Center for Axion and Precision Physics

The Center for Axion and Precision Physics or CAPP is a flagship research center under the Institute for Basic Science (IBS) in South Korea, dedicated to uncovering the nature of Dark Matter, the vast invisible component of the universe, and investigating the cause of the matter-antimatter asymmetry existing in the universe.^[1][2] Modern measurements indicate that Dark Matter constitutes approximately 25% of the total energy-mass of the universe. The axion particle was proposed as a solution to the Strong CP problem. On the other hand, as part of precision physics, measuring the Electric Dipole Moment or EDM is a direct experimental probe of this Strong CP problem.^[3]

Establishment and mission

CAPP was formally established on October 16, 2013. It is part of the Institute for Basic Science (IBS), a major government basic science research agency in South Korea. IBS was established in 2011 with the goal of advancing basic science research in South Korea.^[4] CAPP is one of the 33 research centers operated under IBS.^[5]

CAPP's physical location is in the city of Daejeon, South Korea's hub for science and technology. It is located on the Munji Campus of the Korea Advanced Institute of Science and Technology (KAIST). The center's official address is Office C301/C302, Creation Hall (3F), KAIST Munji Campus, 193 Munji-ro, Yuseong-gu, Daejeon 34051, South Korea.^[6]

The center's founder and current director is Professor Yannis K. Semertzidis. He also serves a dual role as a professor in the Department of Physics at KAIST.^[7]

CAPP represents a successful institutional transfer of specialized basic physics knowledge and leadership from the United States to Korea.^[8]

Research

Cavity Haloscope

CAPP's main axion search strategy is dependent on a special experimental apparatus called a "haloscope". This method was first proposed by the theoretical physicist Pierre Sikivie.^[9][10]

CAPP's main axion experiments and results

CAPP-8TB (CULTASK)

This was one of CAPP's early flagship experiments. The name "CULTASK" comes from "CAPP's Ultra Low Temperature Axion Search in Korea" and it was also dubbed the "coldest axion experiment". This experiment utilized an 8 Tesla (8T) superconducting magnet.^[11][12][13]

Its most important result was published in the journal Physical Review Letters (PRL) in 2020. This paper gained wide recognition as the "First High-Sensitivity Dark Matter Axion Hunting Results from South Korea". This experiment conducted a search in the mass range of 6.62 to 6.82 ${\displaystyle \mu {\text{eV}}}$, equivalent to a frequency of 1.6 to 1.65 GHz.^[14][15]

CAPP-MAX (CAPP-12TB)

This is CAPP's current flagship axion experiment. The "CAPP-MAX (Main Axion eXperiment)" was formerly known as "CAPP-12TB". This experiment uses a 12 Tesla (12T) magnet and the aforementioned 37-liter ultralight-weight cavity. Its result was published in the journal Physical Review X (PRX) in 2024. This research conducted a comprehensive search in the 1.025 to 1.185 GHz (4.24 to 4.91 ${\displaystyle \mu {\text{eV}}}$ frequency range. The results of this experiment imposed "the most stringent exclusion limits on axion-photon coupling in this frequency range". This was the "first comprehensive search... near DFSZ sensitivity above 1 GHz". Even before this, in 2023, results from CAPP-12TB of a DFSZ-sensitive search in the 4.51-4.59 ${\displaystyle \mu {\text{eV}}}$ range were published in Physical Review Letters.^[16][17][18]