EXP-HEP · Physics Prospects at ALICEat LHC

Final Activity and Management Report Summary - EXP-HEP (Physics prospects at ALICE at LHC)

Physicists around the world have been trying to re-create that soup, known as the Quark gluon plasma (QGP), by slamming together nuclei of atoms with enough energy to produce trillion-degree temperatures. The best way to study the properties of the microseconds-old universe, is not by building a telescope but by building an accelerator quarks and gluons, though they make up protons and neutrons, behave very differently from those heavier particles. Their interactions are governed by a theory known as Quantum chromodynamics (QCD). However, the actual behaviour of quarks and gluons is difficult to study because they are confined within heavier particles. The only place in the universe where QGP exists is inside high-speed accelerators, for the briefest flashes of time. In 2005, scientists at the relativistic heavy Ion collider at Brookhaven National Laboratory (BNL) reported creating QGP by smashing gold atoms together at nearly the speed of light. These collisions can produce temperatures up to 4 trillion degrees - 250 000 times warmer than the sun's interior and hot enough to melt protons and neutrons into quarks and gluons. The resulting super-hot, super-dense blob of matter, about a trillionth of a centimetre across, could give scientists new insights into the properties of the very early universe. So far, they have already made the surprising discovery that QGP is a nearly frictionless liquid, not the gas that physicists had expected. By doing higher-energy collisions, scientists now hope to find out more about the properties of quark gluon plasma and whether it becomes gas-like at higher temperatures. They also want to delve further into the very surprising similarities that have been seen between QGP and ultracold gases (near absolute zero). At the 'Large hadron collider' (LHC) in Geneva, the planning is to double the temperature achieved at Brookhaven, offering a glimpse of an even-earlier stage of the universe's formation. By accelerating and smashing together lead nuclei at the highest possible energies, the ALICE experiment has generated incredibly hot and dense sub-atomic fireballs (which last for a short time), recreating the conditions that existed in the first few microseconds after the big bang. Scientists claim that these mini big bangs create temperatures of over ten trillion degrees. At these temperatures normal matter is expected to melt into an exotic, primordial 'soup' known as quark-gluon plasma. The ALICE ('a large ion collider experiment') is one of the six detectors at the LHC. It is placed in the LHC ring, some 100 metres underground, 16 metres high, 26 metres long and weighs about 10 000 tons. The ALICE collaboration consists of around 1 000 physicists and engineers from about 100 institutes. ALICE utilises state-of-the-art technology including high precision systems for the detection and tracking of subatomic particles, ultra-miniaturised systems for the processing of electronic signals, and a worldwide distribution network of the computing resources for data analysis (the GRID) to process the large amount of data that is recorded as during collisions of lead nuclei, ALICE will record data to disk at a rate of 1.2 GBytes (2 CDs)every second and will write over two PBytes of data to disk. As a Marie Curie fellow at the University of Birmingham, I was involved along with the United Kingdom group in the design, construction and installation of the central trigger electronics (the ALICE Brain) known as the 'Central trigger processor' (CTP) and corresponding software. In ALICE also as in most of the large experiments, triggers are implemented in multiple levels. For the present part of the fellowship, I was involved in setting up the trigger system similar to the one used at the ALICE Experiment and training the manpower to operate and perform various tests using the trigger system. This system is being used in various R&D projects in which our group at university of Jammu is involved. The aim of setting up this trigger system is to fully test the prototype of the detector technologies under study. Implementation of triggers depends on the detector design, and evolving technologies.

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