GENEVA (dpa) – After three good years of maintenance and improvement, the world’s largest research machine has started again: the Cern Particle Accelerator in Geneva.
On Friday, the first two proton beams will be chased in opposite directions through the 27-kilometre underground ring. It takes six to eight weeks for the device to reach speed. Only then can proton collisions occur again, which should reveal knowledge of the basic laws of the universe.
Very nervous until the last minute
Preparations have been going on around the clock for a few weeks. Cern’s control rooms are tense until the last minute. “It’s like launching a missile,” says Joachim Mnich, director of research at Germany’s CERN, of the dpa news agency. “It often has to be canceled minutes before the start due to a problem. But we hope everything goes smoothly.”
In this case, the proton beam, which was initiated by the push of a button and rotated through the loop, could be seen on computer screens after a short time. “Before that, the proton beam usually had to be shifted millimeter by millimeter using electronic signals, and sometimes had to be directed through the eyes of a needle, which doesn’t always work right away,” says Mnich.
Simulation of the emergence of the universe
A particle accelerator is used to simulate the time when the universe originated about 14 billion years ago. Researchers observe decay processes during collisions and gain insight into the smallest components of matter, the elementary particles. Among other things, the Higgs boson, which was theoretically described 40 years ago, was first discovered at CERN in 2012. It contributes to the fact that elementary particles have mass.
During shutdown, the performance of the accelerator and the detectors connected to it has been significantly increased. That means more collisions are possible, about 1,000,000,000,000,000 per year, one quadrillion, says Mnich. However, only one in 100,000 collisions reveal processes worthy of careful analysis. Although data is stored within milliseconds, evaluation often takes years.
Unknown forces of nature and newly discovered particles?
Such was the case at the American research center for particle physics Fermilab, which came up with a sensation at the beginning of April: physicists recalculated the W boson from data more than ten years old, which conveys one of the four fundamental forces that determine the behavior of matter in the universe. The researchers determined with high accuracy that it is heavier than the Standard Model of particle physics expects. This model describes twelve substances and their interactions.
The W boson was discovered at CERN in 1983. There, Minich hopes, the Americans’ findings can be confirmed or refuted in the next few years. “If the result is correct, this could be an indication of an unknown force in nature, or an indication of additional particles that we haven’t identified yet,” Mnich says.
An anomaly deviating from the Standard Model of particle physics was discovered at CERN last year in an entirely different context. Beauty quarks did not decay into muons and electrons in equal parts, as expected. With greater amounts of data, physicists now hope to gain new insights that could raise more questions about the validity of the Standard Model.
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