New result from LHCb experiment challenges cutting-edge theory in physics

The LHCb collaboration at CERN has discovered that particles do not behave as they should according to the guiding theory of particle physics – the Standard Model.

The Standard Model of Particle Physics predicts that particles called beauty quarks, which are measured in the LHCb experiment, should decay into muons or electrons in equal measure. However, the new result suggests that this may not be happening, which could indicate the existence of new particles or interactions not explained by the Standard Model.

Physicists from Imperial College London and the Universities of Bristol and Cambridge conducted the data analysis to produce this result, with funding from the Science and Technology Facilities Council. The result was announced today at the Moriond Electroweak Physics conference and published as a pre-print.

Beyond the standard model

The Standard Model is the best current theory of particle physics, describing all of the known fundamental particles that make up our Universe and the forces with which they interact.

However, the Standard Model cannot explain some of the deepest mysteries in modern physics, including what dark matter is made of and the imbalance of matter and antimatter in the universe.

So the researchers looked for particles that behave differently from what one would expect in the Standard Model, to help explain some of these mysteries.

Dr Mitesh Patel, from the Department of Physics at Imperial Oil and one of the main physicists behind the measurement, said: “We were actually shaking when we first looked at the results, we were. very excited. Our hearts beat a little faster.

“It is too early to tell if this is truly a deviation from the Standard Model, but the potential implications are such that these results are the most exciting thing I have done in 20 years in the field. . It has been a long journey to get here. . “

Nature building blocks

Today’s results were produced by the LHCb experiment, one of four huge particle detectors in CERN’s Large Hadron Collider (LHC).

The LHC is the world’s largest and most powerful particle collider – it accelerates subatomic particles to almost the speed of light, before crushing them into each other. These collisions produce an explosion of new particles, which physicists then record and study to better understand the basic building blocks of nature.

The updated measurement questions the laws of nature that treat electrons and their heavier cousins, muons, identically, except for small differences due to their different masses.

According to the Standard Model, muons and electrons interact with all forces in the same way, so beauty quarks created at LHCb should decay into muons as often as electrons.

But these new measurements suggest that decays could occur at different rates, which could suggest never-before-seen particles moving the muon scales away.

Imperial Ph.D. Student Daniel Moise, who first announced the results at the Moriond Electroweak Physics conference, said: “The result offers an intriguing clue of a new fundamental particle or force that interacts in a way. that particles currently known to science do not.

“If this is confirmed by further measurements, it will have a profound impact on our understanding of nature at the most fundamental level.”

No advance

In particle physics, the gold standard for discovery is five standard deviations – meaning there is a 1 in 3.5 million chance that the result is fluke. This result corresponds to three deviations, which means that there is always a 1 in 1000 chance that the measurement is a statistical coincidence. It is therefore too early to draw any firm conclusions.

Dr Michael McCann, who also played a leading role in the Imperial team, said: “We know there must be new particles to be discovered because our current understanding of the Universe is insufficient to fully understand. respects – we don’t know what 95% of the Universe is made of, or why there is such a big imbalance between matter and antimatter, nor do we understand the patterns in the properties of the particles we know.

“Although we will have to wait for confirmation of these results, I hope that one day we can see this as a turning point, where we have started to answer some of these fundamental questions.”

It is now up to the LHCb collaboration to further verify their results by collecting and analyzing more data, to see if evidence for some new phenomena remains. The LHCb experiment is expected to start collecting new data next year, after an upgrade of the detector.