Much of the hunt for dark matter thus far has focused on so-called weakly interacting massive particles, or WIMPs. There was very good theoretical reason to focus on that mass range, most notably the concept of supersymmetry, whereby every particle in the Standard Model should have a "super-partner" that is heavier and in the opposite class (fermion or boson).
The downside is that they interact even more weakly with regular matter than WIMPS, so they cannot be produced in large colliders—one current method for detecting WIMPs. Physicists don't know what the axion's mass might be, so there's a broad parameter space in which to search, and no single instrument can cover all of it, according to co-author Matthew Lawson, also a postdoc at Stockholm University.
That includes experiments—most notably ADMX and HAYSTAC—that employ resonate cavity haloscopes, instruments that use a strong magnetic field to convert dark matter axions to detectable microwave photons.
For a Galton board with any given number of rows, the number of different paths a marble can take to reach a bin placed at a given row is exactly equal to the corresponding number in Pascal’s triangle (as shown below).
In a traditional Galton board, the marble distribution in every row is highest in the center and falls off toward the ends.
In a traditional Galton board, the final position of an individual marble as it moves from about the middle row to the bottom is not very predictable — it could end up in any of the bins.
It’s as if the universe splits every time a marble goes left or right in a Galton board, just because we are ignorant of the exact details of the marble-peg interaction.
According to recent neutrino oscillation data (which reveals the differences between the mass states rather than their actual values), if the lightest mass state is zero, the heaviest must be at least 0.0495 eV.
While neutrino oscillation experiments have measured the differences between the mass states, experiments like KATRIN home in on a kind of average of the three.
But this indirect method hinges on the assumption that models of the cosmos are correct, so if it gives a different answer than direct measurements of the neutrino mass, this might indicate that cosmological theories are wrong.
If, on the other hand, the neutrino mass is close to what cosmological observations predict, KATRIN won’t be sensitive enough to measure it.
If neutrinos are lighter than that, physicists will need more sensitive experiments to close in on its mass and resolve the particle physics and cosmology questions.