CERN: Higgs boson, 10th anniversary of the discovery

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It was exactly 10 years ago, on 4 July 2012, that two groups of physicists at the CERN’s LHC, the ATLAS and CMS collaborations, published simultaneously the discovery of a new particle with properties pointing to it being the Higgs boson, the particle proposed by the Standard Model of the physics of elementary particles, dubbed by the media ’God particle.’ As the CERN stated on the 10th anniversary, this discovery represented a turning point in the history of science. It is due to this that one year afterwards, François Englert and Peter Higgs won the Nobel Prize in physics. Decades earlier, together with the late Robert Brout, they proposed the so-called Higgs field, a field that pervades the entire universe, manifesting itself as the Higgs boson and giving mass to elementary particles.

‘The discovery of the Higgs boson was a monumental breakthrough in elementary particle physics. Simultaneously, it marked the end of several-decade-long research and the dawn of a new era of study of a very unique particle’, says Fabiola Gianotti, general director of the CERN and the spokesperson of the ATLAS experiment at the moment of the discovery. ‘I remember with emotions that day, when the discovery was announced, the day of immense joy for the worldwide community of particle physicists, and for all people, who for decades tirelessly worked to make this discovery possible’.

Throughout ten years from the discovery, physicists made further steps toward understanding the universe – not only did they confirm that the particle discovered in 2012 was truly the Higgs boson, but they have started to paint a picture of how the presence of the Higgs boson, permeating the entire universe, started in the 10th billion part of a second after the Big Bang.

ATLAS and CMS have with impressive preciseness measured that the Higgs boson mass is equal to 125.35 billion GeV. The latter experiments at the LHC have shown that the new particle does not have an intrinsic angular momentum, which physicians call a spin, as the Standard Model predicted for the Higgs boson. On the other hand, all other known elementary particles have a spin, both the particles that the matter consists of, such as up and down quarks which form protons and neutrons and the so-called force carriers, such as W and Z bosons. Additionally, through the analysis of the Higgs bosons decaying into W and Z boson pairs, the ATLAS and CMS collaborations have confirmed that these force-carrying particles receive their mass through the interaction with the Higgs field, as proposed by the Standard Model. The experiments have also corroborated that the up and down quarks, as well as tau leptons – which are the heaviest fermions – get their mass from the interaction with the Higgs field, which was predicted by the Standard Model too.

In the meantime, more than 60 new, complex i.e. composite particles have been discovered at the CERN. Some of them are exotic ’tetraquarks’ and ’pentaquarks’. The experiments have unveiled a series of intriguing implications of a breach in the Standard Model, which necessitate further research, and they have also studied quark-gluon plasma that filled the Universe in the early phase. They have also observed some rare particle processes and opened up the possibility of searching for particles beyond the Standard Model, including the particles that may constitute dark matter.

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What is there more to learn about the Higgs boson and the Higgs field ten years later? As they say at the CERN: a lot. Does the Higgs field give mass to lighter fermions or do some other mechanisms play a role? Is the Higgs boson an elementary or composite particle? Can it interact with dark matter and discover its nature? What generates the mass of the Higgs boson and the self-interaction? Does it have ’twins’?

Not only will finding answers to this and other intriguing questions contribute to our understanding of the universe at the smallest scale, but it will also help us solve some of the greatest mysteries of the universe as a whole. For example, how did the universe become what it is, and what could its final destiny be? It is the very Higgs boson that could hold the key to a better understanding of the disproportion between matter and antimatter, as well as the stability of the vacuum in the universe.

Some of these questions could be answered through data from the upcoming third run of the LHC, or by the planned update of the accelerator, while answers to other enigmas are beyond the reach of the LHC, and necessitate the future ’Higgs factory’. Therefore, the CERN and international partners are researching the technical and financial feasibility of a much larger and more powerful machine, the FCC accelerator, with a circumference of 100 kilometres. Such an accelerator is planned by the new European strategy for particle physics, and it could maintain Europe’s leading role in this field of science.

The CERN marked the 10th anniversary with a range of events, with the central one being the scientific symposium, broadcast and followed in multiple countries. There was a satellite event at the Institute of Physics, Belgrade.

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The Republic of Serbia has been a full member of the CERN since 2019. However, even before this, physicians and institutions from Serbia participated in the work of various collaborations at the CERN. Quite by chance, our researchers took an active part in the CMS and ATLAS experiments, i.e. in the work of both collaborations, which in 2012 proved the existence of the Higgs boson. The Institute of Physics, Belgrade, a national institute of the Republic of Serbia, is CERN’s strategic partner.

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Photo by: CERN