Dark Matter Decays Faster In The Milky Way

Researchers in India have proposed a theory to predict the peculiar annihilation behavior of dark matter in the Milky Way.

AsianScientist (July 3, 2017) – Researchers at the Tata Institute of Fundamental Research in Mumbai have proposed a theory that predicts how dark matter may undergo annihilation much more rapidly in the Milky Way compared with smaller or larger galaxies.

In the night sky, only about 20 percent of all the matter in the Universe can be seen. The remaining exists as a non-luminous and exotic form of matter that we know little about. This so-called dark matter has been the object of intense scientific exploration in the last few decades. According to many popular theories, dark matter particles annihilate at the same rate in both small and large astronomical bodies and at all times in the Universe.

The present study published in Physical Review Letters shows that the annihilation rate is not the same everywhere, based on analysis of the tantalizing signals from the Milky Way seen by the PAMELA and AMS02 detector and the Fermi gamma ray telescope. This peculiar behaviour of the annihilation rate stems from the symmetries of the annihilating dark matter particles.

PhD student Mr. Anirban Das and his advisor Dr. Basudeb Dasgupta pursued this possibility because signals arising from dark matter annihilation have rarely been observed anywhere else except in the Milky Way. If the dark matter origin of these signals stands further scrutiny and signals aren’t seen from anywhere except the Milky Way, their theory would explain why the Milky Way appears to be special.

Further, it would predict that dark matter is made of more than one particle and interacts through a yet-undiscovered low-mass particle. The absence of dark matter annihilation signals outside the Milky Way could be a crucial hint towards this richer theory of dark matter, which will be tested by future observations.

The article can be found at: Das & Dasgupta (2017) Selection Rule for Enhanced Dark Matter Annihilation.


Source: Tata Institute of Fundamental Research; Photo: Pexels.
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