Context: In a recently published paper by Raman Research Institute (RRI), an autonomous institute of the Department of science and Technology (DST), they confirmed the relevance of Weakly Interacting Massive Particles (WIMP) by relaxing certain earlier assumptions and hence proved that theorizing dark matter from particle physics was possible.
Dark Matter
About 80% of the matter in the universe cannot be observed through telescopes due to instrument limitations. This is due to its weak interaction with the electromagnetic waves which are used by scientists to map the universe. Because of this particular reason this part of the universe is invisible to human eyes and termed as ‘Dark Matter’.
Despite being invisible, the presence of dark matter can be detected through its gravitational influence, evident in the orbital speed of stars around galaxies and the movements of clusters of galaxies. But this matter’s true nature and interaction with other matters remains undefined.
Cold Dark Matter (CDM)
Out of this dark matter, 25% is identified as cold dark matter.
- This differentiation of dark matter is done on the basis of the mass of dark matter particles and they are categorised as "cold" or "hot."
- According to the standard model for dark matter, Lower-mass particles are considered "warmer" and move faster and if particles are "cold," it means they move slowly compared to the speed of light and have higher mass.
- To unravel this mystery, extensive research is ongoing. Many scientists believe that the discovery of new kinds of subatomic particles, fundamentally different from those composing ordinary matter, will lead to a resolution.
Weakly Interacting Massive Particles (WIMP)
WIMPs represent one hypothesised class of particles to explain dark matter.
- They neither absorb nor emit light and have weak interactions with other particles. However, when WIMPs encounter each other, they annihilate, producing gamma rays.
- Such particles arises naturally in extensions of the standard model of particle physics and predict the correct energy density of the Cold Dark Matter for plausible range of interaction strength (WIMP miracle).
- However, in spite of intensive searches and orders of magnitude improvement in the sensitivity of lab experiments (e.g. Xenon based experiments), WIMP has not yet been detected.