Abstract
For the first time, differential inclusive-jet cross sections have been measured in neutral current deep inelastic ep scattering using the anti-kT and SIScone algorithms. The measurements were made for boson virtualities Q2>125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 82 pb−1 and the jets were identified in the Breit frame. The performance and suitability of the jet algorithms for their use in hadron-like reactions were investigated by comparing the measurements to those performed with the kT algorithm. Next-to-leading-order QCD calculations give a good description of the measurements. Measurements of the ratios of cross sections using different jet algorithms are also presented; the measured ratios are well described by calculations including up to O(αs3) terms. Values of αs(MZ) were extracted from the data; the results are compatible with and have similar precision to the value extracted from the kT analysis.
Highlights
Jet production at high transverse energies in neutral-current (NC) deep inelastic ep scattering (DIS) at HERA provides unique tests of perturbative QCD in a cleaner hadron-like enviroment than that encountered in hadron-hadron collisions
The main requirements imposed on the data sample were: an electron candidate with Ee′ > 10 GeV; a vertex position along the beam axis in the range |Z| < 34 cm; 38 < (E − PZ) < 65 GeV, where E is the total energy as measured by the CAL, E = i Ei, and PZ is the Z component of the vector P = i Eiri; in both cases the sum runs over all CAL cells, Ei is the energy of the CAL cell i andri is a unit vector along the line joining the reconstructed vertex and the geometric centre of the cell i; Q2 > 125 GeV2; and | cos γh| < 0.65
The uncertainty of the NLO QCD calculations is shown: the uncertainties from the anti-kT predictions are of a similar size as those encountered for the kT algorithm [4], and those for Seedless Infrared-Safe” cone (SIScone) are somewhat larger at low ETje,tB and low Q2
Summary
Jet production at high transverse energies in neutral-current (NC) deep inelastic ep scattering (DIS) at HERA provides unique tests of perturbative QCD (pQCD) in a cleaner hadron-like enviroment than that encountered in hadron-hadron collisions. The observables used to test pQCD included inclusive-jet [2,3,4,5,6,7,8,9], dijet [4, 6, 9,10,11] and multijet [9, 12,13,14] cross sections and the internal structure of jets [15,16,17,18] defined using the kT cluster algorithm [19] in the longitudinally invariant inclusive mode [20]. New determinations of αs(MZ) were obtained so as to quantify the performance of the anti-kT and SIScone algorithms in comparison with that of the kT analysis
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