Hadronic Final States and Diffraction at HERA

TL;DR

This paper presents recent HERA collider results on jet production and diffraction, testing QCD predictions, refining proton structure models, and exploring the gluonic radius through diffractive processes.

Contribution

It provides new measurements of diffraction and jet production that enhance understanding of proton structure and QCD, including constraints on the gluon distribution and the gluonic radius.

Findings

Jet data improve gluon distribution fits.

Diffractive measurements support factorisation in diffraction.

Gluonic radius of the proton estimated from Upsilon production.

Abstract

Recent results from the ep (electron-proton) collider HERA are presented. Jet production and diffraction type reactions allow tests of predictions of Quantum Chromodynamics (QCD). Jet measurements are used to improve the combined H1-ZEUS parton density fits by adding an additional constraint on the gluon distribution in the proton and, at the same time, providing information on strong coupling constant. Measurements of inclusive diffraction and diffractive dijet data are discussed in the context of factorisation in diffraction. Diffractive Upsilon(1S) production was studied to extract the t-slope of the process, which was found to be consistent with the other exclusive vector meson data and can be interpreted in terms of the gluonic radius of the proton.