Search for pentaquarks decaying to Ξπ in deep inelastic scattering at HERA

A search for pentaquarks decaying to Ξ−π− (Ξ−π+) and corresponding antiparticles has been performed with the ZEUS detector at HERA. The data sample consists of deep inelastic ep scattering events at centre-of-mass energies of 300 and 318 GeV, and corresponds to 121 pb−1 of integrated luminosity. A clear signal for Ξ0(1530)→Ξ−π+ was observed. However, no signal for any new baryonic state was observed at higher masses in either the Ξ−π− or Ξ−π+ channels. The searches in the antiparticle channels were also negative. Upper limits on the ratio of a possible Ξ3/2−− (Ξ3/20) signal to the Ξ0(1530) signal were set in the mass range 1650-2350 MeV.