We study the equation of state in two-flavor QCD at finite temperature and
density. Simulations are made with the RG-improved gluon action and the
clover-improved Wilson quark action. Along the lines of constant physics for
mPS​/mV​=0.65 and 0.80, we compute the derivatives of the quark
determinant with respect to the quark chemical potential μq​ up to the
fourth order at μq​=0. We adopt several improvement techniques in the
evaluation. We study thermodynamic quantities and quark number susceptibilities
at finite μq​ using these derivatives. We find enhancement of the quark
number susceptibility at finite μq​, in accordance with previous
observations using staggered-type quarks. This suggests the existence of a
nearby critical point.Comment: 7 pages, 16 figures, presented at the XXVI International Symposium on
Lattice Field Theory (LATTICE 2008), July 14-19, 2008, Williamsburg,
Virginia, US