The mass of this particle can violate known physical laws

THE SCIENCE. This may well become a major physical discovery that changes all the laws known to date. Physicists have found that one of the 17 elementary particles known to physics, the W boson, is 0.1% heavier than expected. Reported in the journal The science On April 7, this new measurement came from the US Fermilab Particle Accelerator (or CDF), which specializes in high-energy particle physics.

While this difference in mass may seem small, it may nevertheless herald a revolution in fundamental physics. “It would be a complete shift in how we see the world,” the researcher says. Quanta-magazine, Sven Heinemeier, physicist at the Institute for Theoretical Physics in Madrid. Indeed, this will entail the first major reworking of the laws of quantum physics in half a century.

Change Model

Specifically, if the mass of this particle is actually heavier than previously thought, this changes all physical laws. Imagine playing Tetris. Each particle is a part, forming a perfect whole. Only if one of the parts gets bigger does the whole thing stop working. Therefore, it is necessary to rebuild the whole by changing the shape of the parts or even adding new ones in order to find the exact balance.

Thus, if the mass of the W boson is slightly larger, this means that the current physical laws no longer apply and that a new model must be found to explain the functioning of the universe, from stars to everyday objects.

Indeed, everything around us is made up of subatomic particles of matter. They are divided into two families: quarks (like neutrons and protons, the elements that form the nuclei of atoms) and leptons (like electrons). In total, 12 elementary particles are listed today, forming the category of fermions.

These particles of matter interact with each other. To do this, particles of a different type must intervene: interaction particles. Called bosons, there are four of them, not counting the Higgs boson (or god particle). These are interaction particles that participate in three fundamental forces.

There are four forces in total, and they define the standard model of fundamental physics: the strong force, the weak force, the electromagnetic force, and the gravitational force. If the first three interact with each other, gravity is (for now) a special case.

Although this is the force we are most familiar with, physicists have struggled to find a place for it in the Standard Model, even though the particle that carries gravity (theoretically the “graviton”) has not yet been observed. That’s why it’s not in the table below:

The particle of interest to physicists here is called the W-boson, one of the sources of the weak force. To calculate its mass, physicists relied on an analysis of about 4 million W bosons produced at the Tevatron (the name of the CDF particle accelerator) between 2002 and 2011.

This discovery comes at a time when the physics community is eager to find flaws in the standard model of particle physics. Indeed, the Standard Model is known to be incomplete, leaving several great mysteries unsolved, such as the nature of dark matter.

“This is a monumental work,” said Frank Wilczek, a Nobel Prize-winning physicist at the Massachusetts Institute of Technology. “Overall, I feel like we are approaching a point where something is about to break,” El-Khadra said. “We are approaching the time when we can really go beyond the standard model.”

Caution advised

However, no one drinks champagne yet. While the new measurement of the mass W, taken in isolation, differs sharply from the prediction of the Standard Model, other experiments weighing the W boson have yielded less impressive results.

For example, in 2017 the ATLAS experiment at the Large Hadron Collider in Europe (a particle accelerator with a circumference of 27 km, the largest and most powerful in the world) measured the mass of a W particle and found that it is only slightly heavier than what the Standard Model says.

It is important to understand the difference in measurements between the two laboratories. Indeed, according to Guillaume Unal, a physicist at CERN (the laboratory that houses the Large Hadron Collider), “the W boson must be the same on both sides of the Atlantic.”

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