happy birthday higgs boson

Ten years ago, July 4, 2012, a crowded hall CERN – on the Franco-Swiss border – witnessed how his scientific collaboration ATLAS D sms provides convincing evidence for the discovery Higgs boson. “We have reached an important milestone in our understanding of nature,” said the then director general of CERN. Rolf Hoyer.

The news spread around the world, and for good reason: the existence of a mechanism predicted by theoretical physicists in the 1960s, which helps to better explain the Universe around us, has been confirmed.

To celebrate this tenth anniversary of the Higgs boson and spread its meaning, many events have been organized in different countries. One of them was a conference they held this month at the National Museum of Science and Technology (MANZITE) scientists Maria Zepeda Ermida D Jesus Puerta Pelayotwo physicists from the Center for Energy, Environmental and Technological Research (St.CIEMAT) working on an experiment with CMS.

“What are the fundamental building blocks of matter, our world?” they asked themselves a question raised since ancient times, which today helps to solve particle physics. He was born in the 20th century thanks to the revolutionary contribution relativity (energy and mass are two sides of the same phenomenon, as indicated by the famous equation E=mc^two) and quantum mechanics (which speaks of probability, uncertainty, of being a wave and a particle at the same time).

Standard Model and elementary particles

In this regard, it was proposed standard model, one of the most accurate theories ever built, the result of theory and experiment that have worked hand in hand for over a century and have a very powerful mathematical foundation. “This is our current explanation elementary particles The universe and its interconnections: which begins at the end of the 19th century with the discovery of the electron, continues with the discovery of other particles (photon, muon, quarks of various types …) and currently ends with the discovery of the Higgs boson in 2012,” explains Cepeda.

“Moreover,” he adds, “these building blocks that make up the cosmos are connected with four forces nature: gravity, electromagnetism (light), strong nuclear force (it holds neutrons and protons together in the nucleus without repulsing the latter from each other) and weak (responsible for the radioactive decay of particles). But at the center of it all Higgs boson, a special particle without charge and spin. If we didn’t find this central element, we would have to disassemble the entire model and start over.”

The existence of this boson was raised in 1964 Belgian scientists Robert Braut D François Engler and the British Peter Higgs in several papers, which dealt with broken symmetries, those that are preserved in theoretical equations, but can be violated in real physical systems.

To solve some dilemmas about the mass of carriers of the weak interaction – the W and Z bosons – the so-called Braut-Englert-Higgs mechanism (or simply the Higgs) with two main components: an entirely new quantum field that gives mass to these and other particles: Higgs fieldand one spontaneous symmetry breaking.

Interaction with the Higgs field gives particles mass

When the universe was born, it was filled with the Higgs field in an unstable but symmetrical state. A fraction of a second after the Big Bang, this field acquired a stable configuration, but broke the original symmetry. “At this point, the electromagnetic force (light) and the weak nuclear force (radioactivity) are separated by the Higgs mechanism, that is, the interaction with the Higgs field, which gives the particles mass,” Cepeda explains.

Physics reminds us that particles don’t have their own mass, they get it by interacting with this field. The stronger the force, the heavier the particle, like a quark, will eventually be. However, electrons barely interact, and photons don’t interact at all, so they have no mass.

The real Higgs boson wave or oscillation in this fieldsomething hard to imagine. “At some point, you have to forget that all these things can be visualized in terms of probability, duality of entities, interactions that are not collisions, etc.,” Puerta points out, although this is sometimes simplified in illustrations and video.

In 2013, Peter Higgs and François Engler (Braut died in 2011) received the Nobel Prize in Physics “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of the mass of subatomic particles and confirmed by the discovery of the predicted particle using the ATLAS and CMS experiments in Large Hadron Collider (LHC) CERN.

The door remembers CERN, named after its French acronym (Conseil Européen pour le Recherche Nucléaire), is the only place in the world where the Higgs boson can be studied and measured. This center was founded in 1954, it is now the “home” of almost half of all physicists and particle physicists, it is headed by one of them (Fabiola Gianotti), and Spain contributes 8% of its budget in addition to an active research community.

Concerning TANKlargest particle accelerator in existence, ring 27 kilometers circumferentially located 100 meters underground near Geneva. It is designed to achieve maximum energy 14 teraelectronvolt (TeV), which means work at speeds close to the speed of light. Inside, proton beams collide every 25 nanoseconds at four points where the same number of detectors and experiments are located: CMS, ATLAS, LHCb and ALICE

Higgs ‘visible’ due to its decay

“What we are really seeing in these detectors are the products resulting from Decay of the Higgs boson, and not to the boson itself, a highly unstable wave or particle,” explains Puerta. This boson was not discovered because it would be found somewhere: it had to be created as a result of collisions in order to then “see” how it decayed.

“The July 4th message didn’t mean we took a ‘photo’ of him and said look, we found him!” – adds Cepeda, – “seeing only one, we cannot know what happened, because there are many different events.” which decay in the same way, leaving the same trace. Also, we only control the energy of the protons colliding, but when they collide, we don’t know what will come out, it’s probabilistic. We know that some particles will be produced many times, for example b-hadrons; others are not as strong as the W and Z bosons, and the Higgs boson is very, very rare: it’s like finding needle in a haystack”

In fact, it appears in only one of the LHC’s billions of collisions, and careful verification is required to confirm that this is indeed the case. statistical analysis, using huge amounts of data and selecting only collisions of interest. Then, through programmingthe key parameters of the resulting particles are calculated, such as their mass, and the final graphs are built with all the photos or events of the target event (for example, the decay of the Higgs boson into two Z-bosons, which, in turn, into four muons), a task that can take some years.

In the decade since its discovery, various decays of the Higgs boson and the strength with which it interacts with other particles have been measured at CERN. For example, in 2016, interaction with tau leptons was discovered, and in 2018, with up and down quarks.

At the end of the same year, the LHC was stopped for maintenance and upgrades. In April 2022, it again began preparations for the third data collection period, or Launch 3which officially kicks off on July 5, just one day after the 10th anniversary celebration.

In search of new physics

“During Run 3, the amount of data will be more than double what we have to date, and thanks to this we will be able to improve the statistics of our results, especially in terms of the accuracy of the standard model, and go beyond the physics we know,” Puerta emphasizes.

During this third period of data collection (Run 3), the number of data will be more than doubled, which will improve the statistics of our results, especially in precision measurements of the Standard Model and the search for new physics.

Jesus Puerta Pelayo (CIEMAT/CMS)

“The discovery of the Higgs boson was the starting point for studying its properties and what it tells us about the model we know, which is very good and accurate, but does not explain everything,” adds Cepeda.many questions remain: Is the Higgs boson really an elementary particle, how does it get along with the rest, does it really follow all the rules of the standard model, or can it decay “illegally”? A good understanding of the Higgs boson is incredibly important for understanding not only the particle itself, but also its significance in the universe, understanding how it all works.”

Some answers may come after the launch of LHC 3, which for the first time will operate at a record energy of 13.6 TeV, close to the maximum value of 14 TeV, but particle physicists are already looking further, to an even more powerful machine. which is planned to be built next door: Future Circular Collider (FCC)A 100-kilometer ring that will produce collisions up to 100 TeV and that could start operating at the end of 2050. Time will tell if the desired new physics is found much sooner.