Later this year, an international community of scientists at the European Organisation for Nuclear Research (CERN), will peep into the heart of matter, in one of the biggest ever experiments in science, the Large Hadron Collider. They are looking for answers to many fundamental questions concerning the nature of matter like how matter gets its mass; what accounts for the dark matter and dark energy that make up for more than 96 percent of the universe; why matter predominates over antimatter in the universe and so on.
Composite matter particles such as protons, neutrons, nuclei of atoms that constitute matter are called ‘hadrons’. The Large Hadron Collider (LHC) is a chain of accelerators in which protons moving with almost the speed of light, collide with each other at four points in a ring-shaped tunnel of circumference 27 kilometres.
The temperature in the minuscule space enveloping the collision can go higher than 100,000 times that in the core of the sun. At that temperature, the colliding particles will be torn apart, freeing their constituent fundamental particles called quarks and gluons to a state as they existed immediately after the Big Bang, which created the universe about 14 billion years ago.
As this state, called the quark-gluon plasma, expands and cools, the quarks and gluons may interact with each other to produce various types of particles, some heavier than the colliding ones, mimicking events in the early universe as predicted by the current theory - the Standard Model of Physics.
Detectors
These massive particles, being highly unstable, decay within billionths of a second, into an avalanche of charged and uncharged particles as well as photons, leaving distinctive trails. Physicists hope that the answers to the above questions may be hiding somewhere in these trails.
Hence, to study the debris in detail, four giant instruments surround the four interaction points. They are designed to capture the various decay products and measure their properties such as energy, mass, momentum, charge. Among them are two general purpose detectors ATLAS (A Toroidal LHC Apparatus) and CMS (Compact Muon Solenoid).
They search for the elusive Higgs boson, which, according to the Standard Model, renders mass to matter and a type of particles called the supersymmetry particles that are supposed to constitute dark matter. ALICE (A Large Ion Collider Experiment), is another big detector designed to study the quark-gluon plasma observing how it progressively gives rise to different types of particles and antiparticles. Detector LHC b will be looking for differences in the decay patterns between these particles to account for the dominance of matter over antimatter in the universe.
Alternatively, these measurements may serve as probes for an entirely new set of concepts and theories. The emerging new physics may not only provide answers to the above questions but also lead to a grand unification of all the fundamental forces of nature, including the gravitational force, which has not been possible under the Standard Model.
The brain of the LHC is the vast computer network. Thousands of physicists from all over the world participate in analysing the huge data. In order to make the data available for all of them simultaneously, tens of thousands of computers are roped in, to form one of the largest networks called the LHC computing grid. This is done in three tiers.
Indian contribution
More than 30 countries, including India, have been participating in these experiments. The Department of Atomic Energy (DAE) signed a protocol in 1996 with CERN. Under the protocol, India provides part of the hardware, software, and manpower worth almost worth 50 million US dollars for the construction and utilisation of LHC.
Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, is the nodal DAE laboratory. The centre has supplied thousands of superconducting magnets, precision magnet positioning systems, control electronics, and so on. It is also involved in the development of novel accelerator technologies for future accelerators like the Compact Linear Collider Test Facility and the Superconducting Proton Linac at CERN. The job involves fabricating vacuum chambers, klystrons, dipole magnets and optics.
Variable Energy Cyclotron Center (VECC), Kolkata, is a Tier 2 laboratory for the ALICE Experiment. It has a 34 Mbps network connectivity under operation since 2004. The Institute of Physics (IOP), Bhuvaneshwar, has developed special types of detectors called Photon Multiplicity Detector and Silicon Multiplicity Detector for the ALICE Experiment. IOP scientists have also carried out detector testing, analysis of test beam data and simulation studies for the LHC.
VECC and the Saha Institute of Nuclear Physics, Kolkata, have designed and fabricated 100,000 MANAS (Multiplexed Analogue Signal Processor) chips, based on indigenous technology for the Dimuon Spectrometer, a part of the CMS experiment. Scientists at the Tata Institute of Fundamental Research (TIFR), Mumbai, have commissioned the outer hadron calorimeter, another part of the CMS experiment, to search for new particles. Scientists from the institute participated in the Magnet Test and Cosmic Challenge of a slice of the CMS detector. They also continued LHC related software and physics simulation activities.
Bhabha Atomic Research Centre (BARC), Mumbai, is developing the Grid View, a software that monitors the flow of data through the huge LHC computer grid. In collaboration with the Bharat Electronics Ltd, BARC has also developed and delivered 1,000 silicon sensors for the measurement of charged particles and gamma rays in the CMS experiment. Based on those measurements, scientists will be able to reconstruct the events subsequent to the production of the quark-gluon plasma and leading to the generation of new particles.
Scientists at the Centre for High energy Physics, Indian Institute of Science, Bangalore, are collaborating on two main areas concerning LHC. Using information from other than LHC, like cosmology and astrophysics, they try to distinguish various models of the new physics and evaluate how the data from LHC complement them. Secondly, they are also carrying out some model-independent studies using data from LHC to understand the fundamental properties of the new physics.
In addition, the Department of Science and Technology and the Nuclear Science Centre, New Delhi, and a number of universities are all participating in various capacities.
