Search for contact interactions, large extra dimensions and finite quark radius in ep collisions at HERA

TL;DR

This study analyzed high-Q^2 deep inelastic scattering data from HERA to search for signs of physics beyond the Standard Model, including contact interactions, extra dimensions, and finite quark size, finding no deviations but setting new limits.

Contribution

The paper provides the first limits on contact interactions, large extra dimensions, and quark radius using HERA data at high Q^2, extending previous constraints.

Findings

No significant deviations from the Standard Model observed.

Limits set on effective mass scale in contact interactions.

Quark charge radius constrained to 0.85×10^-16 cm.

Abstract

A search for physics beyond the Standard Model has been performed with high-Q^2 neutral current deep inelastic scattering events recorded with the ZEUS detector at HERA. Two data sets, e^+ p \to e^+ X and e^- p \to e^- X, with respective integrated luminosities of 112 pb^-1 and 16 pb^-1, were analyzed. The data reach Q^2 values as high as 40000 GeV^2. No significant deviations from Standard Model predictions were observed. Limits were derived on the effective mass scale in eeqq contact interactions, the ratio of leptoquark mass to the Yukawa coupling for heavy leptoquark models and the mass scale parameter in models with large extra dimensions. The limit on the quark charge radius, in the classical form factor approximation, is 0.85 10^-16 cm.