In Switzerland, 100 meters underground, mysterious forces are at work: scientists at the European Institute for Nuclear Research (CERN) say their results deviate from basic theories of physics.
For 14 years, scientists have been colliding with particles at the LHC, a 27-kilometre accelerator, after which they studied energy-rich products. Experiments on a large scale confirm what we know about the formation of the universe and about the natural forces that drive everything. But the past five years have been Results In one of the reagents, LHCb, it is very surprising.
The detector measured a strange particle that does not behave as it should when it decays into particles of lower energy. So there must be an unknown force influencing the process – perhaps a new force of nature in addition to the four we already know.
The new force of nature will not only be the discovery of the century, but will also open up new possibilities to explore the deepest mysteries of the universe. Perhaps we will find out why matter exists, what holds galaxies together, and whether there are subtle dimensions.
1000 physicists are watching
Scientists around the world are following the collisions at the LHCb detector. About 1,000 physicists are sitting at their computers analyzing the wealth of data from experiments – knowing that they can write the history of science.
An unknown force of nature will challenge the so-called Standard Model of physics, which includes everything we know about matter and forces in the universe.
This model now includes four natural forces: the gravitational force, the electromagnetic force, the weak nuclear force, and the strong nuclear force.
The four forces of nature vary greatly in extent and strength. Although most of us have gravity Knowing the best of our daily lives, they are much weaker than the other forces.
Compared to the second weakest force, the weak nuclear force, gravity is weaker by a quintillion (1 with 30 zeros) times. While the other three forces largely determine how particles in atoms interact, the effect of gravity is too small to measure.
On the other hand, gravity acts over very large distances. While the nuclear forces have an effect only at the atomic level, the range of gravitational force and electromagnetic force is essentially infinite.
If there is a fifth force of nature, we don’t know how far it will go, but LHCb experiments indicate that it plays at least a role in atomic nuclei.
Unstable particles break the law
The Standard Model divides all particles into two types: force particles, which carry the forces of nature, and matter particles, which make up all matter in the universe. The latter include, for example, electrons and the so-called quarks, which are the basic building blocks of the nucleus of an atom.
Quarks come in many different types. Protons and neutrons are made up of the lightest types, which are called up and down quarks.
The Standard Model also includes four heavier quarks, called strange, charm, down and up quarks. Like up and down quarks, they can fuse into larger particles, which we call hadrons.
But when this happens, they are very unstable. For example, a hadron containing a bottom quark rapidly decays into a lighter type of hadron. The down quark is transformed into a lighter quark and at the same time an electron or the so-called muon – the electron’s heavier cousin – is released.
And those by-products of decomposition are measurable using LHCb†
According to the Standard Model, there must be something called universality between the two types of decay. This means that the probability of releasing an electron is the same as the probability of releasing a muon.
So the detector must register an equal number of electrons and muons from the decay, but this does not happen. After more than five years of experiments in which decay has been measured hundreds of billions of times, there is still a difference.
Of the 100 times measured, 54 times there is an electron as a byproduct—and only 46 times a muon. And this is a blow to the Standard Model, which has been tested with unprecedented precision in thousands of other experiments. If the universality of the model declines, then unknown physical phenomena must be involved.
Physicists must make sure
Of course, when physicists challenge a tried-and-true theory such as the Standard Model, they must be absolutely certain of their case. After all, despite all the data, the difference in electrons and muons could be a statistical coincidence.
So LHCb scientists are very cautious and spend a lot of time calculating the probability that the results are not just a coincidence.
To do this, they use a special scale where the Greek letter sigma symbolizes the probability of chance. At 1 sigma, there is about a 16 percent chance that the observations are due to chance.
Physicists need 5 sigma before they dare to report a new discovery. This means that the chance of chance should be only 1 in 3.5 million.
With the latest results from the LHCb, the certainty is more than 3 sigma, which means that there is a 0.1 percent chance that the measured difference between electrons and muons is due to chance. In other words, the results are 99.9% certain.
If measurements continue to show the same difference in the coming years and researchers reach their goal of 5 sigma, then theoretical physicists will offer all kinds of possible explanations.
Most theories propose a new type of force of nature, similar to the four known theories. If we follow the logic of the Standard Model, it will operate through a force-carrying particle and, like other forces, will be transmitted by photons, gluons, or W and Z particles.
We hope the new forces of nature will contribute to solving the greatest mysteries of the universe.
If a force-carrying particle of the new force of nature had a mass like W and Z particles, it could solve one of astrophysics’ greatest mysteries: dark matter.
Visible matter makes up only one fifth of the mass of the universe. The rest is something we can’t see. We only know that it exists because we can notice the effects of its gravity.
A new force from nature could act as a mediator between the particles in dark matter and the particles we know from the Standard Model. And with the help of nature’s new forces, we may even be able to create dark matter in the lab.
Furthermore, an unknown force can open the doors to invisible dimensions that may exist in the universe. Here we may be able to answer the question of why gravity is weak – perhaps only disappearing into unknown dimensions.
Japan and the United States are in the lead
Scientists at the LHCb are now leading the search for the unknown force of nature. But it could be bypassed in the coming years, because the CERN accelerator will then be closed for promotion.
In the Belle II experiment in Japan, physicists have also begun to measure the decay of hadrons with down quarks, and it is doubtful whether they will detect the same difference as the researchers detected in the LHCb.
At the Fermilab accelerator in the US, physicists are chasing an unknown force from nature in a different way.
The experiment is looking at muons, which behave like magnetic spinning tops. When muons are exposed to a magnetic field, their spin axis changes, but only 0.1 percent more than theory predicts. According to the researchers, the deviation may be due to an unknown force of nature.
The next decade will show which team reaches 5 sigma first. In 2028, the upgrades at CERN will be ready and European scientists can start a fast sprint.
By then, they would be able to collect results at least ten times faster than before. This way they get the best tool in searching for evidence of the unknown force of nature.
