Search for resonances decaying to \(e^+\)-jet in \(e^+p\) interactions at HERA

Abstract.

The \(e^+\)-jet invariant mass spectrum produced in the reaction \(e^+ p \rightarrow e^+ X\) has been studied at a center-of-mass energy of 300 GeV. The data were collected using the ZEUS detector operating at the HERA collider, and correspond to an integrated luminosity of \(47.7\) pb\(^{-1}\). The observed mass spectrum is in good agreement with Standard Model expectations up to an \(e^+\)-jet mass of \(210\) GeV. Above this mass, some excess is seen. The angular distribution of these events is typical of high-\(Q^2\) neutral current events and does not give convincing evidence for the presence of a narrow scalar or vector state. Limits are presented on the product of cross section and branching ratio for such a state and are interpreted as limits on leptoquark or R-parity-violating squark production. Specific leptoquark types are ruled out at 95% confidence level for coupling strength \(\lambda=0.3\) for masses between 150 and 280 GeV.