Dark matter mystery intensifies over consistent detection of its signal

cosine100 dark matter detector
Cosine100 dark matter detector.(Credit:Chang Hyon Ha)

Dark matter is one of the Universe’s greatest mysteries. Something is out there generating the gravitational force that can’t be accounted for by detectable matter. The way the stars and galaxies move indicates that up to 85 percent of the matter in the Universe is actually dark matter.

There were many experiments which were carried out in order to understand the dark matter. The researchers are trying hard in order to find out the details about the dark matter as it can answer many unanswered questions about the big bang theory and formation of the universe itself.

The DAMA experiment which was carried out in Italy which included detection of dark matter using the direct detection approach, by using a matrix of NaI(Tl) scintillation detectors to detect dark matter particles in the galactic halo. This experiment has further confirmed the presence of a model-independent annual modulation effect of the data in the 2-6 keV range that satisfy all the features expected for a dark matter signal with high statistical significance.

There are two experiments which are carried out in order to verify the above results. However, ANAIS, a dark matter detector run by the University of Zaragoza at the Canfranc Underground Laboratory in Spain, has delivered results that seem to contradict DAMA‘s.

COSINE-100, run by a collaboration between the Korea Invisible Mass Search and Yale University at the Yangyang Underground Laboratory in South Korea, has now produced new output. These results are similar to what ANAIS’ threw up – but also a little closer to the results DAMA has produced over the last 20 years.

That latest COSINE-100 report also comes after an announcement just a few months ago that the collaboration’s results did not support DAMA’s dark matter findings.

DAMA has been recording WIMP (Weakly interacting massive particles) detections since 1995, observed as an annual fluctuation in the number of light flashes detected.

Because of the orbit of Earth around the Sun, and the Solar System’s orbit around the galactic centre, Earth should theoretically be exposed to dark matter flux from the galactic halo around peaking at around 2 June and ebbing at around 2 December.

This is because the faster we are moving through space, the more dark matter should pound us, and mid-year is when the orbital speeds of Earth and the Solar System combined.

Xenon Dark Matter Detector
A tank filled with liquid xenon deep underground to spot dark matter particles

This is exactly what DAMA scientists claim their results show, but no other dark matter detector has come close to replicating it – not even XENON1T which is hailed as our best shot at finding the elusive stuff.

However, XENON1T uses liquid xenon detectors. Meanwhile, DAMA uses sodium iodide crystal detectors in a tank filled with a liquid scintillator to tag cosmic ray muons. This is what ANAIS and COSINE-100 did, but they still didn’t even get close to DAMA results.

It’s probably going to take a few more years of observations before physicists are any closer to unveiling the truth.

We are truly waiting for the final conclusion which would probably open up some secrets of the universe.


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