Narrow Results

The nonlinear behavior in electron–nucleus collisions for nuclei with mass number $A=56,108,208$ and 265 at very small $x$ regime $(1E-8<x<0.1)$ with low and moderate $Q^2$ is studied. The charm and bottom heavy quarks contributions to the reduced cross-section and ratio of structure functions $F_L^{H-A}$ to $F_2^{H-A}$ are investigated by using the Kharzeev–Levin–Nardi phenomenological ansatz at LO and NLO analyses.

Multi-jet production has been investigated at HERA using the ZEUS detector. Three- and four-jet final states have been measured¹ in photoproduction (PHP). The three- and four-jet cross sections have been compared with two leading-logarithm parton-shower Monte Carlo models, with and without multi-parton interactions. Two- and three-jet production in deep inelastic (DIS) ep scattering has been measured² for 10 < Q² < 100 GeV² in the region of small Bjorken x (10^-4 < x_Bj < 10^-2) and compared to the predictions based on next-to-leading-order QCD calculations. In the third analysis³ described here, angular correlations between the jets and the proton beam direction were investigated in three-jet production in DIS to separate the contributions from the different color configurations. The measurements are compared to fixed-order perturbative calculations assuming the values of the color factors C_F, C_A and T_F as derived from a variety of gauge groups. The photoproduction analysis used a data sample with a luminosity of 121 pb^-1. Both DIS analyses used 82 pb^-1. Jets were reconstructed with the k_T cluster algorithm in the longitudinally invariant inclusive mode.