We present the results of a lattice study of light-cone distribution
amplitudes (DAs) of the nucleon and negative parity nucleon resonances using
two flavors of dynamical (clover) fermions on lattices of different volumes and
pion masses down to m_pi = 150 MeV. We find that the three valence quarks in
the proton share their momentum in the proportion 37% : 31% : 31%, where the
larger fraction corresponds to the u-quark that carries proton helicity, and
determine the value of the wave function at the origin in position space, which
turns out to be small compared to the existing estimates based on QCD sum
rules. Higher-order moments are constrained by our data and are all compatible
with zero within our uncertainties. We also calculate the normalization
constants of the higher-twist DAs that are related to the distribution of quark
angular momentum. Furthermore, we use the variational method and customized
parity projection operators to study the states with negative parity. In this
way we are able to separate the contributions of the two lowest states that, as
we argue, possibly correspond to N*(1535) and a mixture of N*(1650) and the
pion-nucleon continuum, respectively. It turns out that the state that we
identify with N*(1535) has a very different DA as compared to both the second
observed negative parity state and the nucleon, which may explain the
difference in the decay patterns of N*(1535) and N*(1650) observed in
experiment.Comment: 19 pages, 11 figure
