Search for resonance decays to a $\overline{\nu }$ plus jet in $e^{+}p$ scattering at DESY HERA

A study of the $\overline{\nu }$-jet mass spectrum in $e^{+}\overrightarrow{p}\overline{\nu }X$ 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 ${\mathrm{pb}}^{-1}.$ The mass spectrum is in good agreement with that expected from standard model processes over the $\overline{\nu }$-jet mass range studied. No significant excess attributable to the decay of a narrow resonance is observed. By using both $e^{+}\overrightarrow{p}{e}^{+}X$ and $e^{+}\overrightarrow{p}\overline{\nu }X$ 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 $e^{+}q$ and $\overline{\nu }q$ branching ratios. These limits are used to constrain the production of leptoquarks and R-parity violating squarks.