The Standard Model of particle physics explains the basic physics of how the universe works. But there are loopholes in it. In 2021, scientists are highlighting some of the ways the Standard Model can’t explain every mystery of the universe. This, combined with new technology developed over the past year, is helping physicists advance their search for a theory of everything.
In 2021, physicists around the world conducted some interesting experiments to examine the Standard Model. Teams measured the model’s key parameters more accurately than ever before. Others have discovered the limits in which the best experimental measurements do not quite match the predictions of the Standard Model. Finally, the groups have built more powerful techniques designed to push the model to its limits and possibly discover new particles and fields.
In 1897, J.J. Thomson discovered the first fundamental particle, the electron, using vacuum glass tubes and wires. More than 100 years later, physicists are still discovering new pieces of the Standard Model.
What (cannot) do the Standard Model
The Standard Model is a predictive framework that does two things. First, it explains what the fundamental particles of matter are. These are things like electrons and quarks that make up protons and neutrons. Second, it predicts how particles of matter will interact with each other using “messenger particles”. Called bosons – including photons and the famous Higgs boson – they transmit the fundamental forces of nature. The Higgs boson was discovered only in 2012 after decades of work at CERN, the massive particle accelerator.
The Standard Model is incredibly good at predicting many aspects of how the world works, but it has some loopholes. Notably, it does not contain a description of gravity. Although Einstein’s general theory of relativity describes how gravity works, physicists have yet to discover the particle that transmits gravity.
Another thing the Standard Model can’t do is explain why a particle has a certain mass – physicists have to measure the mass of the particles directly using experiments. Only after experiments have given physicists these exact masses can they be used for predictions. The better the measurements, the better the predictions that can be made.
Neutrino en muonen
Recently, team physicists at CERN Measure how strong the Higgs boson feels for itself. Another CERN team also owns the Higgs boson mass Measured more accurately than ever before. Finally, there has also been progress in measuring the mass of neutrinos. Physicists know that neutrinos have a mass greater than zero, but less than the amount that can currently be detected. A team in Germany has continued to improve techniques that allow them to directly measure the mass of neutrinos.
In April 2021 Members of the Muon g-2 experiment at Fermilab announced their first measurement of the muon’s magnetic moment. The muon is one of the fundamental particles in the Standard Model, and this measurement of one of its properties is the most accurate to date. The reason for the importance of this experiment was that the measurement did not exactly match the prediction of the Standard Model of magnetic moment. Muons basically don’t behave as they should. This result could indicate the interaction of undetected particles with muons.
But at the same time, in April 2021, physicist Zoltan Fodor and his colleagues demonstrated how they used a mathematical method called Lattice QCD to accurately calculate the muon’s magnetic moment. Their theoretical prediction is different from the older predictions, still works within the Standard Model and, most importantly, is consistent with experimental measurements of the muon. The new measurement must now be reconciled with the new prediction before physicists know if the experimental result is truly outside the Standard Model.
2021 was also an important year for the development of experimental tools for physics. First, the world’s largest particle accelerator, the Large Hadron Collider at CERN, has been shut down, and has undergone some substantial improvements. The physicists restarted the facility in October, and plan to begin collecting the next data in May 2022. The upgrades have increased the power of the accelerator so that it can cause collisions at 14 TeV, up from the previous limit of 13 TeV. This means that the thrusts of tiny protons traveling in groups around the circular accelerator together carry the same amount of energy as a 360,000-kilogram passenger train traveling at 100 miles per hour. With this huge amount of energy, physicists are able to discover new particles that were too heavy to see until now.
Some other technological advances have been made to aid the search for dark matter. Many astrophysicists believe that dark matter particles, which currently do not fit the Standard Model, could answer some open questions about how gravity bends around stars – called gravitational lensing – and the speed with which stars rotate in spiral galaxies. Projects like the Cryogenic Dark Matter Search have yet to find dark matter particles, but teams are developing larger, more sensitive detectors that will be deployed in the near future.
Also amazing is the development of massive new detectors such as Hyper Kamiokandi in a Dunn. With the help of these detectors, scientists can answer questions about a fundamental asymmetry in how neutrinos oscillate. They will also be used to look at proton decay, a proposed phenomenon that some theories say should occur.
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