Scientists celebrate the much-sought-after discovery of the odderon, a strange phenomenon that occurs only rarely when protons collide at high energies, such as inside particle accelerators. Although the odderon was first predicted to exist in the early 1970s, it was only recently that physicists finally gathered the data they needed from CERN’s Large Hadron Collider to confirm a true discovery.
The discovery contributes to physicists’ understanding of how all matter in the universe interacts at the lowest levels. Unlike the famous The Higgs boson, which was officially discovered in 2012, the odderon is not exactly a particle. Instead, it is the name of a compound made up of three gluons that switch between protons (or a proton and its antimatter twin, the antiproton) when they collide violently, but are not destroyed. Gluons are subatomic particles so named because they “stick” together other particles called quarks; quarks are the tiny things that make up larger particles like protons and neutrons that make up the atoms we all know and love.
Gluons are funny in that they don’t like being alone; they are almost always found together. When it is an even group of gluons (two, four, etc.), we call it pomeron. When the number of gluons in the group is odd (three, five, etc.), well, you guessed it: this is an odderon. Odderon, for mysterious reasons, is very rarely produced, and although evidence of it has emerged over the decades, the evidence has never been strong enough to say it certainly existed. But the generally accepted theory of quantum physics says odderoni should it exists, so scientists have continued to hunt them.
An international team of physicists announced earlier this month that their data had reached a level of statistical significance known as the “five sigmas”, a threshold that most scientists agree means you can be 99.999 +% sure that you really made a discovery. After all, it’s not like physicists can look inside their particle collision and see an odderon smiling back at them. Instead, they have to go through amazing amounts of recorded data when protons and antiprotons jump into the walls of their detectors.
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If you put all this data on CDs and stack them on top of each other, “you’ll travel more than the distance between Earth and the moon,” said Christophe Royon, a professor of physics and astronomy at the University of Kansas who is part of the team. behind the new research. “Collect a huge amount of data. And then you have to do an analysis to identify, among all this data, what is interesting to you. ”
If protons and antiprotons hit the detector after they hit each other, it tells researchers how the particles interacted when they collided. Physicists sort the records of millions and millions of these collisions, looking for enough suitable data points to be able to say with confidence that what they see could only be explained if the odderon exists. If they continue this research for years and never find evidence of the odderon, they should go back to the drawing board and come up with a new theory of how the universe works.
Fortunately, the researchers were able to gather their results from the particle collider before the covid-19 pandemic stopped their personal work, and then the data analysis could be done remotely. But they still haven’t managed to celebrate together.
“With the covid situation, it’s a little difficult – everyone works from home and so on,” Royon said in a video call. “But when we get back to normal, I think we deserve a party.”
The research involved a careful comparison of data sets: one created a decade ago in the now closed DØ experiment at Fermilab in Illinois and others conducted in 2015, 2019 and 2020 (before the pandemic crash) in the large hadron collector’s TOTEM experiment. The Fermilab experiment struck protons and antiprotons, while LHC’s work looked at protons striking protons. By comparing the data from these two different colliders, they were able to be so sure about the existence of the odderon.
Although the team, which involved researchers from countries around the world, suspected they had something big last year, they did not want to rush an announcement. They asked independent researchers in the field to check their work for potential biases or problems before making them public. The article is now published as a prepress by CERN and Fermilab and was sent to the journal Physical Review Letters.
“Odderon is a solid prediction of the theory of strong interactions, made almost half a century ago,” said physicist Yuri Kovchegov of Ohio State University, who was not involved in the new paper. “At the same time, it has been avoiding experimental detection for decades. The new result DØ and TOTEM, if maintained, is likely to indicate that the odderon has finally been found. ”
Kovchegov said in an e-mail that the work “appears to be the first solid experimental evidence of the odderon’s existence,” although he would like to see more experiments to confirm the finding. He said the future Electron-Ion Collider, a major new experiment to be built in New York and to be opened in the early 2030s, may be able to answer the ongoing questions about odderon.
Royon agrees that the work of studying the odderon is far from complete. “It’s not something we close and say we’re happy, done, done,” he said. “In physics, when you find something new, it’s usually a door that opens up completely new areas.”