January 26, 2023

2021 – A Year Physicists Asked, “What Lies Beyond the Standard Model?”

Experiments at the Large Hadron Collider in Europe, like the ATLAS calorimeter seen here, are offering more accurate measurements of basic particles. Credit: Maximilien Brice, CERN
If you ask a physicist like me to describe how the world works, my lazy response may be: “It follows the Standard Model.”
The Standard Model describes the essential physics of how the universe works. It has actually withstood over 50 trips around the Sun regardless of experimental physicists continuously probing for fractures in the designs structures.
With few exceptions, it has actually stood up to this examination, passing speculative test after speculative test with flying colors. But this wildly successful design has conceptual gaps that suggest there is a bit more to be found out about how deep space works.

Neutrinos represent three of the 17 essential particles in the Standard Model. I study the homes of interactions in between neutrinos and normal matter particles.
In 2021, physicists around the globe ran a number of experiments that penetrated the Standard Model. Teams determined standard parameters of the model more exactly than ever previously. Others investigated the fringes of understanding where the very best experimental measurements dont rather match the predictions made by the Standard Model. Groups constructed more effective technologies designed to press the model to its limits and possibly find new particles and fields. If these efforts work out, they could lead to a more complete theory of the universe in the future.
The Standard Model of physics enables researchers to make exceptionally precise forecasts about how the world works, but it does not discuss whatever. Credit: CERN
Filling holes in Standard Model
In 1897, J.J. Thomson found the very first basic particle, the electron, using nothing more than glass vacuum tubes and wires. More than 100 years later on, physicists are still discovering brand-new pieces of the Standard Model.
The Standard Model is a predictive framework that does 2 things. First, it discusses what the basic particles of matter are. These are things like electrons and the quarks that make up protons and neutrons. Second, it predicts how these matter particles communicate with each other utilizing “messenger particles.” These are called bosons– they consist of photons and the famous Higgs boson– and they communicate the fundamental forces of nature. The Higgs boson wasnt discovered until 2012 after years of work at CERN, the huge particle collider in Europe.
The Standard Model is incredibly proficient at forecasting numerous aspects of how the world works, but it does have some holes.
Notably, it does not include any description of gravity. While Einsteins theory of General Relativity explains how gravity works, physicists have not yet discovered a particle that conveys the force of gravity. A correct “Theory of Everything” would do everything the Standard Model can, however also include the messenger particles that interact how gravity communicates with other particles.
Another thing the Standard Model cant do is describe why any particle has a specific mass– physicists must determine the mass of particles straight utilizing experiments. Just after experiments offer physicists these precise masses can they be utilized for predictions. The better the measurements, the better the predictions that can be made.
Recently, physicists on a team at CERN determined how strongly the Higgs boson feels itself. Another CERN team also determined the Higgs bosons mass more precisely than ever previously. There was also progress on measuring the mass of neutrinos. Physicists know neutrinos have more than zero mass however less than the quantity presently noticeable. A team in Germany has continued to refine the strategies that could enable them to straight determine the mass of neutrinos.
Projects like the Muon g-2 experiment highlight disparities in between speculative measurements and forecasts of the Standard Model that point to issues somewhere in the physics. Credit: Reidar Hahn, Fermilab
Hints of brand-new forces or particles
In April 2021, members of the Muon g-2 experiment at Fermilab announced their first measurement of the magnetic moment of the muon. The muon is one of the fundamental particles in the Standard Model, and this measurement of among its properties is the most precise to date. Due to the fact that the measurement didnt perfectly match the Standard Model prediction of the magnetic minute, the factor this experiment was important was. Generally, muons do not behave as they should. This finding might point to undiscovered particles that interact with muons.
Concurrently, in April 2021, physicist Zoltan Fodor and his coworkers revealed how they used a mathematical method called Lattice QCD to precisely calculate the muons magnetic minute. Their theoretical prediction is different from old forecasts, still works within the Standard Model and, importantly, matches speculative measurements of the muon.
The difference in between the formerly accepted predictions, the new forecast and this new outcome need to be reconciled before physicists will understand if the speculative outcome is really beyond the Standard Model.
New tools will assist physicists browse for dark matter and other things that could assist explain mysteries of the universe. Credit: Mark Garlick
Upgrading the tools of physics
Physicists need to swing in between crafting the mind-bending concepts about truth that make up theories and advancing innovations to the point where new experiments can evaluate those theories. 2021 was a big year for advancing the experimental tools of physics.
The worlds biggest particle accelerator, the Large Hadron Collider at CERN, was shut down and went through some substantial upgrades. At these incredible energies, physicists may discover brand-new particles that were too heavy to see at lower energies.
Some other technological developments were made to help the search for dark matter. Numerous astrophysicists believe that dark matter particles, which do not currently fit into the Standard Model, could address some outstanding questions regarding the way gravity bends around stars– called gravitational lensing– along with the speed at which stars rotate in spiral nebula. Projects like the Cryogenic Dark Matter Search have yet to find dark matter particles, but the groups are establishing larger and more sensitive detectors to be released in the near future.
Particularly pertinent to my deal with neutrinos is the advancement of enormous new detectors like Hyper-Kamiokande and DUNE. Using these detectors, scientists will hopefully have the ability to answer questions about an essential asymmetry in how neutrinos oscillate. They will also be utilized to look for proton decay, a proposed phenomenon that certain theories anticipate ought to take place.
2021 highlighted some of the methods the Standard Model fails to describe every mystery of deep space. But new measurements and brand-new innovation are helping physicists move forward in the search for the Theory of Everything.
Written by Aaron McGowan, Principal Lecturer in Physics and Astronomy, Rochester Institute of Technology.
This short article was first released in The Conversation.

Neutrinos represent 3 of the 17 essential particles in the Standard Model. An appropriate “Theory of Everything” would do whatever the Standard Model can, but likewise include the messenger particles that interact how gravity communicates with other particles.
Another thing the Standard Model cant do is discuss why any particle has a particular mass– physicists need to determine the mass of particles directly utilizing experiments. The muon is one of the basic particles in the Standard Model, and this measurement of one of its residential or commercial properties is the most precise to date. Lots of astrophysicists believe that dark matter particles, which dont currently fit into the Standard Model, could respond to some impressive questions regarding the way gravity flexes around stars– called gravitational lensing– as well as the speed at which stars rotate in spiral galaxies.

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