Inclusive Jet Cross Section Research Articles

Inclusive-jet cross sections in NC DIS at HERA and a comparison of the [formula omitted], anti-[formula omitted] and SIScone jet algorithms

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.

Jet Tomography of High-Energy Nucleus-Nucleus Collisions at Next-to-Leading Order

We demonstrate that jet observables are highly sensitive to the characteristics of the vacuum and the in-medium QCD parton showers and propose techniques that exploit this sensitivity to constrain the mechanism of quark and gluon energy loss in strongly interacting plasmas. As a first example, we calculate the inclusive jet cross section in high-energy nucleus-nucleus collisions to O(alpha(s)(3)). Theoretical predictions for the medium-induced jet broadening and the suppression of the jet production rate due to cold and hot nuclear matter effects in Au+Au and Cu+Cu reactions at RHIC are presented.

Jet production in ep collisions at low Q 2 and determination of α s

The production of jets is studied in deep-inelastic e+p scattering at low negative four momentum transfer squared 5<Q^2<100 GeV^2 and at inelasticity 0.2<y<0.7 using data recorded by the H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb^-1. Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q^2 and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction xi. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling alpha_s.

Determination of the strong coupling constant from the inclusive jet cross section inpp¯collisions ats=1.96 TeV

We determine the strong coupling constant alphas and its energy dependence from the pT dependence of the inclusive jet cross section in ppbar collisions at sqrt(s)=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < pT < 145 GeV. Using perturbative QCD calculations to order O(alphas^3) combined with O(alphas^4) contributions from threshold corrections, we obtain alphas(MZ) = 0.1161 +0.0041 -0.0048. This is the most precise result obtained at a hadron-hadron collider.

Jet production in ep collisions at high Q 2 and determination of α s

The production of jets is studied in deep-inelastic e ± p scattering at large negative four momentum transfer squared 150<Q 2<15000 GeV2 using HERA data taken in 1999–2007, corresponding to an integrated luminosity of 395 pb−1. Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q 2, jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurements is $\alpha_{s}(M_{Z})=0.1168\pm0.0007\,\mathrm{(exp.)}{}^{+0.0046}_{-0.0030}\,\mathrm{(th.)}\pm 0.0016$ (PDF).

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.

Jets and [formula omitted] measurements in DIS at HERA

Recent measurements of jet production at HERA provide an excellent testing ground for perturbative QCD (pQCD) and allow improved determinations of the strong coupling, αs. A review of recent measurements of dijet and inclusive-jet cross sections in neutral current DIS (NC DIS) at HERA is presented, and the latest determinations of αs are shown.

CMS search plans and sensitivity to new physics with dijets

The compact muon solenoid (CMS) experiment will use dijets to search for physics beyond the standard model during early LHC running. The inclusive jet cross section as a function of jet transverse momentum, with 10 pb−1 of integrated luminosity, is sensitive to contact interactions beyond the reach of the Tevatron. The dijet mass distribution will be used to search for dijet resonances coming from new particles, for example an excited quark. Additional sensitivity to the existence of contact interactions or dijet resonances can be obtained by comparing dijet rates in two distinct pseudorapidity regions.

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.

Multijet cross sections in charged currente±pscattering at HERA

Jet cross sections were measured in charged-current deep inelastic e(+/-)p scattering at high boson virtualities Q(2) with the ZEUS detector at HERA II using an integrated luminosity of 0.36 fb(-1). Differential cross sections are presented for inclusive-jet production as functions of Q(2), Bjorken x and the jet transverse energy and pseudorapidity. The dijet invariant mass cross section is also presented. Observation of three- and four-jet events in charged-current e(+/-)p processes is reported for the first time. The predictions of next-to-leading-order (NLO) QCD calculations are compared to the measurements. The measured inclusive-jet cross sections are well described in shape and normalization by the NLO predictions. The data have the potential to constrain the u and d valence-quark distributions in the proton if included as input to global fits.

Measurement of the Inclusive Jet Cross Section inpp¯Collisions ats=1.96 TeV

We report on a measurement of the inclusive jet cross section in pp[over ] collisions at a center-of-mass energy sqrt[s]=1.96 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0.70 fb;{-1}. The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.

Inclusive jet and dijet production at HERA

The inclusive jet cross section in deep-inelastic scattering (DIS) and dijet cross-section in photo-production and DIS have been measured at s√ = 320 GeV at the electron-proton collider HERA by the H1 and ZEUS collaborations using data taken in 1998-2000 (HERA I) and in 2004-2007 (HERA II). Cross-sections are presented as a function of relevant kinematical variables such as boson virtuality Q2, proton (photon) momentum fraction carried by the interacting parton xp (xγ) or transverse energy ET of the jets. The data are compared to perturbative QCD (pQCD) predictions at next-to-leading order (NLO) and are in general in good agreement within the estimated theory error which exceeds the typical experimental uncertainty in most regions of phase-space. The sensitivity of these high-precision jet observables to QCD parameters such as the strong coupling αS and parameterisations of the parton density functions (PDF) of the proton and the photon are discussed.

Inclusive jet production at the tevatron using the CDF experiment

This contribution reports on measurements of the inclusive jet production cross section in pp collisions at s√s = 1.96 TeV. Two analyzes are presented: one uses the longitudinally invariant kT algorithm to reconstruct the jets, the other uses the midpoint algorithm. The data samples have been collected at CDF during the Run II of the Tevatron and correspond to integrated luminosities of 1.0 fb-1 for the kT study and 1.13 fb-1 for the midpoint one. The inclusive jet cross sections are measured as a function of the jet transverse momentum in five jet rapidity regions for jets in the ranges 54 < pTjet < 700 GeV/c and yjet| < 2.1. Nextto-leading order perturbative QCD predictions are in good agreement with the measured cross sections after including the non-perturbative corrections necessary to account for underlying event and hadronization effects.

Measurement of Inclusive Jet Cross Sections inZ/γ*(→e+e−)+jetsProduction inpp¯Collisions ats=1.96 TeV

Inclusive jet cross sections in Z/gamma^* events, with Z/gamma^* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in ppbar collisions at sqrt{s} = 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 1.7 fb^-1. The measurements cover the rapidity region | yjet | < 2.1 and the transverse momentum range ptjet > 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.

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.

Inclusive jet production using the k T algorithm at CDF

This contribution presents preliminary results on the inclusive jet production in p p ¯ collisions at s = 1.96 TeV . The measurements are carried out using the longitudinally invariant k T algorithm. The inclusive jet cross sections are measured as a function of the jet transverse momentum in five jet rapidity regions for jets in the ranges 54 p T j e t 700 GeV/c and | y j e t | 2.1 . The results are based on 1.0 fb −1 of data collected at CDF during the Run II of the Tevatron. They are in good agreement with next-to-leading order perturbative QCD predictions after including the non-perturbative corrections necessary to account for underlying event and hadronization effects.

Measurement of inclusive jet production in deep-inelastic scattering at high [formula omitted] and determination of the strong coupling

Inclusive jet production is studied in neutral current deep-inelastic positron–proton scattering at large four momentum transfer squared Q 2 > 150 GeV 2 with the H1 detector at HERA. Single and double differential inclusive jet cross sections are measured as a function of Q 2 and of the transverse energy E T of the jets in the Breit frame. The measurements are found to be well described by calculations at next-to-leading order in perturbative QCD. The running of the strong coupling is demonstrated and the value of α s ( M Z ) is determined. The ratio of the inclusive jet cross section to the inclusive neutral current cross section is also measured and used to extract a precise value for α s ( M Z ) = 0.1193 ± 0.0014 ( exp. ) −0.0030 +0.0047 ( th. ) ± 0.0016 ( pdf ) .

NLO QCD corrections to inclusive jet and hadron production in DIS

We analyze the order a 2 corrections to the single inclusive jet and hadron cross sections in lepton-nucleon deep inelastic scattering. The full calculations are done analytically, obtaining finite NLO partonic level cross sections for these processes. We show that in both cases the dominant partonic mechanism starts at order a 2 , being effectively a lowest order estimate, with the consequent large factorization scale uncertainty, and the likelihood of non-negligible corrections at the subsequent order in perturbation theory.

Jet-radius dependence of inclusive-jet cross sections in deep inelastic scattering at HERA

Differential inclusive-jet cross sections have been measured for different jet radii in neutral current deep inelastic ep scattering for boson virtualities Q^2 > 125 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb^-1. Jets were identified in the Breit frame using the k_T cluster algorithm in the longitudinally inclusive mode for different values of the jet radius R. Differential cross sections are presented as functions of Q^2 and the jet transverse energy, E_T,B^jet. The dependence on R of the inclusive-jet cross section has been measured for Q^2 > 125 and 500 GeV^2 and found to be linear with R in the range studied. Next-to-leading-order QCD calculations give a good description of the measurements for 0.5 <= R <= 1. A value of alpha_s(M_Z) has been extracted from the measurements of the inclusive-jet cross-section dsigma/dQ^2 with R=1 for Q^2 > 500 GeV^2: alpha_s(M_Z) = 0.1207 +- 0.0014 (stat.) -0.0033 +0.0035 (exp.) -0.0023 +0.0022 (th.). The variation of alpha_s with E_T,B^jet is in good agreement with the running of alpha_s as predicted by QCD.

Inclusive and heavy quark jet cross-sections from CDF

We present results for some QCD measurement recently performed by the CDF collaboration at the Tevatron collider: the inclusive jet cross section, the inclusive b-jet cross section and the b b ¯ cross section