Direct detection of WIMPs : Implications of a self-consistent truncated
  isothermal model of the Milky Way's dark matter halo
  Direct detection of Weakly Interacting Massive Particle (WIMP) candidates of
Dark Matter (DM) is studied within the context of a self-consistent truncated
isothermal model of the finite-size dark halo of the Galaxy based on the "King
model" of the phase space distribution function of collisionless DM particles.
Our halo model takes into account the modifications of the phase-space
structure of the halo due to the gravitational influence of the observed
visible matter in a self-consistent manner. The parameters of the halo model
are determined by a fit to a recently determined circular rotation curve of the
Galaxy that extends up to $\sim$ 60 kpc. Unlike in the Standard Halo Model
(SHM) customarily used in the analysis of the results of WIMP direct detection
experiments, the velocity distribution of the WIMPs in our model is
non-Maxwellian with a cut-off at a maximum velocity that is self-consistently
determined by the model itself. For our halo model that provides the best fit
to the rotation curve data, the 90% C.L. upper limit on the WIMP-nucleon
spin-independent cross section from the recent results of the CDMS-II
experiment, for example, is $\sim 5.3\times10^{-8}\pb$ at a WIMP mass of $\sim$
71 GeV. We also find, using the original 2-bin annual modulation amplitude data
of the DAMA experiment, that there exists a range of small WIMP masses,
typically $\sim$ 2 -- 16 GeV, within which DAMA collaboration's claimed annual
modulation signal purportedly due to WIMPs is compatible with the null results
of other experiments. These results strengthen the possibility of low-mass
($\lsim 10\gev$) WIMPs as a candidate for dark matter as indicated by several
earlier studies performed within the context of the SHM. A more rigorous
analysis using DAMA bins over smaller intervals should be able to better
constrain the "DAMA regions" in the WIMP parameter space within the context of
our model.
