Axions are theoretical lightweight particles that may address two major puzzles in physics: they could explain why certain nuclear interactions preserve time symmetry and may also make up dark matter. Dark matter itself does not emit, reflect, or absorb light and has yet to be directly detected.
Axions are extremely light, hypothetical particles believed to have formed in the early universe and to still exist today. They interact very weakly with normal matter but can convert into photons in strong magnetic fields.
The QUAX (Quest for Axions / QUaerere AXion) collaboration is a large team of researchers from several institutes across Italy, created to search for axions using two haloscopes located at the Laboratori Nazionali di Legnaro (LNL) and the Laboratori Nazionali di Frascati (LNF).
Latest Results from QUAX’s Dark Matter Axion Search
In a study published in Physical Review Letters, the team presents results from their latest dark matter axion search, which uses a microwave cavity placed in a strong magnetic field to probe the axion–photon interaction.
“Our work continues the INFN (Istituto Nazionale di Fisica Nucleare) research program on axions, which has been ongoing since 2015,” said Giosuè Sardo Infirri and Pino Ruoso of the QUAX collaboration in an interview with Phys.org.
Our objective is to develop a high-frequency haloscope—operating above 10 GHz—with sensitivity capable of probing theoretically well-motivated models. This paper represents the latest major milestone toward achieving that goal.
“The drive to search for axions stems from the central importance of the dark matter problem in modern physics, as well as the fact that axions are among the most compelling dark matter candidates.”
A Ten-Year Effort to Detect Axions Using Haloscopes
Because the mass of the axion is unknown, experiments searching for it must be able to scan a broad range of possible masses. QUAX’s recent work focuses on exploring a previously untested high-mass region.
Their setup achieves extremely high sensitivity, enabling the investigation of axion masses above 40 microelectronvolts—a range that has gained attention due to recent theoretical developments. Haloscopes, used in these searches, convert axions into measurable photons and detect the resulting signals.
“The QUAX collaboration searches for power generated by the interaction between axions and virtual photons produced by the magnetic field,” Sardo Infirri and Ruoso explained.
“The expected signal appears as an extremely faint excess of power at an unknown frequency, emerging above the background noise. To observe such a weak effect, we place a copper cavity inside a strong magnetic field.”
Within this magnetized copper cavity, axions produce a tiny power surplus as they convert into real photons. This tiny signal can be detected with a coupled antenna and a quantum-limited amplifier. To cover different possible axion masses, the detection setup operates across a broad range of frequencies.
“Changing the cavity opening alters its resonant frequency and the detectable axion mass,” the researchers explained. “For each cavity configuration, we can then compare pure noise with the potential presence of a signal.”
Search Results and Plans for Future Studies
The QUAX collaboration has not yet detected any signals consistent with axions converting into photons. Their recent experiments show their partially automated system can tune across frequencies, highlighting its potential to detect axion-photon conversions.
“Our initial search lays the groundwork for a haloscope capable of operating autonomously at high frequencies,” said Sardo Infirri and Ruoso.
“We have adapted the haloscope to higher frequencies, opening up a new range of axion masses to investigate. This search is crucial: finding an axion would confirm dark matter, while not finding one would rule out some theoretical models.
The QUAX collaboration is preparing the next round of axion searches using their haloscopes at LNL and LNF. In upcoming experiments, they aim to boost haloscope sensitivity and explore a wider range of axion masses.
“In our next experiments, we also plan to expand the search region as much as possible by using additional and improved cavities,” Sardo Infirri and Ruoso added.
“We also hope to fully automate the system so it can run and collect data on its own.”
Read the original article on: Phys.Org
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