Multijet production in neutral current deep inelastic scattering at HERA and determination of α_{s}

Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson virtualities 10 5 GeV and –1 < η_{LAB}^{jet} < 2.5. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant α_{s} (M_{z}), determined from the ratio of the trijet to dijet cross sections, is α_{s} (M_{z}) = 0.1179 ± 0.0013 (stat.)_{-0.0046}^{+0.0028}(exp.)_{-0.0046}^{+0.0028}(th.)

Measurement of open beauty production at HERA in the D *μ final state

The production of beauty quarks with a D*± and a muon in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb-1. Low transverse-momentum thresholds for the muon and D* meson allow for a measurement of beauty production closer to the production threshold than previous measurements. The beauty signal was extracted using the charge correlations and angular distributions of the muon with respect to the D* meson. Cross sections for photoproduction and deep inelastic scattering are somewhat higher than, but compatible with, next-to-leading-order QCD predictions, and compatible with other measurements. © Springer-Verlag Berlin Heidelberg 2007

Measurement of high-Q**2 deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA.

The cross sections for charged and neutral current deep inelastic scattering in e + p collisions with a longitudinally polarised positron beam have been measured using the ZEUS detector at HERA. The results, based on data corresponding to an integrated luminosity of 23.8 pb -1 at sqrt(s) = 318 GeV, are given for both e + p charged current and neutral current deep inelastic scattering for both positive and negative values of the longitudinal polarisation of the positron beam. Single differential cross sections are presented for the kinematic region Q 2 > 200 GeV 2. The measured cross sections are compared to the predictions of the Standard Model. A fit to the data yields σ CC ( P e = - 1 ) = 7.4 ± 3.9 ( stat. ) ± 1.2 ( syst. ) pb, which is consistent within two standard deviations with the absence of right-handed charged currents in the Standard Model