Newsletter No. 402

No. 402, 4.9.2012 5 high-energy particles so that the resulting explosion would disrupt the field and release Higgs particles which can be detected and whose traces can be analysed. But this Higgs particle, which later came to be called the God particle, had proved elusive. Man proposed, but God was not ready to dispose. This is because the particle accelerators were not yet powerful enough to set loose the Higgs. But the arrival of the much more powerful Large Hadron Colliders (LHCs) in the later part of the 2000s changed all that. The LHC at the European Center for Nuclear Research (CERN) in Geneva, 26.5 km in circumference and 90 m deep in the ground, can smash protons at 99.9999991% of the speed of light, thereby producing fireballs with effervescent particles such as the Higgs and leaving traces which can prove its existence. For some months since the beginning of this year, the scientific community had been holding its breath in anticipation of the tracking and proving of the existence of the God particle. Then in July, the research teams at CERN announced they have found a Higgs-like particle. The whole world erupted in euphoria. But a lot remains to be done. Professor Chu explained, ‘The scientists at CERN would then have to measure the ratio of the different ways of decay of this Higgs-like particle, to see whether the particle is the same as the standard model Higgs. In fact, some of the ways this particle can decay have not been observed yet. So they need to have more events in order to see all the decay modes of the particle.’ Professor Chu estimated that by the end of the year they should have doubled the statistics and so the confidence level would be much higher. Professor Chu continued, ‘If the Higgs particle is indeed found, there are still quite a bit of other new physics that they are looking for at CERN. The most immediate is to test the theory of supersymmetry, which predicts a new class of particles called supersymmetric partners. If they cannot find these particles within the next few years, then the theory of supersymmetry will be in serious trouble, and so will many grand unified theories based on it. If they find these supersymmetric partners, it will be important to characterize them (mass and other physical properties). They may be the so-called “dark matter” in the universe, and their properties have great significance in astrophysics and cosmology as well.’ In Quest of Neutrino Professor Chu is also the leader of the Hong Kong part of an international team in the Daya Bay Reactor Neutrino Experiment, which comprises over 200 scientists from 39 institutes in China, the US, Taiwan, Russia and the Czech Republic. The Daya Bay Experiment will help to answer some of the most puzzling questions about neutrinos. Professor Chu said, ‘Neutrinos are uncharged particles produced in nuclear reactions and are among the lightest elementary particles. The several forms of neutrino morph from one to another but hardly interact at all as they travel through space and matter. Like the Higgs, they are elusive and difficult to detect. In the standard model of particle physics, the neutrinos do not have mass. But now we know they do have a tiny mass, which they may have acquired through interacting with the Higgs particles. While the discovery of Higgs is a confirmation of the standard model, neutrino oscillation (what we study at Daya Bay) is beyond the standard model. So the neutrinos provide a promising window for us to study where the standard model trails off.’ Recently, CUHK has strengthened its collaboration with CERN with the signing of an agreement with the Compact Muon Solenoid Experiment (CMS) at CERN for CUHK scientists and students to take part in the research programme. CMS is one of the two major experiments at CERN and was designed to detect a wide range of particles and phenomena produced in high-energy collisions in the LHC. It therefore plays a part in detecting and confirming the existence of fundamental particles including the Higgs. CUHK students will continue to benefit from research experience gained in the yearly CERN Summer Student Programme. One author remarks, ‘The boson found in the deep tunnel at CERN goes to the very essence of everything.’ (‘The Cathedral of Science’, Time , 23 July, 2012, p. 31) It is this very core of everything that inspires awe and faith in every one of us, scientist or layman. Like the survivor on the spaceship Prometheus in Ridley Scott’s film, man’s quest for the ultimate answer continues. 《停電》 混合媒介布本,36 x 42吋,2012 陳雪兒,2012年畢業於香港中文大學藝術系,同年參加中大藝 術2012本科生畢業展、2012出爐藝術系畢業生聯展、Market Force: Response等展覽。 An Electric Power Cut Mixed media on canvas, 36 x 42 in., 2012 Chan Suet-yi graduated from the Department of Fine Arts, CUHK in 2012. In the same year, she has participated in the CUHK Art 2012 Graduation Exhibition, the Fresh Trend 2012 Art Graduates Joint Exhibition, the Market Force: Response. 緊湊渺子線圈實驗所用的矽晶片追跡系統 CMS silicon tracking detector ©CERN 大型強子對撞機管道 LHC tunnel ©CERN

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