Dark matter makes up 27 per cent of the mass of the universe and is thought to hold galaxies together. Photo / Bryan Goff, Unsplash
Dark matter makes up 27 per cent of the mass of the universe and is thought to hold galaxies together. Photo / Bryan Goff, Unsplash
The key to understanding how the universe works may have been discovered by scientists at the Large Hadron Collider, in a breakthrough hailed as the most exciting in 20 years.
Particle physicists have seen signs that a mystery particle or force is interacting with other particles in a manner never witnessed before.
It may explain some of the deepest puzzles in modern physics, such as what dark matter is made from, or why there is an imbalance of matter and antimatter in the universe.
Currently, scientists understand the universe using the Standard Model, a theory which describes all the known fundamental particles and the forces that they interact with.
It sets out the workings of the building blocks of nature: quarks, leptons, force-carrier particles, and the Higgs boson.
But the Standard Model breaks down when it comes to explaining crucial issues such as gravity or why the expansion of the universe is accelerating.
It also cannot account for dark matter, an invisible substance which makes up 27 per cent of the mass of the universe and is thought to hold galaxies together.
The Large Hadron Collider at CERN near Geneva, Switzerland. Photo / CERN
To find out what is going on, scientists at the Large Hadron Collider created particles known as beauty quarks which existed soon after the Big Bang but which decay quickly into electrons and muons, and now no longer exist in nature.
But they discovered they are not behaving in the way they expected. Under the Standard Model, beauty quarks should decay into particles called K+mesons, which have either two muons or two electrons.
Scientists found for every 100 mesons with electrons, there were just 85 with muons, something that cannot happen under the Standard Model.
It suggests never-before-seen particles or forces are tipping the scales away from muons.
Dr Mitesh Patel, from the Department of Physics at Imperial College, and one of the leading physicists behind the measurement, said: "We were actually shaking when we first looked at the results, we were that excited. Our hearts did beat a bit faster.
"It's too early to say if this genuinely is a deviation from the Standard Model but the potential implications are such that these results are the most exciting thing I've done in 20 years in the field. It has been a long journey to get here."
The LHC is the world's largest and most powerful particle collider – it accelerates subatomic particles to almost the speed of light, before smashing them into each other.
These collisions produce a burst of new particles, which physicists then record and study in order to better understand the foundations of nature.
In the Standard Model, electrons and their heavier cousins, muons, are treated identically, so beauty quarks should decay into muons just as often as they do to electrons. The new result suggests that this is not happening.
Dr Paula Alvarez Cartelle, of the University of Cambridge, one of the team leaders, said: "This new result offers tantalising hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles.
"The more data we have, the stronger this result has become. This measurement is the most significant in a series of results from the past decade that all seem to line up – and could all point towards a common explanation.
"The results have not changed, but their uncertainties have shrunk, increasing our ability to see possible differences with the Standard Model."
'Excited but cautious'
Scientists say the latest result offers for the first evidence that there could be something wrong with our current understanding of particle physics.
But there are still concerns it may be a fluke, and Bristol University particle physics group is currently trying to confirm the results.
Dr Konstantinos Petridis of the University of Bristol's School of Physics, one of the physicists behind the measurement, said: "This has been a seven-year saga. Over this period, we have been seeing clues of a new unexplained process at work, but the effects were too subtle to draw any conclusions.
"We are very excited about this result but remain cautious as well.
"The discovery of a new force in nature is the holy grail of particle physics. Our current understanding of the constituents of the universe falls remarkably short – we do not know what 95 per cent of the Universe is made of or why there is such a large imbalance between matter and anti-matter."
