Comparison of ZEUS Data with Standard Model Predictions for e\u3csup\u3e+\u3c/sup\u3ep → e\u3csup\u3e+\u3c/sup\u3ex Scattering at High X and Q\u3csup\u3e2\u3c/sup\u3e

Abstract

Using the ZEUS detector at HERA, we have studied the reaction e+p → e+X for Q2 \u3e 5000 GeV2 with a 20.1 pb-1 data sample collected during the years 1994 to 1996. For Q2 below 15000 GeV2, the data are in good agreement with Standard Model expectations. For Q2 \u3e 35000 GeV2, two events are observed while 0.145 ± 0.013 events are expected. A statistical analysis of a large ensemble of simulated Standard Model experiments indicates that with probability 6.0%, an excess at least as unlikely as that observed would occur above some Q2 cut. For x \u3e 0.55 and y \u3e 0.25, four events are observed where 0.91 ± 0.08 events are expected. A statistical analysis of the two-dimensional distribution of the events in x and y yields a probability of 0.72% for the region x \u3e 0.55 and y \u3e 0.25 and a probability of 7.8% for the entire Q2 \u3e 5000 GeV2 data sample. The observed excess above Standard Model expectations is particularly interesting because it occurs in a previously unexplored kinematic region. © Springer-Verlag 1997