N. H. Brook

Search for resonance decays to an anti-neutrino plus jet in E + P scattering at DESY HERA

A study of the {anti {nu}}-jet mass spectrum in e{sup +}p{yields}{anti {nu}} X events at a center-of-mass energy 300 GeV has been performed with the ZEUS detector at the HERA collider at DESY using an integrated luminosity of 47.7 pb{sup -1}. The mass spectrum is in good agreement with that expected from standard model processes over the {anti {nu}}-jet mass range studied. No significant excess attributable to the decay of a narrow resonance is observed. By using both e{sup +}p {yields} e{sup +}X and e{sup +}p {yields} {anti {nu}} X data, mass-dependent limits are set on the s-channel production of scalar and vector resonant states. Couplings to first-generation quarks are considered and limits are presented as a function of the e{sup +}q and {anti {nu}} q branching ratios. These limts are used to constrain the production of leptoquarks and R-parity violating squarks.

Measurement of K 0 S , Λ and anti-Λ production at HERA

The production of the neutral strange hadrons K-S(0), Lambda and (Lambda) over bar has been measured in ep collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, Lambda ((Lambda) over bar) asymmetry and polarization have been measured in three kinematic regions: Q(2) > 25 GeV2; 5 < Q(2) < 25 GeV2; and in photoproduction (Q(2) similar or equal to 0). In photoproduction the presence of two hadronic jets, each with at least 5 GeV transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at e(+)e(-) colliders, except for an enhancement of baryon relative to meson production in photoproduction.