LHCLARGE HADRON COLLIDER • World’s largest and highest-energy particle accelerator. • Built by the European Organization for Nuclear Research(CERN). • To study high-energy physics & large family of new particles predicted by supersymmetry.
What is HADRON ? • A particle made of quarks held together by strong forces(as e.m. force). • Two types: mesons(made of one quark and one antiquark) and baryons(made of three quarks). • Protons and neutrons are the best known baryons.
DESIGN • Contained in a circular tunnel, with a circumference of 27 km, at a depth ranging from 50 to 175 meters underground. • Crosses the border between Switzerland and France at four points. • Tunnel contains two adjacent parallel beam pipes containing a proton beam, travelling in opposite direction around the ring. • 1232 dipole magnets are used to keep the beams on circular path, while an additional 392 quadrupole magnets are used to keep the beam focused so that the chances of interaction be max.
Approx. 96 tonnes of liquid helium needed to keep the magnets at the operating temperature of 1.9 K(-271.25C). • Six detectors have been constructed at LHC. Two of them, ATLAS and Compact Muon Solenoid(CMS) are large, general purpose particle detectors. • ALICE, LHCb, TOTEM, and LHCf are for very specialized research.
ATLAS consists of a series of concentric cylinders around the interaction point where the proton beams from LHC collide. • Divided into four major parts: • Inner Detector: track charged particles by detecting their interaction with material at discrete points, revealing detailed information about the types of particles and its momentum. • Calorimeters: measure the energy from particles by absorbing it. • Muon spectrometer: an extremely large tracking system, around the calorimeter. Its tremendous size is required to accurately measure the momentum of muons, which penetrate other elements of the detector. • Magnet systems: ATLAS uses two large superconducting magnet system to bend charged particles to measure their momenta. The inner solenoid produces a high magnetic field of 2T which is enough to curve even high energy particles to get the momentum. Its uniform direction and strength allow measurement to be made very precisely.
CMS is designed as a general purpose detector, capable of studying different aspects of proton collision at 14 TeV. • It contains subsystems which are designed to measure the energy and momentum of photons, electrons, muons, and other products of the collisions. • Tracker • Electromagnetic calorimeter • Hadronic calorimeter • Magnets • Muon detector & return yoke
It is optimized to study heavy ion collisions. Pb nuclei collisions will be studied at a center of mass energy of 2.76 TeV per nucleon. • The resulting temperature and energy density are expected to be large enough to generate a quark-gluon plasma, a state of matter where quarks and gluons are deconfined. • The setup has following parts: • Inner Tracking System: it will recognize particles containing heavy quarks by identifying the points at which they decay. • Time Projection Chamber: it is the main particle tracking device in ALICE. • Transition Radiation Detector: electrons & positrons are distinguished from other charged particles using the emission of transition radiation.
4. Photon Spectrometer: made of lead tungstate crystals, it measures the temperature of collision of high energy photons emerging out after striking the crystal. 5. Muon spectrometer: measures pairs of muons, in particular those coming from the decay of upsilon & psi particles. 6. Electro-magnetic Calorimeter: it adds to the high momentum particle measurement capability of ALICE. 7. High Momentum Particle Identification Detector: it determines the speed of particles beyond the momentum range available through energy loss in ITS & TPC. Its range is upto 5 GeV. It is world’s largest caesium iodide detector.
LHCb(Large hadron Collider beauty) • It is a specialized b-physics experiment, particularly aimed at measuring the parameters of CP violation in the interaction of b-hadrons. • After the LHC starts colliding protons at a useful rate for LHCb, in early 2010, LHCb aims to make several measurement on physics phenomena involving B mesons.
TOTEM • It shares intersection points with the Compact Muon Solenoid. • The detector aims at measurement of total cross section, elastic scattering, and diffractive processes.
LHCf • It is a special purpose LHC experiment for astroparticle physics. • Designed to study the particles generated in the forward region of collisions. • Intended to measure the energy and number of neutral pions produced by the collider. This will help explain the origin of ultra high energy cosmic rays.
Purpose and Expected results • Testing various predictions of high-energy particle physics, including the existence of the hypothesized Higgs boson and the large family of new particles predicted by supersymmetry. • Is supersymmetry realized in nature? It will clear up the mystery of dark matter. • To detect the extra dimension if there are any. • To study the nature of the quark-gluon plasma in the early universe. • Why is gravity so many magnitude weaker than other three fundamental forces? • Are electromagnetism, strong and weak nuclear force different manifestation of a single unified force, as per the Grand Unification Theories.
CERN scientists estimates that if the Standard Model is correct, a single Higgs boson may be produced every few hours and may take 2 to 3 years to collect enough data to discover it precisely. Similarly, it may take one year or more to draw meaningful conclusion concerning supersymmetric particles. • Data produced by LHC as well as LHC-related simulation will produce a total data output of 15 petabytes per year.
Safety of particle collisions • Experiments at the LHC have sparked fears that the LHC particle collision might produce doomsdays phenomena, involving the production stable microscopic black holes. Two CERN safety reviews have examined these concerns and concluded that these would decay immediately by means of Hawking radiation, producing all particles in the Standard Model in equal numbers.