Measurement Of Jet Cross Section Research Articles

Parton distribution functions and QCD coupling constant from LHC and non-LHC data

We present a new QCD analysis of parton distribution functions (PDFs) at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). In the present paper, the role of special types of experimental measurements for extracting PDFs is investigated, and simultaneously the values of the strong coupling constant are determined. Essential elements of this QCD analysis are the HERA combined data as a base, heavy-quark cross-section measurement together with Tevatron data on jet production and H1 and ZEUS jet cross sections as ``non-LHC'' data, and especially the ``LHC'' dataset for top-quark and jet cross sections. These different datasets have allowed detailed information at low $x$, providing worthwhile information on the nucleon's flavor, and have played an important role for some PDFs at large-$x$ and strong coupling constant. Since the large-$x$ gluon PDF benefits from an accurate determination of quark PDFs, we have enough motivation to focus on the top-quark production and jet cross-section measurements from LHC to find the impact of these data on the gluon PDF and strong coupling constant. These experimental data have an impact on the relative uncertainties of PDF. The gluon PDF at large $x$ and the values of ${\ensuremath{\alpha}}_{s}({M}_{Z}^{2})$ are affected significantly. Although the main motivation of this paper is to focus on the gluon PDF and its uncertainty at large-$x$, giving notice to heavy PDF behavior in this region is also very important. We study the intrinsic charm (IC) using the BHPS model together with our extracted extrinsic charm PDF at large $x$, which can be very worthwhile for future experiments at the LHC.

Addendum to: Measurement and QCD analysis of double-differential inclusive jet cross sections in proton-proton collisions at sqrt{textrm{s}} = 13 TeV

A measurement of the inclusive jet production in proton-proton collisions at the LHC at $\sqrt{s}$ = 13 TeV is presented. The double-differential cross sections are measured as a function of the jet transverse momentum $p_\mathrm{T}$ and the absolute jet rapidity $\lvert y \rvert$. The anti-$k_\mathrm{T}$ clustering algorithm is used with distance parameter of 0.4 (0.7) in a phase space region with jet $p_\mathrm{T}$ from 97 GeV up to 3.1 TeV and $\lvert y \rvert$ $\lt$ 2.0. Data collected with the CMS detector are used, corresponding to an integrated luminosity of 36.3 fb$^{-1}$ (33.5 fb$^{-1}$). The measurement is used in a comprehensive QCD analysis at next-to-next-to-leading order, which results in significant improvement in the accuracy of the parton distributions in the proton. Simultaneously, the value of the strong coupling constant at the Z boson mass is extracted as $\alpha_\mathrm{S}$(Z) = 0.1170 $\pm$ 0.0019. For the first time, these data are used in a standard model effective field theory analysis at next-to-leading order, where parton distributions and the QCD parameters are extracted simultaneously with imposed constraints on the Wilson coefficient $c_1$ of 4-quark contact interactions.

Measurement and QCD analysis of double-differential inclusive jet cross sections in proton-proton collisions at sqrt{s} = 13 TeV

A measurement of the inclusive jet production in proton-proton collisions at the LHC at sqrt{s} = 13 TeV is presented. The double-differential cross sections are measured as a function of the jet transverse momentum pT and the absolute jet rapidity |y|. The anti-kT clustering algorithm is used with distance parameter of 0.4 (0.7) in a phase space region with jet pT from 97 GeV up to 3.1 TeV and |y| < 2.0. Data collected with the CMS detector are used, corresponding to an integrated luminosity of 36.3 fb−1 (33.5 fb−1). The measurement is used in a comprehensive QCD analysis at next-to-next-to-leading order, which results in significant improvement in the accuracy of the parton distributions in the proton. Simultaneously, the value of the strong coupling constant at the Z boson mass is extracted as αS(mZ) = 0.1170±0.0019. For the first time, these data are used in a standard model effective field theory analysis at next-to-leading order, where parton distributions and the QCD parameters are extracted simultaneously with imposed constraints on the Wilson coefficient c1 of 4-quark contact interactions.

Erratum to: Determination of the strong coupling constant αs(mZ)in next-to-next-to-leading order QCD using H1 jet cross section measurements

Erratum to: Determination of the strong coupling constant αs(mZ)in next-to-next-to-leading order QCD using H1 jet cross section measurements

Determination of αs in NNLO QCD using H1 jet cross section measurements

Measurements of jet cross sections in neutral current deep-inelastic scattering (NC DIS) using data taken with the H1 detector at HERA are accomplished by the precision measurement of double-differential inclusive jet, dijet and trijet cross sections at low photon virtualities 5.5 &lt; Q2 &lt; 80 GeV2, and by extending previous inclusive jet measurements in the range 150 &lt; Q2 &lt; 15000 GeV2 to low transverse jet momenta 5 &lt; PT &lt; 7 GeV. The strong coupling constant at the Z-boson mass, αs(mZ), is determined in next-to-next-to-leading order (NNLO) QCD using H1 inclusive jet and dijet cross section measurements. Complementary, αs(mZ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with the QCD expectations.

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 of the cross section for isolated-photon plus jet production in pp collisions at [formula omitted] TeV using the ATLAS detector

The dynamics of isolated-photon production in association with a jet in proton–proton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb−1. Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti-kt algorithm with radius parameter R=0.4 and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements.

Measurements of event properties and multi-differential jet cross sections and impact of CMS measurements on Proton Structure and QCD parameters

We present results on the measurements of characteristics of events with jets including jet-charge, investigations of shapes and jet mass distributions. The measurements are compared to theoretical predictions including those matched to parton shower and hadronization. Multi-differential jet cross sections are also presented over a wide range in transverse momenta from inclusive jets to multi-jet final states. These measurements have an impact on the determination of the strong coupling constant as well as on parton distribution functions (PDFs) and are helpful in the treatment of heavy flavours in QCD analyses. We also show angular correlations in multi-jet events at highest center-of-mass energies and compare the measurements to theoretical predictions including higher order parton radiation and coherence effects. Measurements of cross sections of jet and top-quark pair production are in particular sensitive to the gluon distribution in the proton, while the electroweak boson production - inclusive or associated with charm or beauty quarks - gives insight into the flavour separation of the proton sea and to the treatment of heavy quarks in PDF-related studies.

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

A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities 5.5<Q^2 <80,mathrm {GeV}^2 and inelasticities 0.2<y<0.6 is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of 290,mathrm {pb}^{-1}. Double-differential inclusive jet, dijet and trijet cross sections are measured simultaneously and are presented as a function of jet transverse momentum observables and as a function of Q^2. Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective Q^2-interval are also determined. Previous results of inclusive jet cross sections in the range 150<Q^2 <15{,}000,mathrm {GeV}^2 are extended to low transverse jet momenta 5<P_mathrm{T}^mathrm{jet} <7,mathrm {GeV} . The data are compared to predictions from perturbative QCD in next-to-leading order in the strong coupling, in approximate next-to-next-to-leading order and in full next-to-next-to-leading order. Using also the recently published H1 jet data at high values of Q^2, the strong coupling constant alpha _s(M_Z) is determined in 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.

Measurement of the double-differential inclusive jet cross section in proton-proton collisions at [Formula: see text

A measurement of the double-differential inclusive jet cross section as a function of jet transverse momentum p_{mathrm {T}} and absolute jet rapidity |y | is presented. The analysis is based on proton–proton collisions collected by the CMS experiment at the LHC at a centre-of-mass energy of 13,text {TeV}. The data samples correspond to integrated luminosities of 71 and 44,text {pb}^text {-1} for |y |<3 and 3.2<|y |<4.7, respectively. Jets are reconstructed with the anti-k_{mathrm {t}} clustering algorithm for two jet sizes, R, of 0.7 and 0.4, in a phase space region covering jet p_{mathrm {T}} up to 2,text {TeV} and jet rapidity up to |y | = 4.7. Predictions of perturbative quantum chromodynamics at next-to-leading order precision, complemented with electroweak and nonperturbative corrections, are used to compute the absolute scale and the shape of the inclusive jet cross section. The cross section difference in R, when going to a smaller jet size of 0.4, is best described by Monte Carlo event generators with next-to-leading order predictions matched to parton showering, hadronisation, and multiparton interactions. In the phase space accessible with the new data, this measurement provides a first indication that jet physics is as well understood at sqrt{s}=13,text {TeV} as at smaller centre-of-mass energies.

Measurement of the inclusive jet cross section in pp collisions at $$\sqrt{s} = 2.76\,\text {TeV}$$ s = 2.76 TeV

The double-differential inclusive jet cross section is measured as a function of jet transverse momentum pT and absolute rapidity y, using proton-proton collision data collected with the CMS experiment at the LHC, at a center-of-mass energy of sqrt(s) = 2.76 TeV and corresponding to an integrated luminosity of 5.43 inverse picoboarns. Jets are reconstructed within the pT range of 74 to 592 GeV and the rapidity range |y| < 3.0. The reconstructed jet spectrum is corrected for detector resolution. The measurements are compared to the theoretical prediction at next-to-leading-order QCD using different sets of parton distribution functions. This inclusive cross section measurement explores a new kinematic region and is consistent with QCD predictions.

Towards the understanding of jet shapes and cross sections in heavy ion collisions using soft-collinear effective theory

We calculate the jet shape and the jet cross section in heavy ion collisions using soft-collinear effective theory (SCET) and its extension with Glauber gluon interactions in the medium (SCET$_{\rm G}$). We use the previously developed framework to systematically resum the jet shape at next-to-leading logarithmic accuracy, and we consistently include the medium modification by incorporating the leading order medium-induced splitting functions. The calculation provides, for the first time, a quantitative understanding of the jet shape modification measurement in lead-lead collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV at the LHC. The inclusive jet suppression is also calculated within the same framework beyond the traditional concept of parton energy loss, and the dependence on the centrality, the jet radius and the jet kinematics is examined. In the end we present predictions for the anticipated jet shape and cross section measurements in lead-lead collisions at $\sqrt{s_{\rm NN}}\approx5.1$ TeV at the LHC.

Differential Z + jet cross section measurements at 8 TeV

The measurement of differential cross section of a Z boson produced in association with jets is presented. The cross section is presented with respect to various jet kinematic variables where the Z bosons are reconstructed from opposite sign lepton pairs. The analysis is based on data of proton proton collisions with the centre of mass energy of 8 TeV collected in 2012 by the CMS experiment at LHC corresponding to 19.8 fb−1 of integrated luminosity. Obtained results are compared with different generators and are shown to be consistent with the Standard Model predictions.

Low pT Jet Cross Section Measurement in pp Collisions at [formula omitted

Recent measurement of inclusive jet cross sections at low jet transverse momenta 21<pT<74 GeV/c in the rapidity region of |y|<4.7 is presented. Jets are reconstructed with the anti-kT clustering algorithm for a jet size parameter R=0.7. The data is collected with the CMS detector using pp collisions at s=8 TeV, exploiting special low-pileup runs of the LHC. The measured jet cross section is corrected for detector effects. The results are compared to theoretical predictions of next-to-leading order (NLO) QCD calculations.

Jet production and αs measurement at CMS

The measurements of inclusive jet, dijet and trijet cross sections, of the dijet azimuthal decorrelations, the ratio of the inclusive 3-jet to 2-jet cross sections are presented. The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at a center-of-mass energy of 7 and 8 TeV.

Measurements of inclusive jet and dijet cross sections at the Large Hadron Collider

This review discusses the measurements of the inclusive jet and dijet cross section performed by the experimental collaborations at the LHC during what is now being called LHC Run 1 (2009–2013). It summarises some of the experimental challenges and the techniques used in the measurements of jets cross sections during the LHC Run 1.

Measurement of the inclusive jet cross section in pp collisions at $\sqrt{s} = 2.76\,ext {TeV}

Measurement of the inclusive jet cross section in pp collisions at $\sqrt{s} = 2.76\,ext {TeV}

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.

Measurement of the inclusive jet cross-section in pp collisions at [Formula: see text] and comparison to the inclusive jet cross-section at [Formula: see text] using the ATLAS detector.

The inclusive jet cross-section has been measured in proton–proton collisions at sqrt{s} = 2.76~mbox{TeV} in a dataset corresponding to an integrated luminosity of 0.20~mbox {pb^{-1}} collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-k t algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum p T and jet rapidity y, covering a range of 20≤p T<430 GeV and |y|<4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at sqrt{s} = 7~mbox{TeV}, published by the ATLAS Collaboration, is calculated as a function of both transverse momentum and the dimensionless quantity x_{mathrm{T}} = 2 p_{mathrm{T}} / sqrt{s}, in bins of jet rapidity. The systematic uncertainties on the ratios are significantly reduced due to the cancellation of correlated uncertainties in the two measurements. Results are compared to the prediction from next-to-leading order perturbative QCD calculations corrected for non-perturbative effects, and next-to-leading order Monte Carlo simulation. Furthermore, the ATLAS jet cross-section measurements at sqrt{s} = 2.76~mbox{TeV} and sqrt{s}=7~mbox{TeV} are analysed within a framework of next-to-leading order perturbative QCD calculations to determine parton distribution functions of the proton, taking into account the correlations between the measurements.