum tube containing an electron gun,(a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, and then smashes them into phosphor molecules on the screen .The collisions result in a lighted spot or pixel, on your TV or computer monitor to form images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms (oscilloscope), pictures (television, computer monitor ), radar targets and others. .

A particle accelerator works in the same way, except that they are much bigger in which the particles move much faster (near the speed of light) and the collision results in more subatomic particles and various types of nuclear radiations...It is remarkable to note that the simple accelerators are used in the discovery of the first subatomic particle, electrons. The further developments in understanding the inner structure of the atom is done with the help of higher form of accelerators .The developments we see in the field of electronics is because of the accelerators only. The Accelerators are also most commonly used for external beam radiation treatments for patients with cancer. It can also be used in radio surgery similar to that achieved using the gamma knife on targets within the brain. It delivers a uniform dose of high energy x-ray to the region of patient’s tumer.

In advanced form of particle accelerators, the speed of the particles is continuously increased by using electric fields and magnets. As the speed of the particle increases, the energy of the particle also increases. The speed of the particle can be increased to such a high level that it nearly reaches the speed of light but not equal to that of light, the limit which is imposed by Einstein’s theory. When particles with such a high speed and with such a high energy collide with each other, they are broken down ( smashed) in to fragments. The study of these fragments gives a wealth of information to the scientists which they can analyze and use for their research.

Accelerators are of two types : a) Linear and (b) Circular

(a) Linear accelerator (linac) is the simplest type of accelerator. Fundamentally, it is a long tube through which charged particles are passed and accelerated. In linac, a great many electrodes are separated by a small gaps. Stanford University has the largest linear accelerator ( 50 GeV), named as Stanford Linear Accelerator Center (SLAC). It is about 3 Km in length. The research at SLAC has produced three Nobels in Physics for the discoveries of for charm quarks(1976), quark structure inside proton and neutron(1990), the tau lepton(1995).

At the international level, it is planned to build a huge International Linear Accelerator (ILC), which would have an initial capacity of 500GeV (see below * ), which could be steadily increased to 1000GeV ( 1TeV). Its length is expected to be between 30 to 40 Km. It was to be built at the Fermi Lab ,Illinois ,US. where the cyclotron,, Tevatron is situated, but because of the inability of the US govt. to provide necessary funding to build it in the US, the location of the proposed accelerator is not fixed, even though its design is finalized in Feb.2007 And hence the execution of this project is pending.

[* Energy of a particle is measured in terms of an unit – electron volt. It is the smallest unit of energy and defined ‘as the amount of kinetic energy gained by a single unbound electron when it accelerates through an electrostatic potential difference of one volt’ , which has the value as: 1eV = 1.6 ^-19 J. The masses of elementary particles are frequently expressed in term of electron- volts by making use of Einstein's famous equation, E = mc² , where m is the mass of the particle and c is the speed of light.

The bigger units of energy are as follow:

1 thousand (Kilo-K) = 1000 (10⁺³) ; 1 million (Mega-M)= 1000 of a thousand=10 lakh (10⁺⁶ ) ;

1 billion (Giga-G) = 1000 of a million =100 crores(10⁺⁹) ; 1 trillion (Tera-T) =1000 of a billion ( 10⁺¹²)

10⁺³ eV = 1 KeV 10⁺⁶ eV = 1 MeV

10⁺⁹ eV = 1 GeV 10 ⁺¹² eV = 1 TeV. ]

(b) Circular Acclerators are also called as Cyclotron, which are circular in shape. Circular geometry is preferred for hadron (e.g. protons, neutrons, etc ) collisions. The electrodes are supplied with an alternating current that attract and repel the particles, thus accelerating the particles. This type of accelerator is much easier to make than a few miles of linear accelerator. Large electromagnets are used to keep the accelerated particles in circular motion. The first cyclotron was conceived by Earnest Lawrence in 1929. Neutrons are neutral in nature and therefore, different techniques are used to accelerate them.

The Tevatron, was considered to be the largest circular accelerator in the world before the LHC came in to existence. The Tevatron is established by the Fermi lab in Batavia, near Chicago, Illinois, USA. It has a circumference (length) of 6.28 Km. It is an accelerator capable of colliding proton and an anti-proton at a combined energy of 2 T eV (1TeV each). Tevatron is linear in the beginning which then becomes circular. In 1995, it announced the discovery of the Top Quark. Dr Rajendra Raja, the Indian born US scientist was a leading person in this experiment. The experiment was done by colliding protons and antiprotons traveling in opposite direction, at almost the speed of light. The longer the accelerator runs and the more data it accumulates, the better its chances of finding something new. So by the summer of 2009, the Travetron may have several times more total data than its new competitor i.e. the LHS.

THE FEATURES OF THE LARGE HADRON COLLIDER ( LHC) :

1. The LHC is the biggest accelerator in the world. Its cost is about $ 10 billion ( = $ 1000 crores )

2. About 10,000 scientific workforce is working on this project. Prof. Lyn Evans is the present Director ofLHC and Prof. Robert Aymer is the present director general of the CERN.

3. The LHC, is the longest circular tunnel in the world. Its circumference is 27 Km and its diameter is 3.8 Meters. This instrument is situated nearly100 meters below the surface of the earth. It is lined with concrete from outside. The construction was completed between 1983 to 1988.

4. The Biggest refrigerator in the world. There are total 9300 magnets inside the collider. All the magnets are pre-cooled to a lower temperature of -193.2 °C using 10,000 tonnes of liquid nitrogen. They are further cooled to - 271.3 °C by adding 60 tonnes of liquid Helium. Because of this low temperature, the magnets become superconductor and therefore there are almost no losses in conduction. This is the lowest temperature ever attained. It could hold 150000 fridges full of sausages at a temperature colder than deep outer space.

5. The Emptiest space in the system. The inner tunnel is nearly evacuated, comparable to outer space. The particles travel in an ultra high vacuum, a cavity as empty as the interplanetary space. The internal pressure is very low and equal to 10^-13 atmosphere. Because of this very low pressure, the particles do not collide with the residual gas molecules.

6. Speed of Light. The particles are continuously accelerated by the super cooled magnets so that the trillions of protons will race around the accelerator ring 11,245 times a second. The final speed of the particles is 99.9999% of the speed of light.

7. The maximum energy of a single proton will be 7 TeV and when the two oppositely moving protons collide with each other , the combined collision energy will be 14 TeV.

8. Atogether some 600 million collisions will take place every second.

9. The Hottest spot in the world. The LHC is a machine of extreme hot and cold. When the two beams of protons collide, they will generate temperatures more than 100 000 times hotter than the heart of the Sun, concentrated within a minuscule space. So there are two extreme temperatures working in the same machine. At the points where the high energy protons collide, there is a very high temperature, while the magnets which accelerate the protons are kept at the lowest temperature.

10. Particles used : For initial experiments proton – proton collisions are used but in later stage experiments, heavy ions like Lead will be used.

11. When protons arrive in the LHC they are traveling at 0.999997828 times the speed of light. Each proton goes around the 27Km ring over 11 000 times a second.

12. How many collisions? In an accelerator, particles collide with each other. In LHC, two streams of high energy protons are meeting which are coming from opposite directions. Even though the two streams are approaching each other, all the protons do not collide with each other. If two bunches of protons meet head on, the number of collisions between protons of one beam and protons from the other beam might be ten, one or even zero. How often are there actual collisions? For a fixed bunch size , this depends on how many protons are there in each bunch, and how large each proton bunch is. Actually a proton can be roughly of as being about 10^-15 meter in radius. If you had bunches 10^-6 meters in radius, and say there are only10 protons in each bunch ,the chance of even one proton-proton collision when two bunches met ,would be extremely small. On the other hand, if each bunch had a billion-billion (10^{+ 18}) protons so that its entire cross section was just filled with protons, every proton from one bunch would collide with one from the other,and you would have a billion-billion collisions per bunch crossing. The LHC situation is in between these two extremes, a few collisions ( up to 20 ) per bunch crossing, requires about a billion protons in each bunch. The accelerator can fire 300 bunches of 100 billion protons each, with the same number fired in the opposite direction, which will cause up to 40 million collisions at each of the four interaction sites.

13. The Storage Ring: For some applications , it is useful to store beams of high energy particles for some time without further acceleration. This is especially true for colliding beam accelerators, in which two beams , moving in opposite directions, are made to collide with each other. They , therefore are stored in a device called as storage ring. A storage ring is the same thing as a cyclotron, expect that it is designed just to keep the particles circulating at a constant energy, for as long as possible, not to increase their energy any further. However, the particles must still pass through at least one accelerating cavity each time they circle the ring, just to compensate for the energy they lose due to radiation.

14. Detectores : To sample and record the results of up to 600 million proton collisions per second, physicists and engineers have built huge and bulky devices that measure particles with micron precision.The LHC’s detectors have sophisticated electronic trigger systems that precisely measures the passage time of a particle to accuracies in the region of a few billionths of a second. The trigger system also registers the location of the particles to millionth of a meter. This incredibly quick and precise response is essential for ensuring that the particle recorded in successive layers of a detector is one and the same.

Detectors are the tools that particle physicists use to "see" the products of a collision.

Each collision seen by the detector is called an event. Three basic types of detectors observe the particles in an event : tracking detectors record the path of a particle, calorimetric detectors absorb particles and measure their energy and particle identification detectors identifie the type of particles . Physicists assemble these detectors in layers around the collision point.

There are four detectors placed at four different places in the LHC ring. Their names are –LHCB, CMS, ALICE and ATLAS. These four detectors serve different purposes and detect different particles.

LHCB --- looks for difference between matter and antimatter. CMS -- general purpose detector

ALICE ---detects quarks and gluons. ATLAS --- general purpose detector like CMS and looks for the evidence of Higg’s Bosons , extra dimensions and dark matter.

ATLAS is about 45meters long and more than 25 meters high and weighs about 7000 tons.

[ATLAS Detector]

The data recorded by each of the big experiments at the LHC will fill around 100 000 dual layer DVDs every year.To allow the thousands of scientists scattered around the globe to collaborate on the analysis over the next 15 years ( the estimated life time of the LHC ), tens of thousands of computers located around the world are being harnessed in a distributed computing network called Grid.The results of the experiment will be analysed by the LHC Grid – a network of 60,000 computers .You can think each experiment as a giant digital camera with around 150 millions of pixels taking snapshots of 600 millions times a second. Data worth 15 petabytes is to be analysed [1 peta bytes ≈ 1000⁺⁵ ; google processes about 20 peta bytes of data a day ] In a gigantic underground race track, tiny particles speed in a circle, just to crash into each other head-on. The Idea of this is to simulate nothing less than the beginning of our universe.The LHC explores the area of fundamental particles and therefore, it is proper here to know something about them.

Fundamental Particles:

We all know that everything around us is made up of matter particles, which are called as atom. By the year 1932, the popular model of an atom was evolved. In this spherical model of an atom, all protons (p) and neutrons(n) are packed in a very tiny space called‘ nucleus’ which is surrounded by electrons(e) at different orbits, at different energies. The radius of the nucleus is around 10^{- 15} meter and the radius of the atom is about 10^-10 meter , i.e. 10⁺⁵ times longer than that of a nucleus. If we consider the radius of the nucleus as 1 cm, then outer radius of the atom will be about 1 Km. The space between the nucleus and the outer boundary of the atom is almost empty, in which electrons revolve in definite circles, which are called as orbits.

The particles, p, n and electron-e are called as the sub – atomic particles and they were supposed to be indivisible. But this assumption was proved to be incorrect. They are not the fundamental particles but they are also composed of still smaller particles which are more fundamental in nature. This was possible because of the accelerators. We have seen that the cathode ray tube, which is a primitive form of an accelerator, was used by J. J. Thomson to discover the first elementary particle, electron. Higher generations of accelerators are used in discoveries of other elementary particles. The particles can be created , accelerated and made to collide with each other in accelerators. The collisions of such high speed particles, smash them into smaller particles, which are more elementary than their parents. Thus accelerators are used to create and identify more and more elementary particles. More than one hundred particles have been so far identified with the help of accelerators. It is also called as the ‘particle zoo’.

Are all these so called ‘elementary particles’ really fundamental in nature ? The answer is, no .

They are also made up of smaller particles. It is suggested that many of the particles in the particle zoo are made up of two basic types of particles, called Quarks and Leptons. There are six types of quarks and six types of leptons, all of which are called as ‘Fermions’. They are called Fermions because they obey the Fermi-Dirac statistics. All the ‘Fermions’ have half integer spin ( ½ ). Each fermion has its own distinct antiparticle. All 12 fermions have equal number of anti- particles, making the total of basic particles equal to 24.

The six Quarks are as follow :

Quark : Up Down Charm Strange Top Bottom

Charge : +2/3 -1/3 +2/3 -1/3 +2/3 -1/3

On the basis of the charges on the quarks, we can find the charges on the proton and neutron.

1 Proton = 2u+1D = 2 x (+2/3 ) +1x (-1/3) = +4/3 – 1/3 = 3/3 = + 1 charge.

1 Neutron = 2d + 1u = 2 (-1/3) + 1 ( +2/3) = -2/3 + 2/3 = 0 charge.

FUNDAMENTAL FORCES : A fundamental interaction or fundamental force is a mechanism by which matter particles interact with each other. There are four fundamental forces at work in the Universe :

1. The Strong Force, 2. The Weak Force , 3. The Electromagnetic Force, 4. The Gravitational Force.

These forces work over different ranges and have different strengths. The weak and strong forces are effective only over a very short range and dominate only at the level of subatomic particles. Gravity is the weakest force but it has an infinite range. The electromagnetic force also has infinite range but it is many times stronger than the gravity ( e.g. cosmic rays). The strong force is the strongest among all the four fundamental forces.

BOSONS : We have seen that the matter particles interact with each other through the fundamental forces. These fundamental forces result from the exchange of force carrier particles. These force carrier particles belong to a group of particles called as Bosons. Matter particles transfer discrete amount of energy by exchanging bosons with each other. Each fundamental force has its own corresponding boson particle , e.g. the strong force is carried by the boson particle named as ‘ gluon’ and so on, which is clear in the following table. The gluon, photon and W/Z particles are identified but the gravitons are not yet found, they are only postulated. All the bosons have integer spin.

Interaction (force)	Mediator ( Particles)	Relative Strength	Range
1. Strong Nuclear	gluon	1038	10-15
2. Electromagnetic	photon	1036	infinite
3. Weak nuclear	W ( W+, W- ) & Z Bosons	1025	10-18
4. Gravitational	Graviton	1	infinite

Gluon, photons and W,Z particles are called as Gauge Bosons, which are originated from the Gauge Theory. Graviton and one more type of bosons - Higg’s boson, are other two types of bosons, which are theoretically anticipated but which are not yet discovered.

STANDARD MODEL OF PARTICLES AND FORCES :

Physicists have developed a theory called The Standard Model that explains what the world is and what holds it together. It is a collection of theories that embodies all of our current understanding of fundamental particles and forces. Developed in the early 1970s, this model has successfully explained experimental results and precisely predicted a wide variety of phenomena occurring in the Universe. It is a simple and comprehensive theory that explains all the hundreds of particles and complex interactions with only :

6 quarks and their 6 anti- particles, 6 leptons and their 6 anti- particles and Force carrier particles - Photons, gluons, W & Z Bosons.

The Standard Model falls short of being a complete theory of fundamental interactions, primarily because of its lack of inclusion of gravity, the fourth known fundamental interaction.

Higg’s Bosons : One part of the Standard Model is not yet well established. We do not know what causes the fundamental particles to have masses. The simplest idea is called the Higgs mechanism. Prof. Peter Higgs, professor at the Edinburgh University, proposed a theory which envisages a new type of particles, in 1964. This mechanism involves one additional particle, called the Higg’s boson, and one additional force type, mediated by exchanges of this boson.Large Hadron Collider at CERN, is intended to search for the Higgs particle ( God Particles).

UIFICATION MODEL OF FORCES : As an extension of the Standard Model, Physicists are trying to find out an unified theory of the forces. It is believed that in the incredibly high energy conditions of the big bang (10^-34 s after the big bang) there was a single superforce governing all particle interactions. As the Universe cooled, this force split into the four ‘fundamental’ forces as described earlier. Therefore, at high enough energies the particle interactions for the different forces should behave the same, and the different forces are really just low energy manifestations of a single force. It is an ultimate goal of particle physics to produce a theory of a superforce which also explains all four forces seen at low energies. Developing this ‘Theory of Everything’ is a challenge before the scientists.

MAIN GOALS OF THE LHC :

Our current understanding of the Universe is incomplete. The Standard Model of particles and forces summarizes our present knowledge of particle physics. The Standard Model has been tested by various experiments and it has proven particularly successful in anticipating the existence of previously undiscovered particles. However, it leaves many unsolved questions, which the LHC will help to answer.

1. The Standard Model does not explain the origin of mass, nor why some particles are very heavy while others have no mass at all. The answer may be the so-called Higgs mechanism. According to the theory of the Higgs mechanism, the whole of space is filled with a ‘Higgs field’, and by interacting with this field, particles acquire their masses. Particles that interact intensely with the Higgs field are heavy, while those that have feeble interactions are light. The Higgs field has at least one new particle associated with it, the Higgs boson. If such a particle exists, experiments at the LHC will be able to detect it.

2.The Standard Model does not offer a unified description of all the fundamental forces, as it remains difficult to construct a theory of gravity similar to those for the other forces. Supersymmetry — a theory that hypothesises the existence of more massive partners of the standard particles we know — could facilitate the unification of fundamental forces. If supersymmetry is right, then the lightest supersymmetric particles should be found at the LHC.

3. Cosmological and astrophysical observations have shown that all of the visible matter accounts for only 4% of the Universe. The search is open for particles or phenomena responsible for dark matter (23%) and dark energy (73%). A very popular idea is that dark matter is made of neutral — but still undiscovered — supersymmetric particles.

The LHC will also help us to investigate the mystery of antimatter. Matter and antimatter must have been produced in the same amounts at the time of the Big Bang, but from what we have observed so far, our Universe is made only of matter. Why? The LHC could help to provide an answer.LHC the guide

4. In addition to the studies of proton–proton collisions, heavy ion collisions at the LHC will provide a window onto the state of matter that would have existed in the early Universe, called ‘quark-gluon plasma’. When heavy ions collide at high energies they form for an instant a “fireball” of hot, dense matter that can be studied by the experiments.

5. Are electromagnetism, the strong nuclear force and the weak nuclear force just different manifestations of a single unified force, as predicted by various Grand Unification Theories?

6. Why is gravity so many orders of magnitude weaker than the other three fundamental forces? See also Hierarchy problem.

7. Are there extra dimensions, as predicted by various models inspired by string theory, and can we detect them?

.[ Stephen Hawking said in a BBC interview that "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 one hundred dollars that we won't find the Higgs." In the same interview Hawking mentions the possibility of finding super partners and adds that "whatever the LHC finds, or fails to find, the results will tell us a lot about the structure of the universe."]

WORKING OF THE LHC :

LHC is the world’s biggest accelerator and the biggest machine ever made. It is an outcome of the collective efforts of the world scientific community and common political will of the governments of majority of the countries of the world. No one country can do such a big adventure individually .The actual working of the accelerator is complicated, it can be explained in simple term as :

The LHC accelerates two beams of atomic particles ( hadrons= proton or lead nuclei) in opposite directions around the 27km collider. When the two particle beams reach their maximum speed ( near to that of light), the LHC allows them to ‘collide’ head on at 4 points on their circular journey. When two protons collide, they break apart into even smaller particles. That includes subatomic particles called quarks and a mitigating force called gluon. Quarks are very unstable and will decay in a fraction of a second. Thousands of new particles are produced when particles collide and detectors, placed around the collision points, allow scientists to identify these new particles by tracking their behaviour. The detectors are able to follow the millions of collisions and new particles produced every second and identify the distinctive behaviour of interesting new particles from among the many thousands that are of little interest.The detectors collect information by tracking the path of subatomic particles. Then the detectors send data to a grid of computer systems.

Physicist will use the LHC to recreate the conditions just after the Big Bang, by colliding the two beams head-on at very high energy. As the energy produced in the collisions increases, researchers are able to peer deeper into the fundamental structure of the Universe and further back in its history.

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