Search for new physics in e^\pm q contact interactions at HERA

TL;DR

This paper uses high-Q^2 deep-inelastic scattering data from HERA to search for signs of new physics beyond the Standard Model, setting limits on contact interactions, leptoquarks, supersymmetry, and extra dimensions.

Contribution

It provides the first constraints on various new physics scenarios using HERA data at high momentum transfer.

Findings

Lower limits on compositeness scales between 1.6 and 5.5 TeV.

Constraints on leptoquark and squark masses over lambda > 0.3-1.4 TeV.

Limits on the effective Planck scale in extra dimension models > 0.8 TeV.

Abstract

Deep-inelastic e^\pm p scattering at high squared momentum transfer Q^2 up to 30000 GeV^2 is used to search for eq contact interactions associated to scales far beyond the HERA centre of mass energy. The neutral current cross section measurements d sigma / d Q^2, corresponding to integrated luminosities of 16.4 pb^-1 of e^- p data and 100.8 pb^-1 of e^+ p data, are well described by the Standard Model and are analysed to set constraints on new phenomena. For conventional contact interactions lower limits are set on compositeness scales Lambda ranging between 1.6 - 5.5 TeV. Couplings and masses of leptoquarks and squarks in R-parity violating supersymmetry are constrained to M / lambda > 0.3 - 1.4 TeV. A search for low scale quantum gravity effects in models with large extra dimensions provides limits on the effective Planck scale of M_S > 0.8 TeV. A form factor analysis yields a bound on the radius of light quarks of R_q < 1.0 x 10^-18 m.