Getting closer to discovering the secrets of the universe

Physicists of the University of Debrecen also participated in the international research that succeeded in measuring the strength of the interaction between the two heaviest known particles, the Higgs boson and the t-quark.

Two experiments of the large hadron collider (LHC) at CERN, ATLAS and CMS reported the discovery of the Higgs boson on  July 4, 2012, independently of each other. The announcement made headlines worldwide then as it confirmed the existence of the last missing particle of the Standard Model after that of the Higgs boson had been theoretically predicted. The discovery simultaneously represented the beginning of an experimental programme with the aim of identifying the features of the new boson. CMS's latest result counts as an important milestone in the programme.

- The visible material of our world is mostly composed of light quarks confined to protons and neutrons and the electrons revolving around them. In the Standard Model the Higgs boson may bind to quarks and leptons, the basic building blocks of matter, with a binding force proportionate to the mass of the particle. The bind has been observed several times through the decay processes of the Higgs boson. However, the mass of t-quark, the heaviest quark, is greater than that of the Higgs boson, hence the decay of the Higgs boson into heavy t-quarks is impossible due to the conservation of energy and momentum, Zoltán Trócsányi, leader of the Particle Physics Research Group of the  University of Debrecen and the Hungarian Academy of Sciences told

The specialists thus needed new methods to measure the strength of the interacion between the two heavy particles. One such opportunity is provided by the joint creation and study of the combination of a Higgs boson, a t-quark, and a t-antiquar. This particularly rare moment was first observed at CMS,  creating one of the primary objectives of the research programme related to the Higgs boson.

From Hungary representatives (researchers and students) of the Wigner Research Institute of Physics of the Hungarian Academy of Sciences, the Lendület CMS Particle and Nuclear Physics Research Group of the Hungarian Academy of Sciences and Eötvös University, the Debrecen Institue of Nuclear Research and the University of Debrecen participated in the cooperation with CMS. The experiments performed made use of the theoretical simulations of the Research Group of Particle Physics of the Hungarian Academy of Sciences and the University of Debrecen for data evaluation.

- Observation of the relationship between the two heaviest particles of the Standard Model represents a big step forward. The observed binding force is in agreement with theoretical expectations but the present precision of the measurement still leaves room for the new physics beyond our knowledge. Processing the multitude of data to be collected in the coming years will lead to better precision, to the Higgs boson uncovering the as yet hiding secrets of high energy physics, a hopeful Professor Zoltán Trócsányi said.

Researchers involved in the CMS experiment published their results in Physical Review Letters on June 4, 2018.

At this week’s LHCP2018 conference the ATLAS cooperation also presents its latest results, where the theoretical simulations developed by  specialists at the University of Debrecen during evaluation of the experimental data.

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Photo: CERN