The Real Gauge Singlet Scalar Extension of Standard Model: A Possible   Candidate of Cold Dark Matter
  We consider a simplest extension of Standard Model in which a real SM gauge singlet scalar with an additional discrete symmetry $Z_2$ is introduced to SM. This additional scalar can be a viable candidate of cold dark matter since the stability of $S$ is achieved by the application of $Z_2$ symmetry on $S$. Considering $S$ as a possible candidate of cold dark matter we have solved Boltzmann's equation to find the freeze out temperature and relic density of $S$ for Higgs mass 120 GeV in the scalar mass range 5 GeV to 1 TeV. As $HHSS$ coupling $\delta_2$ appearing in Lagrangian depends upon the value of scalar mass $m_S$ and Higgs mass $m_h$, we have constrained the $m_S - \delta_2$ parameter space by using the WMAP limit on the relic density of dark matter in the universe and the results of recent ongoing dark matter direct search experiments namely CDMS-II, CoGeNT, DAMA, EDELWEISS-II, XENON-10, XENON-100. From such analysis we find two distinct mass regions (a lower and higher mass domain) for such a dark matter candidate that satisfy both the WMAP limit and the experimental results considered here. We have estimated the possible differential direct detection rates and annual variation of total detection rates for this scalar dark matter candidate $S$ for two detector materials namely Ge, Xe. Finally we have calculated the $\gamma-$ray flux from the galactic centre due to annihilation of two 130 GeV scalar dark matter into two monoenergetic $\gamma-$rays. 
Anirban Biswas and Debasish Majumdar
hep-ph astro-ph.CO