Limits on the effective quark radius from inclusive ep scattering & contact interactions at HERA

TL;DR

This paper uses high-precision HERA data to set new limits on the quark radius and contact interactions, probing potential physics beyond the Standard Model at TeV scales.

Contribution

It introduces a novel simultaneous fitting method for parton distributions and new physics contributions in inclusive ep scattering data.

Findings

Upper limit on effective quark radius: 0.43×10^{-16} cm

Contact interaction mass scale limits extend up to 10 TeV

New analysis approach improves sensitivity to beyond Standard Model physics

Abstract

The high-precision HERA data allow searches for up to TeV scales "Beyond the Standard Model" contributions to electron-quark scattering. Combined H1 and ZEUS measurements of inclusive deep inelastic cross sections in neutral and charged current ep scattering are considered, corresponding to a luminosity of around 1 fb$^{-1}$. A new approach to the beyond the Standard Model analysis of the inclusive $ep$ data is presented; simultaneous fits of parton distribution functions and contributions of "new physics" processes are performed. Considered are possible deviations from the Standard Model due to a finite radius of quarks, described within the quark form-factor model, and due to new electron-quark interactions in the framework of $eeqq$ contact interactions (CI). The resulting 95% C.L. upper limit on the effective quark radius is $0.43\cdot 10^{-16}$ cm. The limits on the CI mass scale extend up to 10 TeV depending on the CI scenario.