South Korea debuts first search for DFSZ axion dark matter

A South Korean research team at the Center for Axion and Precision Physics Research (CAPP) at the Institute for Basic Science (IBS) recently announced the most advanced experimental setup for searching for axions. The group has successfully taken its first step towards the search for Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) axion dark matter originating from the Grand Unification Theory (GUT). Not only that, the IBS-CAPP experiment setup allows far greater search speed compared to other axion search experiments in the world.

The notion that physics is “dead” has been a recurring opinion throughout history. In the late 19th century, William Thompson, also known as Lord Kelvin, mistakenly believed that there would be no new discovery in physics after 1900. Likewise, some have believed that there were no new particles to be found after the discovery of neutrons on The 1930s. . Even today, some worry that modern theoretical physics is at a dead end.

However, this is far from the truth. Our current frontier of knowledge in physics, the Standard Model, is only able to explain about 5% of the universe, with the other 95% being made up of dark matter and dark energy.

The current standard model also has limitations in explaining problems such as the strong CP (charge conjugation parity) problem. The problem arises from the observation that the strong force, as described by quantum chromodynamics (QCD), does not appear to break CP symmetry, while the electroweak force does slightly break CP symmetry. This is contrary to the Standard Model, which predicts that CP symmetry should be broken by the strong force at a level much larger than that observed.

One proposed solution to the problem involves the existence of hypothetical particles called axions, which can resolve the discrepancy between the predicted and observed levels of CP violation in the strong force. The action is one of the strongest candidates for dark matter. The discovery of axion dark matter would undoubtedly be a landmark event in human history.

Currently, two different “beyond the standard model” proposals exist to explain the strong CP problem. The main difference between the two models is that they predict different types of connections between actions and other particles. In the Kim-Shifman-Vainshtein-Zakharov (KSVZ) model, axions are primarily coupled to heavy quarks, while in the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model they are coupled to Standard Model quarks and leptons via Higgs bosons.

Like dark matter, axions have very weak (or small) interactions with ordinary matter, so searching for them can be difficult. A common approach involves microwave cavity experiments. These experiments use a strong magnetic field to convert axions (if they exist) into resonant electromagnetic waves, which are then detected using a receiver. The action’s mass can then be calculated from the detected wave’s frequency.

Since axion mass is unknown, physicists must broaden their search and scan a large range of frequencies.

The problem is exacerbated when searching for a DFSZ action, which requires much greater sensitivity than the KSVZ action. In microwave cavity search experiments, it requires an exponentially higher search time to achieve higher sensitivity, and therefore searching for a DFSZ axion is out of reach for almost all existing experimental setups.

As a result, while a few axion search experiments have searched for signals in the KSVZ axion sensitivity ranges, so far the only experiment capable of achieving the sensitivity required to search for DFSZ axions was the Axion Dark Matter eXperiment (ADMX). of the ADMX collaboration. This makes IBS-CAPP the second group in the world to search for action with DFSZ sensitivity.

The IBS-CAPP group used a 12T magnet, which is more powerful than the 8T magnet used by ADMX. To minimize the background noise, the experimental setup was kept at near absolute zero temperature.

In addition to using a more powerful magnet, the IBS-CAPP experiment used quantum technologies and a more efficient computational method to curate the data. This allowed IBS-CAPP to search for DFSZ stocks at 3.5 times the speed of the ADMX setup.

The latest publication from IBS-CAPP describes the demonstration of their new setup for DFSZ axion searches from 1 March to 18 March 2022. As a result, the group was able to exclude axion dark matter around 4.55 µeV at DFSZ sensitivity. The findings are published in the journal Physical review letters.

“The discovery of axion will allow us to understand up to 32% of the mass-energy of the universe, up from the 5% offered by the current standard model,” says research fellow KO Byeong Rok at IBS-CAPP. He added, “We plan to take advantage of the lightning-fast speed of our experimental setup to rapidly search for DFSZ actions at the broad frequency ranges of 1 to 2 GHz.”

It is hoped that the discovery of the axion will support the Grand Unification Theory (GUT), which unifies the three fundamental forces – strong, weak and electromagnetism. It is believed that the three fundamental forces were united and indistinguishable from each other at the earliest moment after the Big Bang, under conditions greater than those achievable in the Large Hadron Collider today. It is hoped that GUT will act as a stepping stone to the coveted Theory of Everything (TOE) that has eluded theoretical physicists all these years.

Director Yannis SEMERTZIDIS of IBS-CAPP said: “We are very grateful for all the funding and support that the Institute for Basic Science and South Korean taxpayers provided for this project. It is thanks to them that South Korea is now hosting the most advanced action research experimental facility in the world. If axion exists, I have no doubt that it will be found here in South Korea.”