Measurement Of Inclusive Jet Cross Section Research Articles

Measurement of jet production in deep inelastic scattering and NNLO determination of the strong coupling at ZEUS

A new measurement of inclusive-jet cross sections in the Breit frame in neutral current deep inelastic scattering using the ZEUS detector at the HERA collider is presented. The data were taken in the years 2004–2007 at a centre-of-mass energy of 318GeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$318\\,\\,\ extrm{GeV}$$\\end{document} and correspond to an integrated luminosity of 347pb-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$347\\,\\,\ extrm{pb}^{-1}$$\\end{document}. The jets were reconstructed using the kt\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k_t$$\\end{document}-algorithm in the Breit reference frame. They have been measured as a function of the squared momentum transfer, Q2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q^2$$\\end{document}, and the transverse momentum of the jets in the Breit frame, p⊥,Breit\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_{\\perp ,\ ext {Breit}}$$\\end{document}. The measured jet cross sections are compared to previous measurements and to perturbative QCD predictions. The measurement has been used in a next-to-next-to-leading-order QCD analysis to perform a simultaneous determination of parton distribution functions of the proton and the strong coupling, resulting in a value of αs(MZ2)=0.1142±0.0017(experimental/fit)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha _s(M_Z^2) = 0.1142 \\pm 0.0017 \ ext {~(experimental/fit)}$$\\end{document}-0.0007+0.0006(model/parameterisation)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${}_{-0.0007}^{+0.0006} \ ext {~(model/parameterisation)}$$\\end{document}-0.0004+0.0006(scale)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${}_{-0.0004}^{+0.0006} \ ext {~(scale)}$$\\end{document}, whose accuracy is improved compared to similar measurements. In addition, the running of the strong coupling is demonstrated using data obtained at different scales.

Determination of the strong coupling constant using inclusive jet cross section data from multiple experiments

Inclusive jet cross section measurements from the ATLAS, CDF, CMS, D0, H1, STAR, and ZEUS experiments are explored for determinations of the strong coupling constant alpha _{text {s}} (M_{text {Z}}). Various jet cross section data sets are reviewed, their consistency is examined, and the benefit of their simultaneous inclusion in the alpha _{text {s}} (M_{text {Z}}) determination is demonstrated. Different methods for the statistical analysis of these data are compared and one method is proposed for a coherent treatment of all data sets. While the presented studies are based on next-to-leading order in perturbative quantum chromodynamics (pQCD), they lay the groundwork for determinations of alpha _{text {s}} (M_{text {Z}}) at next-to-next-to-leading order.

Measurement and QCD analysis of double-differential inclusive jet cross sections in pp collisions at sqrt{s}=8 TeV and cross section ratios to 2.76 and 7 TeV

A measurement of the double-differential inclusive jet cross section as a function of the jet transverse momentum pT and the absolute jet rapidity |y| is presented. Data from LHC proton-proton collisions at sqrt{s}=8 TeV, corresponding to an integrated luminosity of 19.7 fb−1, have been collected with the CMS detector. Jets are reconstructed using the anti-kT clustering algorithm with a size parameter of 0.7 in a phase space region covering jet pT from 74 GeV up to 2.5 TeV and jet absolute rapidity up to |y| = 3.0. The low-pT jet range between 21 and 74 GeV is also studied up to |y| = 4.7, using a dedicated data sample corresponding to an integrated luminosity of 5.6 pb−1. The measured jet cross section is corrected for detector effects and compared with the predictions from perturbative QCD at next-to-leading order (NLO) using various sets of parton distribution functions (PDF). Cross section ratios to the corresponding measurements performed at 2.76 and 7 TeV are presented. From the measured double-differential jet cross section, the value of the strong coupling constant evaluated at the Z mass is αS(MZ) = 0.1164− 0.0043+ 0.0060, where the errors include the PDF, scale, nonperturbative effects and experimental uncertainties, using the CT10 NLO PDFs. Improved constraints on PDFs based on the inclusive jet cross section measurement are presented.

Impact of CMS measurements on PDFs

Recently 2 analyses have been published by the CMS collaboration that study the effect of a specific CMS measurement on PDFs. A review of these studies is given here.The first analysis consists of a double differential inclusive jet cross-section measurement, performed on 4.7 fb−1 of data at √s = 7 TeV. Using the HERAFITTER code, the effect of adding this measurement in the PDF fit procedure together with DIS data from HERA-I is studied. The CMS data is able to significantly reduce the uncertainties on the gluon PDF, especially for gluons with large momenta relative to the proton (x > 0:01). A moderate reduction in the uncertainty of the u and d valence quark PDFs is also observed for x > 0:01. The quark PDFs are more directly probed by gauge boson production. Therefore the second analysis studies the effect of W-boson production measurements on PFDs. This consists of a W-boson charge asymmetry measurement and a study of W-boson production in association with a c-(anti-)quark, both performed on 5.0 fb−1 of data at √s = 7 TeV. A clear reduction in the uncertainty on the u and d valence quark PDFs is seen for x < 0:1. Furthermore the W-boson + c-quark production measurements allow for the determination of an independent s quark PDF, which is not possible on DIS data alone.

Searches for New Physics in Multijet Final States

A variety of new physics models predict heavy resonances that decay to multiple hadronic jets. These models include axigluons, colorons, diquarks, excited quarks, Randall-Sundrum gravitons, string resonances, and Z' models, among others. Other models make the prediction that high-pT jets will be suppressed, resulting in jet extinction. Using the data collected in 2012 at a center-of-mass energy of 8 TeV, the CMS Collaboration has made a baseline inclusive jet cross section measurement for comparison with new-physics searches, and then performed searches for jet extinction and resonances that decay to two hadronic jets. The results of these searches will be presented. No evidence of new physics has been observed, and these results set new limits on the parameters of these models.

Inclusive jet cross section measurement in ATLAS

The inclusive jet cross section has been measured in proton-proton collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The full 2010 data set has been used, consisting of a total integrated luminosity of 37 pb−1 . The anti-kt algorithm is used to identify jets with two jet radius parameters, R = 0.4 and R = 0.6. Jet shapes have been measured in order to validate the models for parton shower, fragmentation into hadrons, and the underlying event contributions contained in the event generators. The inclusive jet cross section measurement is presented as a function of jet transverse momentum and rapidity, for jets with transverse momentum from 20 GeV to 1.5 TeV in a rapidity range |y| up to 4.4. The data are compared to expectations based on next-to-leading order QCD corrected for non-perturbative effects, and to predictions obtained using POWHEG. In addition to a validation of the theory in a new kinematic regime, the data also provide sensitivity to parton distribution functions in a region where they are currently poorly constrained.

JET RESULTS, JET RECONSTRUCTION, AND UNDERLYING EVENT STUDIES AT CDF

We present recent results of jet studies from the CDF Collaboration. The inclusive jet cross section measurements using different clustering algorithms, dijet production, and vector boson plus jet production measurements, are discussed. We also present the first study of highly boosted and massive jets. The properties of these jets, including the mass of the jet and several other observables, such as angularity and planar flow, are discussed.

Erratum: Measurement of the inclusive jet cross section at the Fermilab Tevatronpp¯collider using a cone-based jet algorithm [Phys. Rev. D78, 052006 (2008)

We present a measurement of the inclusive jet cross section in p-pbar collisions at sqrt{s}=1.96 TeV based on data collected by the CDF II detector with an integrated luminosity of 1.13 fb^-1. The measurement was made using the cone-based Midpoint jet clustering algorithm in the rapidity region of |y|<2.1. The results are consistent with next-to-leading-order perturbative QCD predictions based on recent parton distribution functions (PDFs), and are expected to provide increased precision in PDFs at high parton momentum fraction x. The results are also compared to the recent inclusive jet cross section measurement using the k_T jet clustering algorithm, and we find that the ratio of the cross sections measured with the two algorithms is in agreement with theoretical expectations over a large range of jet transverse momentum and rapidity.

Measurement of the inclusive jet cross section at the Fermilab Tevatronpp¯collider using a cone-based jet algorithm

We present a measurement of the inclusive jet cross section in p-pbar collisions at sqrt{s}=1.96 TeV based on data collected by the CDF II detector with an integrated luminosity of 1.13 fb^-1. The measurement was made using the cone-based Midpoint jet clustering algorithm in the rapidity region of |y|<2.1. The results are consistent with next-to-leading-order perturbative QCD predictions based on recent parton distribution functions (PDFs), and are expected to provide increased precision in PDFs at high parton momentum fraction x. The results are also compared to the recent inclusive jet cross section measurement using the k_T jet clustering algorithm, and we find that the ratio of the cross sections measured with the two algorithms is in agreement with theoretical expectations over a large range of jet transverse momentum and rapidity.

Precision measurements of αs at hera

Recent determinations of αs (MZ) from the H1 and ZEUS Collaborations using inclusive-jet cross-section measurements in neutral current deep inelastic scattering at high Q2 are presented. A combined value of αs (MZ) = 0.1198±0.0019 (exp.)±0.0026 (th.) was obtained from these measurements. The determinations of αs at various scales clearly show the running of the coupling from HERA jet data alone and in agreement with the prediction of QCD.

Determination of the Jet Energy Scale

The uncertainty in jet energy scale is one of the dominating systematic errors for many measurements at hadron colliders – most notably for the measurement of the top-quark-mass, inclusive jet cross section measurements and last but not least for events with large missing transverse energy as expected in searches beyond the standard model. This talk will review the approaches taken at Tevatron towards controlling the jet energy scale and discuss prospects for the LHC experiments.

Measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA

A measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA is presented based on data with an integrated luminosity of 21.1 pb −1. The measurement is performed for photon virtualities Q 2 between 5 and 100 GeV 2, differentially in Q 2, in the jet transverse energy E T , in E T 2/ Q 2 and in the pseudorapidity η lab. With the renormalization scale μ R = E T , perturbative QCD calculations in next-to-leading order (NLO) give a good description of the data in most of the phase space. Significant discrepancies are observed only for jets in the proton beam direction with E T below 20 GeV and Q 2 below 20 GeV 2. This corresponds to the region in which NLO corrections are largest and further improvement of the calculations is thus of particular interest.