July 4, 2022 will mark ten years since physicists at CERN announced the discovery of the Higgs boson. After a search of nearly fifty years, the missing elementary particle from the Standard Model was finally found.

Peter Higgs already predicted the existence of this subatomic particle, which is responsible for the mass of atoms, in 1964. But it’s not until thirty years later that the Large Electron-Positron Collider (LEP) really begins to search for the mysterious particle.

Mass = Cash register

Together with other accelerators, the LEP is making more and more clear about the possible mass of the Higgs boson, but still no tangible evidence is found. Until 2008, the Large Hadron Collider (LHC) at the CERN particle lab in Geneva, Switzerland, begins its first series of runs.

The underground, annular particle accelerator has a circumference of 27 kilometers, cost billions of euros to build and its main mission is to demonstrate the Higgs boson. Never before have subatomic particles collided with each other as a result of human action.

No end of the world, but champagne

It will take another four years, but then the champagne can open. The particle is picked up after a spectacular collision of protons, which travel almost as fast as light. Shortly thereafter, the Higgs boson disintegrates again. But enough evidence was found in 2012 to rule out other explanations for the data. The chance that there is a fluke is less than 1 in 3.5 million.

Nikhef

Scientists and technicians from the National Institute for Subatomic Physics Nikhef in Amsterdam played an important role in the successful search for the Higgs boson and subsequent research.

At the time, Nikhef director and professor at the University of Amsterdam Stan Bentvelsen was leader of the Dutch Higgs research with the ATLAS detector at CERN. (Conseil Européen pour la Recherche Nucleaire† He looks back on the press conference with pride: “Ten years ago it was very exciting. With the ATLAS detector, we had enough evidence for the existence of the Higgs boson, which had been searched for so long. On that fourth of July in 2012, everything came together. Our results and those of the other experiment at CERN, the CMS detector. They saw the same. This left no room for doubt: the Higgs boson had been discovered.”

Graphical representation of the Higgs boson. © 2015 CERN / Dominguez, Daniel: CERN

Goosebumps

“I was in Amsterdam that day at Nikhef, where we followed the announcements on big screens with colleagues and a lot of press. That was goosebumps. A holiday in all respects,” Bentvelsen recalls.

The Dutch professor explains which important insights the discovery of the Higgs boson has yielded: “The existence of the Higgs boson was mainly proof that our particle theory is already very good. The Higgs boson is theoretically necessary to explain how particles get their mass.”

The search continues

After that it didn’t stop. “Over the past ten years we have done two things with the accelerator and the detectors at CERN,” says Bentvelsen about the time after the discovery. “First of all, we were looking for even more unexpected particles, that search is always ongoing. But we also checked very precisely whether the Higgs particle we found really works as we think.”

The conclusion? “So far the answer has been ‘yes’: the Higgs boson actually does exactly what we expect. That doesn’t sound very exciting, but it’s important, because we have all kinds of ideas about how the Higgs boson played a role in, for example, the Big Bang. If we know the Higgs well, we also better understand how the universe came into being,” said the physicist.

More intense than ever

The LHC has been active for several months after a three-year maintenance break. The energy released by the proton collisions is greater than ever at 6.8 teraelectron volts (TeV). The wait has not been in vain. The third run has started. “On July 5, 2022, the Large Hadron Collider will begin a new measurement period. At full power, with the clearest beams we can make. The Swiss circular accelerator chases protons to enormous energy and the speed of light. When they collide, Higgs particles are formed, among other things. So much so that we can study them better than ever,” says Bentvelsen.

black matter
But the LHC does more. “There are still all kinds of links with other particles that we don’t know well. In addition, the experiments hunt for deviations in certain processes, for which indications have occasionally surfaced. There is always the possibility of unknown new particles,” says Bentvelsen.

He says there are still some great challenges ahead. “There are still many unanswered questions in our field. About four-fifths of all matter in the universe cannot be seen. What is that dark matter? We only know a small part of the matter that exists.”

Asked about the expectations for the future, the scientist is very enthusiastic: “With the accelerator and detectors such as ATLAS at CERN, we can go on for years to come, looking for new particles, for more precision, for deviations from what we think we know.”

Exciting Global Quest

But you don’t necessarily have to go to Switzerland for new insights into the elementary particles. “Interestingly, the particle world and the universe can also be looked at in all sorts of other ways. From cosmic ray antennas in the desert of Argentina to neutrino detectors in the depths of the Mediterranean and gravitational wave antennas in Italy,” says the professor. “We may soon be doing measurements in Limburg. We can still learn a lot about the universe and its building blocks if we analyze this data and knowledge. These are exciting times.”