Inclusive jet cross sections in the Breit frame in neutral current deep inelastic scattering at HERA and determination of alpha_s

TL;DR

This paper presents measurements of inclusive jet cross sections in neutral-current deep inelastic scattering at HERA (ZEUS) using the Breit frame and the $k_T$ algorithm, covering $Q^2>125$ GeV$^2$ and jet $E_T^{B}$ thresholds. The data are compared to NLO QCD predictions with MRST99 PDFs, including hadronization and $Z$-exchange corrections, showing good agreement at high $Q^2$ and high $E_T^{B}$ while revealing modest tensions at lower scales. A QCD fit to the measured cross sections yields a precise determination of the strong coupling constant, with best precision from $Q^2>500$ GeV$^2$: $
extrm{alpha}_s(M_Z)=0.1212^{+0.0017}_{-0.0017} ext{ (stat)}^{+0.0023}_{-0.0031} ext{ (syst)}^{+0.0028}_{-0.0027} ext{ (th)}$, in agreement with the world average and other high-precision measurements. The results validate perturbative QCD predictions for jet production in DIS and provide important cross-checks of the running of $
extrm{alpha}_s$ across a broad range of scales.

Abstract

Inclusive jet differential cross sections have been measured in neutral current deep inelastic e+p scattering for boson virtualities Q**2>125 GeV**2. The data were taken using the ZEUS detector at HERA and correspond to an integrated luminosity of 38.6 pb-1. Jets were identified in the Breit frame using the longitudinally invariant K_T cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy (E_T,jet), jet pseudorapidity and Q**2, for jets with E_T,jet>8 GeV. Next-to-leading-order QCD calculations agree well with the measurements both at high Q**2 and high E_T,jet. The value of alpha_s(M_Z), determined from an analysis of dsigma/dQ**2 for Q**2>500 GeV**2, is alpha_s(M_Z) = 0.1212 +/- 0.0017 (stat.) +0.0023 / -0.0031 (syst.) +0.0028 / -0.0027 (th.).

Figures (6)

• Figure 1: a) The differential cross-section $d\sigma/dQ^2$ for inclusive jet production with $E^B_{T,\rm{jet}} > 8$ GeV and $-2 < \eta^B_{\rm{jet}} < 1.8$ (filled dots). The inner error bars represent the statistical uncertainty. The outer error bars show the statistical and systematic uncertainties, not associated with the uncertainty in the absolute energy scale of the jets, added in quadrature. The shaded band displays the uncertainty due to the absolute energy scale of the jets. The NLO QCD calculations, corrected for hadronisation effects and using the MRST99 parameterisations of the proton PDFs, are shown for two choices of the renormalisation scale. b) The ratio between the measured $d\sigma/dQ^2$ and the NLO QCD calculation; the hatched band displays the total theoretical uncertainty. The shaded band in c) shows the magnitude and the uncertainty of the parton-to-hadron correction used to correct the NLO QCD predictions.
• Figure 2: a) The differential cross-section $d\sigma/dE^B_{T,\rm{jet}}$ for inclusive jet production with $E^B_{T,\rm{jet}} > 8$ GeV and $-2 < \eta^B_{\rm{jet}} < 1.8$ (filled dots). Other details are as described in the caption to Fig. \ref{['fig2']}.
• Figure 3: a) The differential cross-section $d\sigma/d\eta^B_{\rm{jet}}$ for inclusive jet production with $E^B_{T,\rm{jet}} > 8$ GeV and $-2 < \eta^B_{\rm{jet}} < 1.8$ (filled dots). Other details are as described in the caption to Fig. \ref{['fig2']}.
• Figure 4: The differential cross-section $d\sigma/dE^B_{T,\rm{jet}}$ for inclusive jet production with $E^B_{T,\rm{jet}} > 8$ GeV and $-2 < \eta^B_{\rm{jet}} < 1.8$ in different regions of $Q^2$ (filled dots). Each cross section has been multiplied by the scale factor indicated in brackets to aid visibility. Other details are as described in the caption to Fig. \ref{['fig2']}.
• Figure 5: Ratios between the differential cross-sections $d\sigma/dE^B_{T,\rm{jet}}$ presented in Fig. \ref{['fig6']} and NLO QCD calculations using the MRST99 parameterisations of the proton PDFs and $\mu_R=E^B_{T,\rm{jet}}$ (filled dots). Other details are as described in the caption to Fig. \ref{['fig2']}.