Inclusive-jet cross sections in NC DIS at HERA and a comparison of the kT, anti-kT and SIScone jet algorithms

TL;DR

This work measures inclusive-jet cross sections in neutral-current DIS at HERA using anti-kT and SIScone algorithms in the Breit frame, comparing results with the k_T algorithm and NLO QCD predictions. It investigates the performance and theoretical description of three jet algorithms, including hadronization corrections and cross-section ratios up to O(α_s^3). The results show that all three algorithms yield similar cross sections and that NLO QCD describes the data with comparable precision, while ratios of cross sections across algorithms are accurately predicted. An extraction of α_s(M_Z) from the high-Q^2 data yields values consistent across anti-kT, SIScone, and k_T and in agreement with the world average, supporting the robustness of these algorithms in hadron-like environments.

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 Q^2 > 125 GeV^2 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(alphas^3) terms. Values of alphas(Mz) were extracted from the data; the results are compatible with and have similar precision to the value extracted from the kT analysis.

Figures (6)

• Figure 1: Examples of Feynman diagrams contributing to inclusive-jet production in the Breit frame up to ${\cal O}(\alpha_s^3)$. The calculations of inclusive-jet cross sections up to ${\cal O}(\alpha_s^2)$ include the (a) leading-order diagrams and (b) virtual and (d) real corrections. The lowest-order diagrams that contribute to the cross-section difference between the anti-$k_T$ and $k_T$ algorithms are of type (f). The calculations of the cross-section difference between the SIScone and $k_T$ algorithms include diagrams of type (d), (e) and (f).
• Figure 2: The measured differential cross-sections (a) $d\sigma/dE^{\rm jet}_{T,{\rm B}}$ and (b) $d\sigma/dQ^2$ for inclusive-jet production (dots) using different jet algorithms. The NLO QCD calculations with $\mu_R=E^{\rm jet}_{T,{\rm B}}$ (solid lines) are also shown. The cross sections for the anti-$k_T$ and $k_T$pl:b649:12 algorithms were multiplied by the scale factors indicated in brackets to aid visibility. The error bars on the data points are smaller than the marker size and are therefore not visible. The shaded bands display the uncertainty due to the absolute energy scale of the jets. The lower part of the figures shows the hadronisation-correction factor applied to the NLO calculations together with its uncertainty (hatched bands) for each jet algorithm; the hadronisation-correction factor for the $k_T$ algorithm was shifted by the value indicated in brackets to aid visibility.
• Figure 3: The ratios between the measured cross-sections (a) $d\sigma/dE^{\rm jet}_{T,{\rm B}}$ and (b) $d\sigma/dQ^2$ and the NLO QCD calculations (dots). The inner error bars represent the statistical uncertainty. The outer error bars show the statistical and systematic uncertainties, not associated with the uncertainty of the absolute energy scale of the jets, added in quadrature. The hatched bands display the total theoretical uncertainty and the shaded bands display the jet-energy scale uncertainty. The ratios of the measured cross sections (dots) anti-$k_T$/$k_T$, SIScone/$k_T$ and anti-$k_T$/SIScone as functions of (c) $E^{\rm jet}_{T,{\rm B}}$ and (d) $Q^2$. In these plots, the outer error bars include also the uncertainty of the absolute energy scale of the jets. The predicted ratios based on calculations which include up to ${\cal O}(\alpha_s^3)$ terms are also shown (solid lines). The hatched bands display the theoretical uncertainty on the ratio.
• Figure 4: Overview of the theoretical relative uncertainties for the inclusive-jet cross sections in the kinematic range of the measurements as functions of (a) $E^{\rm jet}_{T,{\rm B}}$ and (b) $Q^2$ for the anti-$k_T$ (shaded areas) and SIScone (hatched areas) jet algorithms. Shown are the relative uncertainties induced by the terms beyond NLO, those on the proton PDFs, that on the value of $\alpha_s(M_Z)$ and that on the modelling of the QCD cascade.
• Figure 5: The measured differential cross-section $d\sigma/dE^{\rm jet}_{T,{\rm B}}$ for inclusive-jet production in different regions of $Q^2$ (dots) using the (a) anti-$k_T$ and (b) SIScone jet algorithms. The measured and predicted cross sections have been multiplied by a scale factor as indicated in brackets to aid visibility. Other details as in the captions to Figs. \ref{['fig1']} and \ref{['fig2']}.