Project report on

LARGE HADRON COLLIDER

by: Gupta

Submitted Abhishek Electronics and

Communicati on D-2

LARGE HADRON COLLIDER

INTRODUCTION
Large Hadron Collider is the world's largest and highest-energy particle accelerator. It was built with the objective of answering some basic and difficult questions of nature like:

Most important: To smash protons moving at 99.999999% of the speed of light into each other and so recreate conditions a fraction of a second after the big bang. The LHC experiments try and work out what happened. Laws governing the interactions and forces among the elementary objects

The deep structure of space and time intersection of quantum mechanics and general relativity Is the theoretical Higgs mechanism for generating elementary particle masses via electroweak symmetry breaking actually realised in nature? It is expected that the collider will either demonstrate or rule out the existence of the elusive Higgs boson, thereby allowing physicists to determine whether the Standard Model or its Higgsless model alternatives are more likely to be correct. Is supersymmetry, an extension of the Standard Model and Poincar symmetry, realised in nature, implying that all known particles have supersymmetric partners? Are there extra dimensions, as predicted by various models based on string theory, and can we detect them? What is the nature of the dark matter that appears to account for 23% of the mass of the universe? Other open questions which may be explored using high energy particle collisions: 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?

Why is gravity so many orders of magnitude weaker than the other three fundamental forces? Are there additional sources of quark flavour mixing, beyond those already predicted within the Standard Model? Why are there apparent violations of the symmetry between matter and antimatter? What was the nature of the quark-gluon plasma in the early universe?

What is Big bang Theory??

The Big Bang model or theory is the prevailing cosmological theory of the early development of the universe. According to the Big Bang model, the universe was originally in an extremely hot and dense state that expanded rapidly. This expansion caused the universe to cool and resulted in the present diluted state that continues to expand today. Based on the best available measurements as of 2010, the original state of the universe existed around 13.7 billion years ago, which is often referred to as the time when the Big Bang occurred. The theory is the most comprehensive and accurate explanation supported by scientific evidence and observations.

What is Higgs Mechanism??

Higgs mechanism is the process in which gauge bosons (Fundamental particles following BoseEinstein statistics and act as carriers of fundamental forces of physics) can acquire nonvanishing masses through absorption of NambuGoldstone bosons arising in spontaneous symmetry breaking.

DESIGN OF LHC

Location: 175 metres beneath Franco-Swiss border near Geneva, Switzerland Built by: European Organisation for Nuclear Research(CERN) Specifications: Circular tunnel,27 km circumference,Around 1200 dipole magnets, around 400 quadrupole magnets along with 1600 superconducting magnets along with 96 tonnes Helium to keep them at required temperature. The sketch of LHC and its components are as follows:

Here, LHC experiments ATLAS: A Toroidal LHC Apparatus CMS: Compact Muon Solenoid LHCb: LHC-beauty ALICE: A Large Ion Collider Experiment TOTEM: Total Cross Section, Elastic Scattering and Diffraction Dissociation LHCf: LHC-forward MoEDAL: Monopole and Exotics Detector At the LHC LHC preaccelerators p and Pb Linear accelerators for protons (Linac 2) and Lead (Linac 3) Proton Synchrotron Booster PS: Proton Synchrotron SPS: Super Proton Synchrotron DETECTORS Along with above many detectors have also been employed.

There are 6 detectors constructed Two of them, the ATLAS experiment and the Compact Muon Solenoid (CMS), are large, general purpose particle detectors. A Large Ion Collider Experiment (ALICE) and LHCb, have more specific roles and the last two, TOTEM and LHCf, are very much smaller and are for very specialized research.

Detec tor ATLAS CMS ALICE

Description Used to look for signs of new physics, including the origins of mass and extra dimensions. Hunts for the Higgs boson and look for clues to the nature of dark matter. Study a "fluid" form of matter called quarkgluon plasma that existed shortly after the Big Bang. Equal amounts of matter and antimatter were created in the Big Bang. LHCb is trying to investigate what happened to the "missing" antimatter.

LHCb

WORKING OF LHC
The first beam was circulated through the collider on the morning of 10 September 2008. Once or twice a day, as the protons are accelerated from 450 GeV to 7 TeV, the field of the superconducting dipole magnets will be increased from 0.54 to 8.3 teslas (T). The protons will each have an energy of 7 TeV, giving a total collision energy of 14 TeV. At this energy the protons have a Lorentz factor of about 7,500 and move at about 0.999999991 c, or about 3 metres per second slower than the speed of light (c). It will take less than 90 microseconds (s) for a proton to travel once around the main ring a speed of about 11,000 revolutions per second. Rather than continuous beams, the protons will be bunched together, into 2,808 bunches, so that interactions between the two beams will take place at discrete intervals never shorter than 25 nanoseconds (ns) apart. However it will be operated with fewer bunches when it is first commissioned, giving it a bunch

crossing interval of 75 ns. The design luminosity of the LHC is 1034 cm2s1, providing a bunch collision rate of 40 MHz. Prior to being injected into the main accelerator, the particles are prepared by a series of systems that successively increase their energy. The first system is the linear particle accelerator LINAC 2 generating 50MeV protons, which feeds the Proton Synchrotron Booster (PSB). There the protons are accelerated to 1.4 GeV and injected into the Proton Synchrotron (PS), where they are accelerated to 26 GeV. Finally the Super Proton Synchrotron (SPS) is used to further increase their energy to 450 GeV before they are at last injected (over a period of 20 minutes) into the main ring. Here the proton bunches are accumulated, accelerated (over a period of 20 minutes) to their peak 7-TeV energy, and finally circulated for 10 to 24 hours while collisions occur at the four intersection points. All the controls for the accelerator, its services and technical infrastructure 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. CMS detector for LHC The LHC physics program is mainly based on proton proton collisions. However, shorter running periods, typically one month per year, with heavy-ion collisions are included in the program. While lighter ions are considered as well, the baseline scheme deals with lead ions.

The lead ions will be first accelerated by the linear accelerator LINAC 3, and the Low-Energy Ion Ring (LEIR) will be used as an ion storage and cooler unit. The ions will then be further accelerated by the PS and SPS before being injected into LHC ring, where they will reach an energy of 2.76 TeV per nucleon (or 575 TeV per ion), higher than the energies reached by the Relativistic Heavy Ion Collider. The aim of the heavy-ion program is to investigate quarkgluon plasma, which existed in the early universe.

Problems and Challenges

As it is a fact that any mission whether big or small cant be completed without facing challenges. So LHC has also faced many challenges along with delays and accidents during its running. The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the amount of 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 (173 kilograms of TNT). Loss of only one ten-millionth part (107) of the beam is sufficient to quench a superconducting magnet, while the beam dump must absorb 362 MJ (87 kilograms of TNT) for each of the two beams. These energies are carried by very little matter: under nominal operating conditions (2,808 bunches per beam, 1.151011 protons per bunch), the beam pipes contain 1.0109 gram of hydrogen, which, in standard conditions for temperature and pressure, would fill the volume of one grain of fine sand.

Also there were few deaths and leakage of helium gas, vacuum leaks etc which have time to time caused delay.

ACHIEVEMENTS
There have been many achievements of this LHC program that CERN scientists estimate that, if the Standard Model is correct, a single Higgs boson may be produced every few hours. At this rate, it may take about two to three years to collect enough data to discover the Higgs boson unambiguously. Similarly, it may take one year or more before sufficient results concerning supersymmetric particles have been gathered to draw meaningful conclusions. On the other hand, some extensions of the Standard Model predict additional particles, such as the heavy bosons, whose existence might already be probed after a few months of data taking. The first physics results from the LHC, involving 284 collisions which took place in the ALICE detector, were reported on 15 December 2009. The results of the first protonproton collisions at energies higher than Fermilab's Tevatron protonantiproton collisions were published by the CMS collaboration in early February

2010, yielding greater-than-predicted charged-hadron production. After the first year of data taking, the LHC experimental collaborations started to release their preliminary results concerning searches for new physics beyond the Standard Model in proton-proton collisions. So far, no evidence of new particles has been detected. As a result, bounds can be set on the allowed parameter space of various extensions of the Standard Model, such as models with large extra dimensions, constrained versions of the Minimal Supersymmetric Standard Model, and others.

ENHANCEMENTS AND UPGRADATIONS

There is a plan of upgrading LHC to Super LHC by 2018 as any physics experiments tend to give diminishing returns after running for few years. Hence to maintain the luminosity and proper returns upgradation and maintainance is required. It includes increasing the beam current and modifications in ATLAS and CMS.

Thus LHC is one of a great experiment for mankind and its success will throw light on the hidden facts regarding the life.