  We aim to construct quark hadron physics based on QCD. First, using lattice
QCD, we study mass spectra of positive-parity and negative-parity baryons in
the octet, the decuplet and the singlet representations of the SU(3) flavor. In
particular, we consider the lightest negative-parity baryon, the
$\Lambda$(1405), which can be an exotic hadron as the $N \bar K$ molecular
state or the flavor-singlet three-quark state. We investigate the
negative-parity flavor-singlet three-quark state in lattice QCD using the
quenched approximation, where the dynamical quark-anitiquark pair creation is
absent and no mixing occurs between the three-quark and the five-quark states.
Our lattice QCD analysis suggests that the flavor-singlet three-quark state is
so heavy that the $\Lambda$(1405) cannot be identified as the three-quark
state, which supports the possibility of the molecular-state picture of the
$\Lambda$(1405). Second, we study thermal properties of the scalar glueball in
an anisotropic lattice QCD, and find about 300 MeV mass reduction near the QCD
critical temperature from the pole-mass analysis. Finally, we study the
three-quark potential, which is responsible to the baryon properties. The
detailed lattice QCD analysis for the 3Q potential indicates the Y-type
flux-tube formation linking the three quarks.
