Study of finite temperature QCD with 2+1 flavors via Taylor expansion and imaginary chemical potential

We study QCD with 2+1 flavors at nonzero temperature and nonzero chemical potential. We present preliminary results obtained from lattice calculations performed with an improved staggered fermions action (p4-action) on lattice with temporal extent N_t = 4 on a line of constant physics with the strange quark mass adjusted to its physical value and a pion mass of about 220 MeV. We compute at imaginary chemical potential and compare with Taylor expansion results. We focus our study on a range of temperatures 0.94 < T/T_c < 1.08.