10 years have passed since the discovery of the Higgs boson

Exactly ten years ago, on July 4, 2012, collaborations ATLAS s cms in the Large Hadron Collider (LHC) at CERN announced the discovery of a new particle with characteristics consistent with those of Higgs’ Boson. The discovery was a milestone in the history of science and caught the world’s attention.

A year later, he honored François Englert s peter higgs with him Nobel Prize in Physicssince already in the 1960s, and along with the end Robert Broutpredicted the existence of a new fundamental field, known as higgs fieldthat fills the universe, manifests as the Higgs boson and gives mass to elementary particles.

The discovery of the Higgs boson was a monumental milestone in particle physics, marking the end of a long research path that spanned decades and the beginning of a new era.

Fabiola Gianotti (CERN Director General)

“The discovery of the Higgs boson was a monumental milestone in particle physics. It marked the end of a long research path that lasted decades and the beginning of a new era of studies focused on this very special particle”, he explains. Fabiola Gianotti, director general of CERN and spokesperson for the ATLAS experiment at the time of the discovery. “I look back with emotion on the day of the announcement, a day of immense joy for the global particle physics community and for all the people who have worked tirelessly for decades to make this discovery possible.”

How has the trip been so far?

The new particle discovered by the ATLAS and CMS international collaborations in 2012 resembled the Higgs boson predicted by the standard model. But was it really that much sought after particle? Once the discovery was made, both collaborations began to investigate in detail whether the properties of the particle they had discovered actually matched the characteristics predicted by the model.

Using data collected during the decay phenomenon of this new particle in two photonsexperiments showed that this new particle has no intrinsic angular momentum, or quantum rotation, which is in agreement with the predictions of the Higgs boson obtained with the standard model. In contrast, all other known elementary particles have spin.

Experiments have shown that the Higgs boson has no intrinsic angular momentum, or quantum spin, that matches the predictions of the Standard Model.

On the other hand, observing that Higgs bosons are produced and decay in pairs of W or Z bosonsATLAS and CMS confirmed that the latter acquire their mass through their interactions with the Higgs field, as predicted by the standard model.

Experiments also showed that the top quarkThe quark bottom it’s him tau lepton, which are the heaviest fermions, get their mass from their interactions with the Higgs field, again as the model predicts. These observations also confirmed the existence of an interaction or force called yukawa interactionwhich is part of the standard model, but is different from all other forces: it is mediated by the Higgs boson and its force is not quantized, that is, it is not given by multiples of a given unit.

ATLAS and CMS measured the mass of the Higgs boson, resulting in a value of 125 billion electron volts (125 GeV), with an impressive accuracy of almost one per thousand. Knowing this value is important because, along with the mass of the heaviest elementary particle known, the top quark, and other parameters, the mass of the Higgs boson can help us determine the stability of the universe in a vacuum.

Lots of research ahead

What remains to learn about the Higgs field and the Higgs boson ten years later? Much. Does the Higgs field also give mass to the lighter fermions, or could there be another mechanism at play? Is the Higgs boson an elementary or composite particle? You can interact with dark matter and reveal the nature of this mysterious form of matter? What generates the mass of the Higgs boson? Do you have ‘twins’ or ‘relatives’?

Finding the answers to these and other questions will not only contribute to our understanding of the universe at its smallest scales, but will also help us unravel some of the biggest mysteries the universe as a whole holds, such as how it came to be. what it is like and what its final destination could be.

“The Higgs boson itself could point to new phenomena, including some that may be responsible for the dark matter in the universe,” says the CMS spokesperson, Luca Malgeri. “ATLAS and CMS are doing a lot of research to investigate all sorts of unexpected processes involving the Higgs boson.”

The Higgs boson itself could point to new phenomena, including some that may be responsible for the dark matter in the universe.

Luca Malgeri (CMS Spokesperson)

While answers to some of these questions may be provided by data collected during the LHC’s upcoming and impending Run 3 or later periods of accelerator operation, the answers to other puzzles are believed to lie beyond the LHC’s reach, requiring a future “Higgs factory”. “. For this reason, CERN and its international partners are investigating the technical and financial feasibility of a much larger and more powerful machine, the Future Circular Collider (FCC).

“High-energy colliders remain the most powerful microscope we have for exploring nature at the smallest scales and discovering the fundamental laws that govern the universe,” says Gian Giudice, head of the Theory Department at CERN.

Spanish participation in the discovery of higgs

The Spanish research community played and continues to play a very important role in the ATLAS and CMS collaborations at CERN, the experiments that announced the sighting of the Higgs boson on July 4, 2012.

Since the launch of the ATLAS detector, researchers at the Institute of High Energy Physics (IFAE), Institute of Corpuscular Physics (IFI), Barcelona Microelectronics Institute (IMB-CNM) and the Autonomous University of Madrid (UAM).

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On the other hand, the national presence also stands out in the CMS program since the beginning of this experience. The groups of the Center for Energy, Environmental and Technological Research (CIEMAT), Institute of Physics of Cantabria (IFCA), Autonomous University of Madrid (UAM) and the University of Oviedo (OU). More recently, researchers from the Instituto Tecnológico de Aragon have joined the CMS collaboration (ITAINNOVA) and the National Microelectronics Center (CNM).

Carlos LacastaIFI researcher, and Celso Martinez, an IFCA researcher, are currently the Spanish representatives of ATLAS and CMS, respectively. This position is called National Contact Physicist and the person in charge acts as the contact between each collaboration and Spain. In the following lines, Lacasta and Martínez tell CPAN what the discovery of the Higgs boson meant and how this milestone was experienced in Spain.

a perennial news

“The discovery of the Higgs boson is news that will live for a long time: it will always be remembered that in July 2012 CERN showed us that a 125 GeV particle, very similar to the Higgs boson, had appeared in two different experiments. , ATLAS and CMS, and there were even two of the three people who thought of that boson almost 50 years earlier, Englert and Higgs,” explains Martínez. “For everyone it was very important, but for Teresa Rodrigo it was something very special, being President of the CMS Collaboration Board”, she adds, remembering her late colleague, also a researcher at the IFCA.

“The discovery of the Higgs boson is and has been very important for several reasons. The first and fundamental is that it is a type of particle that has never been seen in a detector until now. We also think it’s a fundamental particle, that is, it is not composed of others. We discovered something that, despite being “announced” a long time ago, is really new and we need to focus on knowing the properties of this new particle”, highlights Lacasta.

He continues: “The second reason is its own history. It was envisioned in 1964 to solve a problem that theoretical models had when it came to calculating the numerical values ​​of observables that we could measure in experiments. The introduction of the Higgs boson allowed these calculations to be made. Now, we had to find it, and with the knowledge and technology we had at the time, it was already clear that it would not be an easy task.”

It’s not an easy way

“After having searched -unsuccessfully- for the Higgs boson in the Large Electron Positron Collider (LEP), the predecessor of the LHC, we knew something had to appear at the LHC. And so it was: at the end of 2011 we saw that in the 125 GeV area there was ‘something’ to extract. The meetings where we shared analyzes related to the Higgs boson became more and more frequent, until in recent months they became daily. In the end, we knew that the Higgs boson was there… there was no other solution”, explains Martínez to CPAN.

Of the 50 years it took to “find the Higgs boson”, 30 were dedicated to the design and construction of the accelerator (the LHC) and detectors (ATLAS and CMS) that first spotted it.

Carlos Lacasta (IFIC)

For his part, Lacasta underlines the technological development necessary to find this elusive boson: “The search for the Higgs boson was not easy. In fact, it took 50 years to get it. The Higgs is a particle predicted by a theoretical model incapable of predicting the mass of this particle and therefore we had to start looking for it without knowing how much energy the accelerators must have to produce it. To give you an idea of technological challenges To those who had to face it, I will say that of the 50 years it took to “find the Higgs boson”, 30 were dedicated to the design and construction of the accelerator (the LHC) and the detectors (ATLAS and CMS) that they saw it for the first time. turn.”

A singular and inexplicable emotion

“During the discovery there was a lot of excitement, the result of a titanic international effort not only to develop the technologies that made it possible, but also to ‘manage’ the international collaborations themselves, whose number of participants has grown abruptly in recent decades. From Spain it was also very special. The Spanish research community played very important roles in some aspects of the design, detector construction and operationif in the generation of algorithms search and find among the millions of events produced those in which there could be a Higgs boson”, says Lacasta.

“The meetings, analyses, counter-analyses and the Higss boson candidates themselves, which were reviewed one by one, kept us very busy in 2011 and 2012, but we were very excited about it. Discovering a particle is something that can rarely happen in the life of an experimental particle physicist,” says Martínez. Lacasta shares his emotion: “You can’t always say you contributed to the discovery of a new particle, so you can imagine the emotion of the moment.”

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