For almost 50 years, physicists have been looking for evidence of the “God particle” Higgs boson. In 2012 they were able to announce the discovery. Is that the end of the particle accelerator in Geneva?

In Geneva, physicists are anxiously waiting for the particle accelerator (LHC) to be up and running again after a good three years of maintenance. When the necessary collision energy is reached around July 5, protons will again be injected into the gigantic subterranean ring in opposite directions and smashed into each other at almost the speed of light.

Rare production and decay processes can be observed during the collisions, which caused a world sensation exactly ten years ago: the European Organization for Nuclear Research (CERN) in Geneva announced on July 4, 2012 that the Higgs boson had been found. The particle confirms the existence of the so-called Higgs field, which gives elementary particles their mass.

While the experts in Geneva are hoping for lots of new findings for particle physics from the new, third test track, colleagues from the USA are coming down with a cold shower: from the “nightmare of not being able to find anything anymore”, writes the specialist magazine “Science”. Detection of the Higgs boson was one of the main reasons why the particle accelerator was built in Geneva. Is his mission accomplished? What if there was nothing left to discover?

Observe two particles at the same time

Is there envy on the other side of the Atlantic, where there is also a particle accelerator, but the Higgs boson was not discovered? “You’re standing in front of a desert (at Cern) and you don’t know how big it is,” the magazine quoted University of Minnesota physicist Marvin Marshak as saying.

The CERN particle physicist Michael Dührssen-Debling sees it differently. “The Higgs boson fits the theory beautifully, but since it is so different from everything else we know, there is still no fundamental understanding of why it is the way it is,” says the Darmstadt native of the German Press Agency . It would be exciting to find out how strongly it couples to the known matter particles, or what interaction two Higgs bosons would have with each other. Because observing two Higgs bosons at the same time is extremely rare, even more proton collisions would have to be generated.

Dührssen-Debling was there ten years ago when the data that experts had been waiting for for almost 50 years was finally delivered at Cern. Physicists, including Peter Higgs, had theoretically predicted the Higgs boson back in the 1960s (the 2013 Nobel Prize in Physics was awarded for this), but proof was lacking for a long time. So how exciting was the discovery back then at CERN?

Discovery in the bath

“There wasn’t a Eureka moment back then,” reports Dührssen-Debling of the German Press Agency. Eureka, ancient Greek for “I found it”, is said to have been called out by Archimedes more than 2000 years ago when he suddenly made a groundbreaking discovery in the bathtub. Particle physicists in Geneva had suspected for months that they were on the trail of a sensation. However, the billions of proton collisions per second generate vast amounts of data that first have to be evaluated on the computer.

“You first saw some promising signals in the data, then some that turned out to be statistical fluctuations,” says Dührssen-Debling about the exciting months leading up to July 2012. “When we then saw a clear signal” – described here Dührssen-Debling made a huge curve with his hand – “of course there was a lot of excitement”. But physicists need to know very well. The probability that it is a misinterpretation is said to be less than 1 in 3.5 million. As they approached that number, they made the world sensation public on July 4, 2012.

Particle physicists may turn up their noses, but outside of the scientific community the Higgs boson is often referred to as the “God particle”. The name comes from the fact that without the Higgs field, many particles would not have a fundamental mass, so they would lack fundamental properties and nothing in the universe would be as it is. The physicist David Miller found a vivid image for this: There are many people at a party, they symbolize the Higgs field. When a celebrity walks in to the bar, they make the first few steps with ease, but then more people crowd around them and their progress slows – like elementary particles gaining mass in a Higgs field.

Getting to the bottom is worth it

Why do particle physicists still need to know things better? “Basic research,” says Dührssen-Debling. It’s always worth it, even if it’s often hard to predict at the beginning what could develop from it. The Cern refers to devices and procedures that were developed there and are used today in medicine, especially in cancer therapy and tumor control. Or the World Wide Web, the starting point of the digital revolution, for which Cern computer specialist Tim Berners-Lee created the basis in 1990.

Apart from further research into the Higgs boson, other experiments are being carried out at CERN. The discovery of new particles is not excluded. “There are theories that predict new particles like dime a dozen,” says Dührssen-Debling. Only experiments could support or refute these theories. According to him, it would be just as interesting to find properties in known particles that contradict expectations. There have already been initial indications of so-called beauty quarks. If confirmed, it would indicate an unknown force of nature and would be a new sensation.