  We investigate three-nucleon forces (3NF) from lattice QCD simulations,
utilizing the Nambu-Bethe-Salpeter (NBS) wave function to determine two-nucleon
forces (2NF) and 3NF on the same footing. Quantum numbers of the three-nucleon
(3N) system are chosen to be (I, J^P)=(1/2, 1/2^+) (the triton channel). We
consider the simplest geometrical configuration where 3N are aligned linearly
with an equal spacing, to reduce the enormous computational cost. Lattice QCD
simulations are performed using Nf=2 dynamical clover fermion configurations at
the lattice spacing of a = 0.156 fm on a 16^3 x 32 lattice with a large quark
mass corresponding to m(\pi) = 1.13 GeV. We find repulsive 3NF at short
distance.

High Energy Physics - Lattice;High Energy Physics - Phenomenology;Nuclear Theory