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It’s been a big few weeks for physics. First, in what is probably the announcement of the year, we managed to see the birth of a black hole in real time. And now, on the completely other end of the scale, we’re starting to get to grips with how the tiniest possible bits of matter interact.

Granted, it might not mean much to you, but a group of physicists has announced a groundbreaking discovery about subatomic particles, something the LHC has been searching for, and they’re pretty excited.


The team behind a new paper has announced the first unambiguous evidence for a special theory of how matter interacts, and it means a theory that’s been around since the 1950s makes a bit more sense.

“It is not as mind-boggling as neutron star merger, but we have also discovered something,” says Juan Rojo, from the Free University of Amsterdam, and co-author of the paper outlining the discovery entitled Evidence for ‘new physics’ within QCD.

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Quantum chromodynamics (QCD) is the theory used to explain the strong interaction between quarks and gluons, two of the fundamental particles described by the standard model. QCD is essentially at the root of any interaction that a particle accelerator such as the LHC is looking for.

Physicists use theory to predict how particles like this will interact, but at very low energies this theory breaks down and doesn’t provide a good enough prediction. For 25 years, another theory has been suggested for these low-energy interactions, but nobody has managed to find evidence to support the new theory, called BFKL dynamics. Until now.


As the value of x gets smaller and smaller (towards the right of the graph) the results showed, the QCD description of what happens (in green) stops predicting the right results. But, if BFKL dynamics are included (shown in blue) the description fits the data. Richard D. Ball et al

The team used data from the HERA particle accelerator, which operated in Hamburg from 1992 to 2007. They studied interactions involving protons, in which the energy a quark carries compared to the total energy of the proton is given the number ‘x’. So if x is 0.1 this means the quark carries a tenth of the energy of the proton.

As the value of x gets smaller and smaller, the results showed, the QCD description of what happens stops predicting the right results. But, if BFKL dynamics are included, the description fits the data.


“We have shown another face of QCD,” says Rojo. “It is the onset of a new dynamical regime that had been searched for 25 years without success.”

Rojo has personally been working on this problem for ten years, since he started in his first postdoctoral position in a lab. “It has taken a lot of time, but the results are worth it,” he says.

And he feels really excited about the results. “I always insist that new physics can also be discovered within known theories,” he says. “Sure, it is not a gravitational wave, but it’s pretty cool anyway.”