  ND and ND^* interactions become a hot topic after the observation of new
charmed hadrons \Sigma_c(2800) and \Lambda_c(2940)^+. In this letter, we have
preliminary investigated S-wave ND and ND^* interactions with possible quantum
numbers in the chiral SU(3) quark model and the extended chiral SU(3) quark
model by solving the resonating group method equation. The numerical results
show that the interactions between N and D or N and D^* are both attractive,
which are mainly from \sigma exchanges between light quarks. Further
bound-state studies indicate the attractions are strong enough to form ND or
ND^* molecules, except for (ND)_{J=3/2} and (ND^*)_{J=3/2} in the chiral SU(3)
quark model. In consequence ND system with J=1/2 and ND^* system with J=3/2 in
the extended SU(3) quark model could correspond to the observed \Sigma_c(2800)
and \Lambda_c(2940)^+, respectively. Naturally, the same method can be applied
to research NB and NB^* interactions, and similar conclusions obtained, i.e. NB
and NB^* attractive forces may achieve bound states, except for (NB^*)_{J=3/2}
in the chiral SU(3) quark model. Meanwhile, S partial wave phase shifts of
ND^{(*)} and NB^{(*)} elastic scattering are illustrated, which are
qualitatively consistent with results from bound state problem.
