S, T, and Leptoquarks at HERA

Abstract

If the recently discovered anomalous events at HERA are due to a scalar leptoquark, then it is very likely to have weak isospin $I=1/2$. In that case, present precision measurements of the oblique radiative parameters $S$ and $T$ provide strong constraints on the mass of the other component of this doublet. If the standard model is extended to include such a doublet, a slightly better fit may in fact be obtained. However, in specific proposed models where this doublet comes from a larger symmetry, there are often additional large and positive contributions to $S$ from exotic heavy fermions which far exceed the present experimental limit. A way to improve the Tevatron exploration of leptoquarks is proposed.

10 pages including 3 figures

References in corpus (3)

• Comparison of ZEUS Data with Standard Model Predictions for e^+ p -> e^+ X Scattering at High x and Q^2
• Observation of Events at Very High Q^2 in ep Collisions at HERA
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