Research: Particle Collisions Return with World Record Energies when the Higgs Boson Turns 10 Years Old

2022-07-01

July 4 marks 10 years since the announcement of the Higgs boson discovery in data from the Large Hadron Collider (LHC), the World’s largest and most powerful particle accelerator at CERN, in Geneva. The day after the 10th anniversary, on July 5, the LHC will re-start after a few years of shut-down, with record energies of 13.6 TeV.

The Large Hadron Collider, LHC, at CERN in Switzerland was shut-down during more than three years for planned maintainence and upgrades. In the upcoming data-taking period, which goes under the name Run 3, more proton collisions are planned over a period of four years with record energies of 13.6 TeV (13.6 x 1012 electron volts).

Proton beams collide with each other at the LHC experiments, and in these collisions, Higgs bosons are created. The Higgs boson was observed for the first time 10 years ago by the ATLAS and CMS experiments at the LHC. Several physicists at Uppsala University work in the ATLAS Collaboration, together with around 3 000 other researchers, students and engineers from around the World. Several hundred of these perform their research on the Higgs boson.

“The Higgs boson is 10 years old, but we are still getting to know it. During the upcoming years we will be able to use it as a tool for discoveries beyond the Standard Model,” says Rebeca Gonzalez Suarez, researcher at the Department of Physics and Astronomy and member of the ATLAS Collaboration.

The image shows a proton-proton collision in the ATLAS detector where one pair of b-quarks and one pair of tau-leptons are produced. Such an event can occur when two Higgs bosons are created simultaneously, but can also come from other background processes. Credit: ATLAS.

The Higgs boson is a basic building block of the Standard Model, connected to the origin of mass via what is called the Higgs mechanism. Since its discovery, researchers have been able to measure its properties, such as mass, spin and couplings to other particles, with increasing accuracy. They have been able to do this by analysing proton-proton collisions in the large ATLAS and CMS detectors at the LHC. The Higgs boson decays into other particles right after it is created, and these particles leave traces in the detectors that can be studied.

A condition for the Higgs boson’s existence is that it couples to itself. To observe pairs of Higgs bosons is therefore necessary to further study the mechanism that explains the origin of mass, but also to gain a better understanding of the Universe. However, the probability of creating pairs of Higgs bosons is very small and requires very large amounts of data.

If two Higgs bosons produced simultaneously were observed more often than what the Standard Model predicts, it would be clear evidence for new phenomena beyond the Standard Model. In addition, the properties of Higgs boson pairs can help answer questions about, among other things, the nature of the Higgs boson itself, and the vacuum stability of the universe.

There are many indications that the Standard Model is not a complete theory, as there are many questions set by experimental data that it cannot explain, such as why neutrinos have mass and the presence of dark matter and dark energy. Nor can it explain the differences between particles and antiparticles that arouse at the birth of the universe. During Run 3, the higher energy and luminosity will allow for scientists to explore the Standard Model and possibly learn about these questions.

“In Run 3 we will be able to explore the Standard Model a little bit more and maybe learn a little bit more about what we are not yet able to understand,” says Arnaud Ferrari, professor at the Department of Physics and Astronomy, who also works in ATLAS.

The Discovery of the Higgs Boson

In 2013, Englert and Higgs were awarded the Nobel Prize in physics for the theory that explains how elementary particles obtain their mass. Englert and Higgs proposed the theory independent of each other as early as 1964 but it was confirmed only in 2012 when the Higgs boson was discovered. In the theory, the origin of the mass of almost all elementary particles is explained by a universal, so-called Higgs field, which permeates the vacuum and interacts with some of the elementary particles. To measure the properties of the Higgs field will then also contribute to our understanding of the creation of the Universe.

Contact

Arnaud Ferrari, professor at the Division for High Energy Physics, the Department of Physics and Astronomy, arnaud.ferrari@physics.uu.se, 018-471 5827.

Rebeca Gonzalez Suarez, researcher at the Division for High Energy Physics, the Department of Physics and Astronomy, rebeca.gonzalez.suarez@physics.uu.se, 018-471 7390, 0708-921926.

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Camilla Thulin

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Last modified: 2022-07-18