  Cosmic Microwave Background (CMB) is a powerful probe to study the early
universe and various cosmological models. Weak gravitational lensing affects
the CMB by changing its power spectrum, but meanwhile, it also carries
information about the distribution of lensing mass and hence, the large scale
structure (LSS) of the universe. When studies of the CMB is combined with the
tracers of LSS, one can constrain cosmological models, models of LSS
development and astrophysical parameters simultaneously. The main focus of this
project is to study the cross-correlations between CMB lensing and the galaxy
matter density to constrain the galaxy bias ($b$) and the amplitude scaling
parameter ($A$), to test the validity of $\Lambda$CDM model. We test our
approach for simulations of the Planck CMB convergence field and galaxy density
field, which mimics the density field of the Herschel Extragalactic Legacy
Project (HELP). We use maximum likelihood method to constrain the parameters.
