������

A morning of full immersion in particle physics for a special celebration!

July 4th 2022 has been a special day at CERN, which hosted the celebration ceremony for the 10th anniversary of the discovery of the Higgs boson. Present were many scientists from the experiments, current CERN researchers, and experts from the scientific community in public awareness and engagement.

The important anniversary was celebrated in the morning with a historical symposium featuring eminent scientists: Rolf Heuer (Deutsches Elektronen-Synchrotron (DE)), Lyn Evans (Imperial College (GB)), Peter Jenni  (Albert Ludwigs Universitaet Freiburg (DE)), Eliezer Rabinovici (President of CERN Council), Michel Della Negra (Imperial College (GB)),  Asmeret Asefaw Berhe (Director of the Office of Science, U.S. Department of Energy), François Englert (Nobel Laureate), Katherine Graham (widow of Robert Brout), Peter Higgs (Nobel Laureate), Sally Dawson (BNL), Kerstin Tackmann (DESY), André David (CERN) and Fabiola Gianotti (CERN General Director). Ten years ago, on July 4, 2012, only 2 years after the activation of the largest particle accelerator in the world, the Large Hadron Collider (LHC) at CERN, Joseph Incandela (CMS) and Fabiola Gianotti (ATLAS) announced the simultaneous discovery by their experiments of the Higgs boson. This was a key discovery that altered the history of particle physics.

“The discovery of the Higgs boson was a monumental milestone in particle physics. It marked both the end of a decades-long journey of exploration and the beginning of a new era of studies of this very special particle”

- Fabiola Gianotti

Physicists Robert Brout, François Englert and Peter Higgs had predicted the existence of a all-pervasive quantum field in 1964 to explain how elementary particles gain mass. Their theory predicted that a particles mass is a measure of how much it interacts with that field. Peter Higgs was convinced by his paper reviewers to include the fact that a scalar boson would be associated to the field. Thus the Higgs boson was named nearly 60 years ago.

With the inclusion of this boson, a theory describing the microscopic structure of the universe, dubbed the Standard model, came into being. The ability of this theory to predict the existence and behaviour of new particles has been outstanding. Over the years many new particles were detected and measures. However, the Higgs boson, which was predicted to interact only slightly with the other 16 particles, according to their mass, remained elusive. This was the case when the LHC started taking data in 2010.

Had the Higgs boson not been found, it would have caused a major rethink of the theory and, indeed, some “Higgsless” models were developed by theorists, just in case. Nature, however, put an end to these questions in 2012, with the discovery of the boson by the ATLAS and CMS experiments.

Yet, there are still some phenomena in our universe that are not explained by the Standard Model. In fact, 95% of the universe is made of matter and energy that have yet to be explained, and gravity remains completely removed from the microscopic theory. It is possible, though, that detailed studies of the Higgs boson can help lead to a better understanding of these unknowns.roscopic theory. It is possible, though, that detailed studies of the Higgs boson can help lead to a better understanding of these unknowns.

Since 2012, many tests have been done to investigate in detail the proprieties of this special particle. The mass of the Higgs boson, for example, has been measured to be 125 billion electron volts (GeV), a mass which leads to even more questions and potential answers about physics beyond the Standard Model. Other parameters, such as how strongly the boson interacts with various particles (including itself) have strongly supported the theory put forward by Peter Higgs, Robert Brout and François Englert.

Higgs and Englert won the Nobel Prize for their theory in 2013. Unfortunately, Robert Brout did not live to see the discovery or the prize. Nevertheless, his widow, Katherine Graham, gave a moving and inciteful talk during the symposium.

François Englert and Peter Higgs during the celebration of the discovery on 4^th July 2012, Photograph: Maximilien Brice; Laurent Egli, © 2012-2022 CERN

Why is this particle so important?

What the scientists are trying to do at CERN is to recreate and understand what happened just after the Big Bang, when the elementary particles and their interactions first came into existence. The LHC is currently the only place in the world where the Higgs boson can be produced and studied in deep detail. That’s because of the high energy and luminosity (amount of collisions per second) needed to produce it.

The Higgs boson plays a special role because it interacts with all particles that have mass. That means its properties are closely integrated to the Standard Model and that it could act as a window to physics beyond.

How do we search for the Higgs boson in the detectors?

Using powerful magnets in a 27 km circular tunnel located 100 meters underground, proton beams are accelerated to very high energy in opposite directions, then collided at four different locations. Many elementary particles are generated from collisions (leptons, quarks, W and Z bosons, etc.), which are identified and measured by large, complex detectors that surround the collision points.

Despite the effort, finding a Higgs Boson in these collisions is challenging. Only about 1 in a billion collisions will actually produce one, and only about one in a thousand of them are detected and measured in the ATLAS and CMS detectors. Furthermore, as the boson has an exceedingly short lifetime, one can only be measured by reconstructing the particles it has transformed into. Fortunately, the LHC produces millions of billions of events and the detectors are very precise and efficient.

In the SM, the structure of the vacuum of the universe is intimately related to how the Higgs boson interacts with... itself

André David (CERN)

Slide from the Presentation by Andre David, CERN - 4th July 2022

What is the future of scientific research after the discovery of the Higgs boson?

Higgs boson discovery opens new paths of exploration, provides a unique door into new physics, and calls for a compelling and broad experimental program which will extend for decades at the LHC and beyond

Fabiola Gianotti

Photo 1 Fabiola Gianotti in 2012 presenting the discovery of the Higgs Boson (credit CERN) - Photo 2 Fabiola Gianotti at the Higgs anniversary on July 2022 (credit ������)

Ten years after the discovery, the journey has only started.

The Higgs boson’s self-interaction might hold the keys to a better understanding of the imbalance between matter and antimatter and the stability of the vacuum in the universe. 

Science strives to broaden its horizons not only by trying to find out what lies outside our current model of the universe, but also by contributing to the improvement of the technologies we use at home, including electronics, computing and medicine.

There remain many questions about the universe; maybe some of the answers will be provided by data from the Run 3 of the LHC started on 5^th July 2022, or from the collider’s next major upgrade, the high-luminosity LHC, from 2029 onwards. We will see.

Legenda: , , CERN press release