Scientists are using trapped ions in cutting-edge experiments to hunt for signs of an undiscovered particle that might help unravel the mystery of dark matter.
The Standard Model of particle physics offers an exceptionally precise description of the fundamental components that form all visible matter, including the particles that make up everything around us and ourselves. It also defines the basic forces that govern interactions between these elementary particles.
“The Standard Model is currently the best explanation of the universe, but we know it cannot explain everything,” says Diana Prado Lopes Aude Craik, Physics Professor at ETH Zurich. She points to dark matter as an example of “one of the biggest mysteries in physics today.”
Observations from astronomy indicate that the visible matter we can detect does not fully account for the way galaxies spin. Because of this, physicists believe that the majority of the universe’s mass is made up of an unknown type of matter. This has led to a search for theories that can extend beyond what the Standard Model currently explains.
Among the leading ideas are theories that propose a new, fifth force of nature to accompany the four known fundamental forces: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. One possibility is that a previously unknown force exists between neutrons in the atomic nucleus and electrons in the surrounding electron cloud. This hypothetical force might be transmitted by a new particle, in a manner similar to how photons are responsible for carrying the electromagnetic force.
Measuring the atom with precision
Researchers have long conducted experiments using particle accelerators, such as at CERN in Geneva, to search for new particles beyond the Standard Model. Aude Craik and her colleagues in Professor Jonathan Home’s research group at the ETH Institute of Quantum Electronics are taking a different approach.
“As atomic physicists, we can measure the atom with extremely high precision,” she explains. “Therefore, the idea is to search for this new force between the neutron and the electron using precision atomic spectroscopy.” The Zurich-based team is collaborating with research groups in Germany and Australia on this project.
“If this force really exists in the atom, then its strength is proportional to the number of neutrons in the atomic nucleus,” explains Luca Huber, a doctoral student in the research team. “That’s why we are experimenting with isotopes to detect this hypothetical force.”
Isotopes are types of the same atom that differ only in the number of neutrons in the atomic nucleus. This means that isotopes have the same number of protons and electrons and are therefore chemically identical, but they each have different masses.
As a result, the total force experienced by the electrons in different isotopes should vary slightly due to the different number of neutrons. This can be measured by examining the energy levels on which the electrons move within the atom. Specifically, researchers expect the new force to cause slight shifts in the energy levels between different isotopes.
Studying calcium isotopes in a precision ion trap
“To determine these energy shifts, we measure the frequency of the light emitted when our isotopes transition between two energy levels,” explains Aude Craik.
This measurement requires an ion trap, where electromagnetic fields hold a single charged isotope in place and a laser excites it to a higher energy state. Specifically, the researchers used five stable, singly-charged calcium isotopes in their experiments. Each isotope contained 20 protons, but the number of neutrons ranged from 20 to 28. In the laboratory, the researchers were able to determine the shifts in energy levels of these isotopes with an accuracy of 100 millihertz, which is one hundred times more precise than the best previous measurements. But how did they achieve this?
“We trapped two isotopes at the same time in the ion trap and measured them together,” explains Huber. This allowed them to drastically reduce the interfering noise during the frequency measurement.
However, despite this precision, further experiments were needed to advance the search for new physics. While the team in Zurich experimented with singly charged calcium isotopes, a research group led by Piet Schmidt at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig used the same isotopes but in a multiply charged state.
The German group measured a different transition in these highly charged calcium ions with similar accuracy to the Zurich team. A third group, led by Klaus Blaum at the Max Planck Institute for Nuclear Physics in Heidelberg, measured the ratios of nuclear masses between these isotopes with extreme precision.
More precise constraints determined
To interpret this result correctly, other research teams in Germany and Australia carried out precision calculations. Their results show that well-understood nuclear effects explain only part of the deviation. Another possible cause is nuclear polarization, a type of deformation of the atomic nucleus caused by electrons, which has been little studied so far. Its complex calculation shows that nuclear polarization could be large enough to explain the measured nonlinearity within the limits of the Standard Model.
“We can’t say that we’ve discovered new physics here,” emphasizes Aude Craik. “However, we know how strong the new force can be at most because we would have seen it otherwise in our measurements, even with the uncertainties”. The researchers can now set bounds on the possible values for the mass and charge of the hypothetical particle that would transmit this new force.
The researchers are now working to further improve the accuracy of their results. “We are currently measuring a third energy transition in the calcium isotopes,” says Huber, “and doing so with even greater precision than before.” With this, they aim to expand the King plot from two dimensions into a three-dimensional diagram. “We hope that this will help us overcome the theoretical challenges and make further progress in the search for this new force,” says Aude Craik.
Reference: “Nonlinear Calcium King Plot Constrains New Bosons and Nuclear Properties” by Alexander Wilzewski, Lukas J. Spieß, Malte Wehrheim, Shuying Chen, Steven A. King, Peter Micke, Melina Filzinger, Martin R. Steinel, Nils Huntemann, Erik Benkler, Piet O. Schmidt, Luca I. Huber, Jeremy Flannery, Roland Matt, Martin Stadler, Robin Oswald, Fabian Schmid, Daniel Kienzler, Jonathan Home, Diana P. L. Aude Craik, Menno Door, Sergey Eliseev, Pavel Filianin, Jost Herkenhoff, Kathrin Kromer, Klaus Blaum, Vladimir A. Yerokhin, Igor A. Valuev, Natalia S. Oreshkina, Chunhai Lyu, Sreya Banerjee, Christoph H. Keitel, Zoltán Harman, Julian C. Berengut, Anna Viatkina, Jan Gilles, Andrey Surzhykov, Michael K. Rosner, José R. Crespo López-Urrutia, Jan Richter, Agnese Mariotti and Elina Fuchs, 10 June 2025, Physical Review Letters.
DOI: 10.1103/PhysRevLett.134.233002
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22 Comments
Physicists Close In on the Fifth Force That Could Unlock the Mystery of Dark Matter.
VERY GOOD.
Please ask the physicists to think deeply:
1. Is your theoretical foundation correct?
2. Is your classification of forces scientific?
The science works, so your questions may be inapplicable.
Your next comment superstition is obviously inapplicable – most particles seen today were produced by natural processes during the hot big bang.
Thank you for browsing and commenting.
Please think deeply:
1. Where does the energy of the Big Bang come from?
2. Which is easier to understand mathematically, the Big Bang or spin from topology?
Although mathematics is not physics, the interpretation of physical phenomena must not be arbitrarily imagined without mathematics.
Don’t feed Zhang the troll, he pops in to every single STD article that has anything to do with physics and loves spouting off a bunch of random ish about topological vortexes without ever making any actual points or offering any real evidence. Don’t feed the trolls.
Thank you for browsing and commenting.
Although mathematics is not physics, the interpretation of physical phenomena must not be arbitrarily imagined without mathematics. Real evidence IS that two sets of cobalt-60 are artificially rotated in opposite directions, whether symmetrical or not, they are two mirror images of each other.
If Mr. Kindlin really believes the evidence, please browse https://zhuanlan.zhihu.com/p/1924133848171648046 (If the link is not blocked).
The particles in space come from God, Demons, or Angels.
,etc.
Your comment is awaiting moderation.
That is true and confirmed in this related article:
Dark Matter in Form of WIMPs Hits Humans Once a Minute
Thank you for browsing and commenting.
However, it should be noted that the fact you have observed may be that “the sun revolves around the earth” and “parity is violated” in your opinion.
The whole world, all the parents, all the kids, all the teachers, all their priests, all the University scholars, all thought the Sun goes around the Earth. They thought so because they were told so and, they could see it.
When someone tells you your little idea is wrong, you don’t like that – even when your belief isn’t even your idea.
Long overdue, on June 29 I finally uploaded a new low-budget video demonstrating the locally induced (by some still unidentified higher source) radiant-pulsing-angular-lines-of-attractive-force nature of gravity to my old video channel (https://odysee.com/@charlesgshaver:d/5Gravity:c). Hypothesizing that free-wheeling end mounted aluminum disks would be compelled to rotate independent of a center mounted aluminum bar forced to rotate CW or CCW, by their local fields of gravity engaging with earth’s ambient field of gravity, like ‘whiskers brushing against whiskers,’ my experiments even explained to me how inertia works. After just reading the article above, I now postulate that at all levels, from subatomic to galactic, in some ratio I have not yet (if ever?) calculated, the mass of an object times it’s individual angular velocity determines the strength of it’s local field of gravity, eliminating any need for dark energy, dark matter or a “fifth force” to explain all of what holds the universe together, with the age and size thereof still in need of accurate determination.
Thank you for browsing and commenting.
However, it should be noted that the fact you have observed may be that “the sun revolves around the earth” and “parity is violated” in your opinion.
Unless you can publish peer reviewed predictions that your can predict all that the standard model does and some more, all of that is irrelevant.
Thanks for the feedback. What is irrelevant, Professor Larsson, is academics who’ve lost the curiosity, dedication and objectivity needed to perform their own experiments. Publishing can be faked and mathematics can be manipulated to prove just about anything but, if faithfully replicated, an experiment can have only one of two possible outcomes; to prove a theorem or to disprove it.
@Torbjörn Larsson
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Before I verify, please use your knowledge gained from peer-reviewed publications that you believe in to inform the public:
1. Are two sets of cobalt-60 manually rotating in opposite directions, whether symmetrical or not, two objects that are mirror images of each other?
2. Do you see the sun revolving around the earth, or does the earth revolve around the sun?
YES or NO.
Interesting work. Since they are measuring this to fantastic precision the possible new force, as they point out here, must have a very small upper bound for possible strength. We already can explain the interaction of electrons and nuclei to great precision with known science. I wonder what they hope to find?
“Nonlinearities in King plots (KP) of isotope shifts (IS) can reveal the existence of beyond-standard-model (BSM) interactions that couple electrons and neutrons. However, it is crucial to distinguish higher-order standard model (SM) effects from BSM physics.”
They hope to find an isotope shift plot non-linearity that the standard model – up to any order – cannot explain. That could be a sign of beyond-standard-model physics, in their case in the form of putative “dark matter bosons”.
Other experiments looks elsewhere for dark matter candidates. It is hard to say what could succeed, so it is good if they try to cover as much ground as possible.
They haven’t seen anything that cannot be explained by the standard model, but perhaps they can improve on it as they “identify the little-studied nuclear polarization as the only remaining SM contribution that may be large enough to explain [an observed non-linearity].”
Although mathematics is not physics, physics must never abandon mathematics to indulge in unrestrained speculation. The demarcation between science and pseudoscience lies neither in mainstream peer-reviewed publications, nor in prestigious journals, nor in so-called impact factors (IF) and Nobel Prizes—but in whether material motion adheres to the dynamic evolution governed by the combined PCT (Parity, Charge, Time) symmetry. From cosmic accretion discs to quantum spin, vortex structures are ubiquitous. Topological vortices, satisfying the combined PCT symmetry, provide profound insights into the nature of spacetime motion. There is absolutely no need to distort our understanding of the world with imagined parity violation that mislead science.
The DESI program discovered that DE weakens over time, making it a variable instead of a constant. They’re still working on the why of this observation.
The JWST is already producing observational results that cannot be accounted for by the standard model, including galaxy and supermassive black hole evolution at high redshift.
https://scitechdaily.com/when-the-universe-broke-the-rules-webb-spots-impossible-galaxies-at-cosmic-dawn/