BASE's ultra-sensitive detector used in the search for axion-like dark matter
Already from the 1960s onwards, interpretations of analyses of the dynamics of galaxies provided strong indication that there could be about five times more so-called "dark matter" in our Universe in addition to the well-known visible "baryonic" matter. But the microscopic properties of this dark matter are still unknown today. Quantum chromodynamic (QCD) axions and new axion-like particles (ALPs), predicted by extensions to the Standard Model, are excellent dark matter candidates, since they would be produced in the early universe and form a cold dark matter halo consistent with astrophysical observations.
Axions and ALPs couple to two photons, which allows them to convert into photons in a strong external magnetic (or electric)
field. This conversion is the basis for experimental searches for axions and ALPs. The searches are performed in haloscope
experiments (for axions and ALPs in the galactic halo), in helioscope experiments (for solar axions and ALPs) and in purely
laboratory-based experiments. A number of laboratory experiments and astrophysical observations have already placed limits
on ALP masses and couplings in the neV/c2 range.
Besides dedicated axion detectors, ultra-sensitive superconducting single-particle detectors of cryogenic Penning-trap experiments can be repurposed for the detection of axions and ALPs.
In a recent article published in "Physical Review Letters", J. A. Devlin et al. present the results of the investigation of the
ALP-to-photon conversion using the axial detection system of the analysis trap of the
BASE antiproton experiment
at CERN. This analysis
complements the previous BASE study of the possible interactions between ALPs and antiprotons (see our
news of 13.11.19).
BASE is a cryogenic Penning-trap experiment located at CERN's Antimatter Factory, dedicated to testing charge-parity-time-reversal (CPT) invariance by comparing the fundamental properties of protons and antiprotons. BASE allows to detect femtoamp sized image currents induced by oscillating antiprotons inside their analysis trap. The used resonant LC circuit is also sensitive to changes in the magnetic flux, caused by an oscillating ALP field. This allows to extract ALP-photon interaction limits by searching the noise spectrum of the fixed-frequency resonant circuit for peaks caused by hypothetical dark matter ALPs converting into photons in the strong magnetic field (1.945 T) of the Penning-trap magnet.
For a narrow mass range around 2.791 neV, the researchers could place the so far strongest laboratory constraints for
ALP-photon interactions, at a level which is comparable to that obtained from astrophysical observations with the
Fermi-LAT space telescope and stronger than other current haloscope and helioscope experiments.
The new approach opens an avenue for many other Penning-trap experiments to search for ALP signatures. The scientists are considering to adapt the highly sensitive single-particle detectors used in Penning-trap experiments like BASE into more powerful ALP search experiments with higher detection bandwidth.
Please read more in the article ... >
Further press releases:
Limits of atomic nuclei predicted
In a new study, "Ab Initio Limits of Nuclei", published in the journal Physical Review Letters as an Editors' Suggestion
with an accompanying synopsis in APS Physics, our Max Planck Fellow
Professor Achim Schwenk of TU Darmstadt,
together with scientists from the University of Washington, TRIUMF and the
University of Mainz, succeeded in calculating the limits of atomic nuclei using innovative theoretical methods up
to medium-mass nuclei.
The novel calculations have enabled the study of nearly 700 isotopes between helium and iron. The results are a treasure trove of information about possible new isotopes and provide a roadmap for nuclear physicists to verify them.
Further information also in the Synopsis of the article .
Review article on the test of fundamental physics with Penning traps
In Penning traps electromagnetic forces are used to confine charged particles under well-controlled conditions for virtually unlimited time. Sensitive detection methods have been developed to allow observation of single stored ions. Various cooling methods can be employed to reduce the energy of the trapped particle to nearly at rest.
In a recent review article published in Quantum Science and Technology, K. Blaum, S. Eliseev and S. Sturm
summarize how highly charged ions (HCIs) offer unique possibilities for precision measurements in Penning traps.
Precision atomic and nuclear masses as well as magnetic moments of bound electrons allow
among others to determine fundamental constants like the mass of the electron or to perform
stringent tests of fundamental interactions like bound-state quantum electrodynamics.
The authors discuss recent results and future perspectives in high-precision Penning-trap spectroscopy with HCIs.
Please read more in the review article ... >