Scientists propose a new method to search for bright dark matter

Scientists propose a new method to search for bright dark matter

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A 2021 map of dark matter using the Weak Gravitational Lensing Dataset. Credit: Dark Energy Research.

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A 2021 map of dark matter using the Weak Gravitational Lensing Dataset. Credit: Dark Energy Research.

New research in Physical examination letters (PRL) proposed a new method to detect light dark matter candidates using laser interferometry to measure the oscillatory electric fields generated by these candidates.

Dark matter is one of the most pressing challenges in modern physics, with dark matter particles being elusive and difficult to detect. This has led scientists to come up with new and innovative ways to search for these particles.

There are several candidates for dark matter particles, such as WIMPs, light dark matter particles (axions), and the hypothetical gravitino. Bright dark matter, including bosonic particles such as the axion of QCD (quantum chromodynamics), has become a subject of interest in recent years.

These particles usually have suppressed interactions with the standard model, making them difficult to detect. However, knowing their characteristics, including their wavelike behavior and coherent nature on galactic scales, helps to design more efficient experiments.

In the new one PRL study, researchers from the University of Maryland and Johns Hopkins University proposed Galactic Axion Laser Interferometer Leveraging Electro-Optics, or GALILEO, a new approach to detect both axion and dark photon dark matter over a wide mass range.

Lead researcher Reza Ebadi, a graduate student at the Quantum Technology Center (QTC) at the University of Maryland, spoke to about the research and their motivation for developing this new approach, “Although the Standard Model provides successful explanations for phenomena ranging from the subnuclear distances up to the size of the universe, it is not a complete explanation of nature.”

“It fails to explain the cosmological observations that infer the existence of dark matter. We aim to gain insight into physical theories operating on galactic scales using small laboratory experiments.”

Axions and axion-like particles

Axions and axion-like particles were originally proposed to solve problems in particle physics, such as the strong charge parity (CP) problem. This problem arises from the observation that the strong force does not appear to exhibit a particular type of symmetry violation, called CP violation, as much as theory predicts it should.

This theoretical framework naturally gives rise to axion-like particles that share similar properties with axions, both being bosons.

Axions and axion-like particles are predicted to have very low masses, typically ranging from microelectronvolts to millielectronvolts. This makes them suitable candidates for bright dark matter, as they can exhibit wave-like behavior on galactic scales.

In addition to their low mass, axions and axion-like particles interact very weakly with ordinary matter, making them difficult to detect using conventional means.

These are some of the reasons why the researchers chose to detect these particles in their experimental setup. However, the method depends on the oscillatory electric fields produced by these particles.

In regions of significant dark matter density, axions and ALPs can undergo coherent oscillations. These coherent oscillations can lead to detectable signals, such as oscillating electric fields, which the proposed GALILEO experiment aims to measure.

Estimated sensitivity of the GALILEO experiment to search for axions (left) and dark photons (right) for dark matter. credit: Physical examination letters (2024). DOI: 10.1103/PhysRevLett.132.101001

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Estimated sensitivity of the GALILEO experiment to search for axions (left) and dark photons (right) for dark matter. credit: Physical examination letters (2024). DOI: 10.1103/PhysRevLett.132.101001


“Light dark matter candidates behave like waves in the solar medium. Such dark matter waves are predicted to induce very weak oscillating electric fields with magnetic fields due to their negligible interactions with electromagnetism.”

“We focused on detecting the electric field rather than the magnetic field, which is the target signal in most current and proposed experiments,” Ebadi explained.

Light dark matter-induced electric fields can be detected using electro-optical materials, where an external electric field changes the material’s properties, such as the refractive index.

GALILEO uses an asymmetric Michelson interferometer, a device that can measure changes in refractive index. One arm of the interferometer contains the electro-optical material.

When the probe laser beam is split and sent through the two arms of the interferometer, the arm containing the electro-optical material introduces a variable refractive index. This change in refractive index affects the phase of the laser beam, resulting in an oscillating signal when the beams merge back together.

By measuring the differential phase velocity between the two arms of the interferometer, GALILEO can detect the frequency of oscillations caused by bright dark matter. This oscillatory signal serves as a signature for the presence of dark matter particles.

The sensitivity of the method can be increased by including Fabry-Perot cavities (which increase the length of the interferometer arm, allowing greater precision) and making repeated independent measurements.

Laser interferometry and GALILEO implementation

The research relies on precise measurements by laser interferometry.

Ebadi explained: “A prime example of how laser interferometers can be used for precise measurements is LIGO, the ground-based gravitational wave detector.”

“Our proposal uses similar technological advances as LIGO, such as Fabry-Perot cavities or squeezed light to suppress the quantum limit of noise. However, unlike LIGO, the proposed GALILEO interferometer is a bench-scale device.”

Although the work is theoretical, the researchers already have plans to implement the experimental program step by step.

Importantly, they want to determine the technical parameters needed for an optimized experimental setup that they plan to use to conduct scientific experiments to search for bright dark matter.

Furthermore, Ebadi emphasizes the importance of working with high-quality Fabry-Perot cavities together with electro-optical material in the cavity, as well as characterizing the noise budget and setup systematics, which are crucial aspects of the experimental process.

“GALILEO has the potential to be an important component of the larger mission to explore the vast theoretically viable space of dark matter candidates,” concluded Ebadi.

More info:
Reza Ebadi et al, GALILEO: A Galactic Axion Laser Interferometer Using Electro-Optics, Physical examination letters (2024). DOI: 10.1103/PhysRevLett.132.101001.

Log information:
Physical examination letters

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