Large Hadron Collider generates mini Big Bangs
The Large Hadron Collider (LHC) has achieved its goals for 2010 and embarked on a new phase of activity which will see scientists probe the kind of matter that existed just after the Big Bang. For the past seven months, scientists working on the LHC at CERN (the European Organization for Nuclear Research) have been studying collisions between protons. Their main goal was to achieve a 'luminosity' (a measure of the collision rate) of 10 to the power of 32 per square centimetre per second, something they managed on 13 October, 2 weeks ahead of schedule. This proton phase of the experiment ended on 4 November. Results generated during this period include the validation of certain aspects of the Standard Model of particles and forces at high energies, the first observations of the top quark in proton-proton collisions, and the limits set on the production of new particles such as 'excited' quarks. 'This shows that the objective we set ourselves for this year was realistic, but tough, and it's very gratifying to see it achieved in such fine study. It's a testimony to the excellent design of the machine as well as to the hard work that has gone into making it succeed,' commented CERN Director General Rolf Heuer. 'It bodes well for our targets for 2011.' The LHC has already started its next phase of activity, which involves smashing lead ions into each other at record energies in a bid to recreate the kinds of conditions that existed in the first moments of the Universe's existence. The first collisions between lead ions have already taken place, to the excitement of scientists working on the ALICE experiment - one of four experiments running at the LHC. 'We are thrilled with the achievement! The collisions generated mini Big Bangs and the highest temperatures and densities ever achieved in an experiment,' exclaimed Dr David Evans of the University of Birmingham in the UK. 'This process took place in a safe, controlled environment generating incredibly hot and dense sub-atomic fireballs with temperatures of over 10 trillion degrees, a million times hotter than the centre of the Sun,' he added. 'At these temperatures even protons and neutrons, which make up the nuclei of atoms, melt resulting in a hot dense soup of quarks and gluons known as a quark-gluon plasma. 'By studying this plasma, physicists hope to learn more about the Strong Force, one of the four fundamental forces of nature. The Strong Force not only binds the nuclei of atoms together but is responsible for 98% of their mass. I now look forward to studying a tiny piece of what the universe was made of just a millionth of a second after the Big Bang.' Another success for the LHC is the way the Worldwide LHC Computing Grid (WLCG) coped with the immense amounts of data generated during the proton-running phase of the experiment. The WLCG draws on the computing power of over 140 computer centres worldwide to support the experiments at the LHC. The system handles over a million computing jobs per day, and data transfer rates have reached 10 gigabytes (the equivalent of 2 whole DVDs of data) per second. The lead-ion experiments now taking place at the LHC will pose new challenges for the WLCG, as they will generate a greater flow of data than the proton-proton collisions. Tests have demonstrated that CERN's data storage system should be able to cope with this data flow. The lead ion experiments are scheduled to run until 6 December, when the LHC will shut down for maintenance. It will start working again in February with a return to proton collisions.
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