Ten years after the discovery of the Higgs boson

Reconstruction of a proton collision recorded at the Large Hadron Collider. / cern

Science | Physical

After almost fifty years of searching, the Large Hadron Collider managed to confirm its existence, key to understanding the visible matter of the universe

Elena Martin Lopez

Exactly ten years ago, on July 4, 2012, the equation written by Robert Brout, François Englert and Peter Higgs in 1964, which predicted the existence of the particle known as the Higgs boson, and which earned the latter two the Prize Nobel Prize for Physics in 1965 (Brout died before), went from being a mere formula on a blackboard to one more milestone in the history of science. The event was possible, after five decades of research, thanks to the work carried out at the Large Hadron Collider (LHC), through the ATLAS and CMS particle detectors of the European Organization for Nuclear Research (CERN), and it ushered in a new era in the study and understanding of the universe.

“The Higgs boson has a relevance for physics comparable to that of the discovery of DNA in biology, or the evidence of atomic and molecular structure in chemistry. From the technological point of view, it represents a milestone comparable to the arrival of the human being on the Moon, but its scientific repercussions are much more important”, says Antonio Pich, director of the CPAN (National Center for Particle, Astroparticle and Nuclear Physics). , which includes all the Spanish groups that participated in the discovery of the Higgs boson.

The particle discovered by the LHC coincided with the one described by the Standard Model, which is equivalent to physics what the periodic table is to chemistry, that is, the best current theory to describe the elementary pieces that make up the universe. In it are all the basic particles of which matter is made. That is, the smallest components of everything that exists, called fundamental particles.

These are the first to appear after the birth of the universe and are divided into two types: fermions and bosons. Fermions are those that make up matter, such as electrons, muons, taus and quarks, which give rise to such basic components of our world as stars, a chair, a beer or this newspaper. The bosons, on the other hand, are what make the particles interact. Some examples of bosons are photons, gluons, W and Z bosons or the Higgs boson.

A step forward

The great importance of the latter within the Standard Model lies in the fact that it is the element that helps all particles have mass. The 2012 discovery allowed this hypothesis to be confirmed.

This has meant a great step forward in the study of the universe and the most up-to-date results of the properties of this elementary particle have been presented this Monday in two independent articles published in Nature. According to the Higgs theory, there is a quantum field (the so-called Higgs field) that, although invisible, extends throughout the universe. If we compare it with the sea, the Higgs field would be the entire water surface and the Higgs bosons would be equivalent to the H2O molecules that make it up. When a particle crosses this quantum field, a resistance is produced, and this is what determines its mass.

Newly published experiments have demonstrated many of the Standard Model's predictions, such as that the Higgs boson has no quantum spin (one of two intrinsic properties of particles, along with electric charge), or that fermions get their mass passing through the Higgs field. On the other hand, they have provided new knowledge by obtaining the mass of the Higgs boson itself, about 125,000 million electron volts (GeV), which is nothing less than a fundamental constant of the universe, not predicted by the Standard Model.

They have also observed many rare particle processes, made increasingly precise measurements of Standard Model phenomena, and blazed trails in the search for new particles beyond those predicted by the Standard Model, including particles that can form dark matter, which represents most of the mass of the universe.

Questions without answer

However, ten years later, there also remain many unanswered questions about this finding. After all, the knowledge we have so far of the Higgs boson only refers to ordinary matter, which represents only 5% of the Universe, but the Standard Model does not clarify anything about the remaining 95%, relative to matter dark, the one that does not interact with the electromagnetic field and, therefore, we cannot see, even though we know it exists; and dark energy, responsible for the expansion of the Universe. The properties of both remain a mystery to science.

This means that there is still a lot of room to reveal new and exotic phenomena, such as the possible generation of dark matter from the disintegration of the Higgs boson, or the existence of more than one type of Higgs boson, for example. While these answers were expected years ago, CERN physicists are keen to resolve the remaining questions and bring the LHC to its full potential.

Run 3 is proof of that. After three years of updating and maintenance work, this Tuesday the LHC begins its third period of activity, which in principle will last 4 years. Among its advances is its renewed ability to record an unprecedented number and power of collisions, reaching a record energy of 13.6 billion electron volts, which will increase the accuracy of the studies.

“The LHC has not yet said its last word and new revolutionary discoveries may be waiting. However, despite its potential, the LHC has its limitations. In order to continue penetrating the mysteries of the universe, new accelerators, capable of achieving unprecedented precision and energy, are being designed", says Aurelio Juste Rozas, ICREA researcher at the Institute of High Energy Physics (IFAE), who studies proton collisions -proton in the ATLAS experiment at the LHC. In other words, everything indicates that the Standard Model is not the definitive paradigm for understanding the universe.

If we find the answers we seek, in the next four years we will gain a whole new perspective on the universe, from its subatomic scale to its entirety (how it came to be what it is and what its future holds). "A new and exciting stage of scientific research is opening that we hope will bring us great surprises," says Pich. "Not giving up is the key," adds Javier Fernández Menéndez, full professor at the University of Oviedo, researcher of the CMS experiment since 2003 and, in recent years, responsible for Quality Control and Data Monitoring at CMS, "other recent discoveries Like gravitational waves, it took almost a century from when Einstein's theory of General Relativity predicted them to the confirmation of their existence."

The controversial 'God particle'

The Higgs boson has also been dubbed 'the God particle', despite physicists disagreeing on that name. The nickname originated from a popular science book on elementary particles that Leon Lederman, Nobel Prize in Physics, published in 1993.

Lederman originally titled his book 'The Goddamn Particle: if universe is the answer, what's the question?' ('The damn particle: if the universe is the answer, what is the question?', in English), given the difficulty of discovering the Higgs boson (it took 50 years). However, the editors thought it might be offensive and considered "The God particle" to be more attractive and commercial. So it was, the book was successful and that formula to refer to the Higgs boson became popular.

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