Scientists are sure dark matter exists. Yet, after more than 50 years of research, they still have no direct evidence for the mysterious substance.
Swati Singh, of the University of Delaware, is one of a small group of researchers in the dark matter community who have begun to question whether they are looking for the right kind of dark matter.
“What if dark matter was much lighter than what traditional particle physics experiments look for?” said Singh, assistant professor of electrical and computer engineering at UD.
Now Singh, UD doctoral student Jack Manley, and collaborators from the University of Arizona and Haverford College have come up with a new way to search for particles that could make up dark matter by reusing technology from existing table sensor. The team recently reported their approach in an article published in Physical examination letters.
The co-authors of the article include Dalziel Wilson, assistant professor of optics in Arizona, Mitul Dey Chowdhury, doctoral student in Arizona, and Daniel Grin, assistant professor of physics at Haverford College.
No ordinary subject
Singh explained that if you add up all the things that emit light, such as stars, planets, and interstellar gas, that is only about 15% of the matter in the Universe. The remaining 85% is known as dark matter. It doesn’t emit light, but researchers know it exists through its gravitational effects. They also know that it is not ordinary matter, like gas, dust, stars, planets, and us.
“It could be made up of black holes or something trillions of times smaller than an electron, known as ultralight dark matter,” said Singh, a quantum theorist known for her pioneering efforts to advance science. mechanical detection of dark matter. .
One possibility is that dark matter is made up of dark photons, a type of dark matter that would exert a weak oscillating force on normal matter, causing a particle to move back and forth. However, since dark matter is everywhere, it exerts this force on everything, making it difficult to measure this movement.
Singh and colleagues said they believe they can overcome this obstacle by using optomechanical accelerometers as sensors to detect and amplify this oscillation.
“If the force depends on the material, using two objects made of different materials, the amount of force they are forced will be different, which means you would be able to measure this difference in acceleration between the two materials,” said Manley, head of the author journal.
Wilson, a quantum experimenter and one of the collaborators of the UD team, compared an optomechanical accelerometer to a miniature tuning fork. “It is a vibrating device which, due to its small size, is very sensitive to environmental disturbances,” he said.
Now the researchers have proposed an experiment using a silicon nitride membrane and a fixed beryllium mirror to bounce light between the two surfaces. If the distance between the two materials changes, the researchers would know from the reflected light that dark photons were present because silicon nitride and beryllium have different material properties.
Collaboration was a key part of developing the design of the experiment, according to Manley. He and Singh (theorists) worked with Wilson and Dey Chowdhury (experimenters) on the theoretical calculations that went into the blueprint for building their proposed tabletop accelerometer sensor. Meanwhile, Grin, a cosmologist, helped shed light on aspects of particle physics of ultralight dark matter, such as why it would be ultralight, why it might couple differently to materials, and how it might be produced. .
As a theorist, Manley said the opportunity to learn more about how devices work and how experimenters build things to prove the theories developed by him and Singh deepened his expertise while simultaneously expanding his exposure. to possible career paths.
More and more important work
It is important to note that this latest work is based on research previously published by the collaborating teams, reported last summer in Physical examination letters. The paper, which included contributions from former UD graduate student Russell Stump, showed that several existing, near-term lab-scale devices are sensitive enough to detect, or rule out, possible particles that could be ultralight dark matter.
Research has reported that certain types of ultralight dark matter will connect or couple with normal matter in a way that causes atoms to change periodically. While small fluctuations in the size of a single atom may be difficult to notice, the effect is amplified in an object composed of many atoms, and additional amplification can be achieved if that object is an acoustic resonator. The collaboration evaluated the performance of several resonators made of various materials ranging from superfluid helium to single crystal sapphire, and found that these sensors can be used to detect this dark matter-induced distortion signal.
Both projects were supported in part with funding from Singh of the National Science Foundation to explore emerging ideas around the use of advanced quantum devices to detect astrophysical phenomena with tabletop technologies that are smaller and less expensive. than other methods.
Together, Singh said, these papers expand the body of work on what is known about possible ways to detect dark matter and suggest the possibility of a new generation of tabletop experiments.
Singh and Manley are also working with other experimental groups to develop additional tabletop sensors to search for such dark matter or other weak astrophysical signals. They are also actively engaged in broader discussions on this topic within dark matter and quantum sensor communities.
For example, Singh recently discussed advances in transformational instrumentation in particle physics detectors at a virtual workshop hosted by the Department of Energy’s Advanced Detector Coordination Panel (CPAD). She also presented these results in a special workshop at the April meeting of the American Physical Society.
“This is an exciting time and I am learning a lot from the questions asked by scientists from diverse backgrounds at such workshops,” Singh said. “But it’s interesting that my most original research ideas still come from questions asked by curious students.”