Chasing the WIMPs of Milky Way: Direct Detection of Dark Matter

A variety of astronomical observations indicate that the dominant
component of the mass density of the Universe is in a form that emits
no detectable electromagnetic radiation. What constitutes this “Dark
Matter” (DM) is unknown, and remains one of the major unsolved
problems of fundamental physics. One of the most favored candidates
for DM is some kind of Weakly Interacting Massive Particles (WIMPs)
with mass anywhere in the region of a few GeV to several TeV predicted
in many models of Particles Physics beyond the Standard Model. Several
experiments worldwide are currently trying to detect these
hypothetical WIMPs directly through detection of nuclear recoils due
to scattering of WIMPs off nuclei of suitably chosen detector
materials in low background underground facilities, and indirectly
through detection of the expected gamma rays and neutrinos from the
annihilation of these WIMPs accumulated in the core of the Sun and in
other high density regions such as the Galactic Centre.  In this
Colloquium, we focus on WIMP direct detection efforts. After giving an
overview of the basic ideas involved, we discuss the current status of
the results from some of the major direct detection experiments,
highlighting the latest results from the PICASSO experiment currently
underway at the SNOLab underground facility in Sudbury, Canada, in
which Saha Institute, Kolkata, is involved. Finally, recent efforts
towards setting up a cryogenic, Silicon-based, Dark Matter search
experiment in India will be discussed.