The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of $61 \pbi$. The dijet cross section has been measured for virtualities of the exchanged virtual photon, $5 < Q^2 < 100 \gev^2$, and $\gamma^{*} p$ centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive k_{T} algorithm in the $\gamma^* p$ frame, were required to have a transverse energy $E^*_{T, \rm jet} > 4 \gev$ and the jet with the highest transverse energy was required to have $E^*_{T,\rm jet} > 5 \gev$. All jets were required to be in the pseudorapidity range $-3.5 < \eta^*_{\rm jet} < 0$. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data.
Total di-jet cross section SIG as a function of Q**2 .
Distribution of D(SIG)/DQ**2 as a function of Q**2 .
Distribution of D(SIG)/DW as a function of W .
Jet production in deep inelastic scattering for $120<Q~2<3600$GeV$~2$ has been studied using data from an integrated luminosity of 3.2pb$~{-1}$ collected with the ZEUS detector at HERA. Jets are identified with the JADE algorithm. A cut on the angular distribution of parton emission in the $\gamma~*$-parton centre-of-mass system minimises the experimental and theoretical uncertainties in the determination of the jet rates. The jet rates, when compared to ${\cal O}$($\alpha_{s}$~2$) perturbative QCD calculations, allow a precise determination of $\alpha_{s}(Q)$ in three $Q~2$-intervals. The values are consistent with a running of $\alpha_{s}(Q)$, as expected from QCD. Extrapolating to $Q=M_{Z~0}$ yields $\alpha_{s}(M_{Z~0}) = 0.117\pm0.005(stat)~{+0.004}_{-0.005}(syst_{exp}) {\pm0.007}(syst_{theory})$.
2+1 jet rate as a function of ycut the jet algorithm cut-off value. Statistical errors only.
Measured values of Lambda-QCD in the MS Bar scheme and alpha_s as a function of Q**2. The second systematic uncertainty is related to the theoretical uncertainties .
Strong coupling constant alpha_s extrapolated to the Z0 mass.
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