Search for Contact Interactions in e^{\pm}p Collisions at HERA

TL;DR

This study searches for signs of physics beyond the Standard Model in high-Q^2 neutral current deep inelastic scattering at HERA, finding no deviations but setting new limits on various theoretical models including contact interactions, leptoquarks, supersymmetry, and extra dimensions.

Contribution

It provides the first comprehensive set of experimental limits on new physics models at high Q^2 using the full H1 data sample, extending previous bounds significantly.

Findings

No significant deviation from the Standard Model observed.

Lower limits on compositeness scale Lambda range from 3.6 to 7.2 TeV.

Constraints on leptoquark masses and couplings, and on models with extra dimensions.

Abstract

A search for physics beyond the Standard Model in neutral current deep inelastic scattering at high negative four-momentum transfer squared Q^2 is performed in e^{\pm}p collisions at HERA. The differential cross section ds/dQ^2, measured using the full H1 data sample corresponding to an integrated luminosity of 446 pb^{-1}, is compared to the Standard Model prediction. No significant deviation is observed. Limits on various models predicting new phenomena at high Q^2 are derived. For general four-fermion eeqq contact interaction models, lower limits on the compositeness scale Lambda are set in the range 3.6 TeV to 7.2 TeV. Leptoquarks with masses M_{LQ} and couplings lambda are constrained to M_{LQ}/lambda > 0.41-1.86 TeV and limits on squarks in R-parity violating supersymmetric models are derived. A lower limit on the gravitational scale in (4+n) dimensions of M_{S} > 0.9 TeV is established for low-scale quantum gravity effects in models with large extra dimensions. For the light quark radius an upper bound of R_q< 0.65 10^{-18} m is determined.