  Recent results on light hadron spectroscopy are reported, with special
emphasis on the evidence for a narrow baryonic state decaying to Ks p and Ks
pbar, compatible with the pentaquark state theta^+ observed by fixed target
experiments. The data were collected with the ZEUS detector at HERA using an
integrated luminosity of 121 pb^-1. The analyses were performed in the central
rapidity region of inclusive deep inelastic scattering at an ep centre-of-mass
energy of 300-318 GeV. Evidence for a narrow resonance in the Ks p and Ks pbar
invariant mass spectrum is obtained, with mass 1521.5 \pm
1.5(stat)^{+2.8}_{-1.7}(syst) and width consistent with the experimental
resolution. If the Ks p part of the signal is identified with the strange
pentaquark theta^+, the Ks pbar part is the first evidence for its
antiparticle, thetabar^-. Supporting results on other light hadron resonances
are also discussed.
