Speaker
Description
The azimuthal correlation angle, $\Delta\phi$, between the scattered lepton and the leading jet in deep inelastic $ep$ scattering at HERA has been studied using HERA II data collected with the ZEUS detector. Differential cross sections, $d\sigma/d\Delta\phi$, are presented for the first time as a function of the azimuthal correlation angle in various ranges of the jet transverse momentum $p_\mathrm{T,jet}$, photon virtuality $Q^2$ and jet multiplicity. Perturbative calculations at $\mathcal{O}(\alpha_{s}^2)$ accuracy successfully describe the data within the defined fiducial region, while a lower level of agreement is observed near $\Delta\phi \rightarrow \pi$ for events with high jet multiplicity due to limitations of the perturbative approach in describing soft QCD phenomena. Monte Carlo predictions that supplement leading-order matrix elements with parton showering describe the data as well as the $\mathcal{O}(\alpha_{s}^2)$ calculations do.
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