Could Dark Matter Lie Beyond The Portal?

A dark axion portal could link the observable Universe to dark matter, which occupies 70 percent of the Universe but remains poorly understood.

AsianScientist (Mar. 31, 2017) – Scientists at the Center for Theoretical Physics of the Universe at the Institute for Basic Science (IBS) have proposed that dark matter is linked to the known Universe described by the Standard Model of particle physics by portals. Their findings have been published in Physical Review Letters.

Once upon a time, the Universe was just a hot soup of particles, both observable and ‘dark.’ Billions of years later, scientists have cataloged 17 types of visible particles in the Standard Model, with the Higgs boson being the most recent particle to be recognized. However, they are still struggling to detect the hidden particles, the ones that constitute the dark sector of the Universe.

Physicists have plenty of ideas about what these dark sector particles might look like. One candidate is the axion, which is a very light particle that could resolve some theoretical problems of the Standard Model. Another candidate is the dark photon: A very light particle which shares some properties with the photon, the constituent of visible light. However, while photons couple to the electromagnetic charge, dark photons couple to the so-called dark charge, that might be carried by other dark sector particles.

Physicists believe that the dark sector communicates with the Standard Model via portals. For example, a vector portal would allow the mixing between photons and dark photons, and an axion portal connects axions and photons. There are only several possible portals physicists have identified, and each portal is a major tool in theoretical and experimental studies in searching for dark sector particles.

In the present study, a team of IBS scientists hypothesized the existence of a new portal that connects dark photons and axions named the “dark axion portal.” The central idea of the dark axion portal is based on the observation that new heavy quarks may also have a dark charge that couples to the dark photon. Through the heavy quarks, axion, photon, and dark photon can interact with each other.

Through portals, it is possible to explore the dark sector particles using the Standard Model particles. Portals thus play a basic and critical role in the study of the dark sector particles both theoretically and experimentally. Credit: IBS.

IBS scientists imagine that the dark axion portal could generate ideas for new experiments. So far, the axion search has been performed using only the axion portal, which connects the axion to a pair of photons (axion-photon-photon coupling). Similarly, the dark photon search has been performed using a different portal, namely a vector portal, which allows a small mixing between the dark photon and photon.

“The dark axion portal suggests the first meaningful connection between the two physics, which have been studied separately: It connects the dots. This will allow reinterpretation of the previous data, and potentially make a breakthrough in the axion and dark photon searches,” explained study corresponding author, Dr. Lee Hye-Sung.

The article can be found at: Kaneta et al. (2017) Portal Connecting Dark Photons and Axions.


Source: Institute for Basic Science; Photo: Shutterstock.
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