Production Of Jets In Association Research Articles

Measurement of the inclusive cross-section for the production of jets in association with a Z boson in proton–proton collisions at 8 TeV using the ATLAS detector

The inclusive cross-section for jet production in association with a Z boson decaying into an electron–positron pair is measured as a function of the transverse momentum and the absolute rapidity of jets using 19.9 fb^{-1} of sqrt{s}=8 TeV proton–proton collision data collected with the ATLAS detector at the Large Hadron Collider. The measured Ztext { + jets} cross-section is unfolded to the particle level. The cross-section is compared with state-of-the-art Standard Model calculations, including the next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations, corrected for non-perturbative and QED radiation effects. The results of the measurements cover final-state jets with transverse momenta up to 1 TeV, and show good agreement with fixed-order calculations.

Measurements of the Vector boson production with the ATLAS Detector

The electroweak sector of the Standard Model can be tested by precision measurements of its fundamental parameters, such as the W boson mass or the electroweak mixing angle. In this contribution we present the first measurement of the W boson mass, based on the 7 TeV data set corresponding to an integrated luminosity of 4.6 fb-1. With this data set the detector and physics modelling have been studied in great detail, leading to an overall uncertainty of 19 MeV. The ATLAS collaboration also performed a new precise triple differential Z/γ* Drell-Yan cross-section measurement as a function of the dilepton mass, the dilepton rapidity and cos θ* defined in the Collins-Soper frame. This measurement provides sensitivity to the PDFs and the Z forward-backward asymmetry, AFB, which is derived and will be presented. The latter builds the foundation for a possible future extraction of the weak-mixing angle. The production of jets in association with vector bosons is an important process to study perturbative QCD in a multi-scale environment. The ATLAS collaboration has performed new measurements of vector boson plus jets cross sections, differential in several kinematic variables, in proton-proton collision data, taken at center-of-mass energies of 8 TeV and 13 TeV. These measurements are presented and compared to state-of-the art theory predictions. They are sensitive to higher-order pQCD effects, and can be used to constrain the proton structure. In addition, we present a new measurement of the splitting scales of the kt jet-clustering algorithm for final states containing a Z-boson candidate at a centre-of-mass energy of 8 TeV.

Measurements of the vector boson production with the ATLAS detector

Measurements of the Drell-Yan production of W and Z bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new high precision measurements at a center-of-mass energy of 7 TeV. The measurements are performed for W+, W- and Z bosons integrated and as a function of the boson or lepton rapidity and the Z mass. Unprecedented precision is reached and strong constraints on Parton Distribution Functions, in particular the strange density are found. Z boson cross sections are also measured at center-of-mass energies of 8 TeV and 13 TeV, and cross-section ratios to the top-quark pair production have been derived. This ratio measurement leads to a cancellation of systematic effects and allows for a high precision comparison to the theory predictions. The production of jets in association with vector bosons is a further important process to study perturbative QCD in a multi-scale environment. The ATLAS collaboration has performed new measurements of Z boson plus jets cross sections, differential in several kinematic variables, in proton-proton collision data taken at a center-of-mass energy of 13 TeV. The measurements are compared to state-of-the art theory predictions. They are sensitive to higher-order pQCD effects, probe flavour and mass schemes and can be used to constrain the proton structure. In addition, a new measurement of the splitting scales of the kt jet-clustering algorithm for final states containing a Z boson candidate at a center-of-mass energy of 8 TeV is presented.

Precision Measurements with an Electroweak Boson in the Final State with the ATLAS Detector

Measurements of the Drell-Yan production of [Formula: see text] and [Formula: see text] bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new measurements for [Formula: see text], [Formula: see text] and [Formula: see text] boson production, reaching unprecedented precision and strong constraints on parton distribution functions, in particular the strange quark density. Studying jet production in association with a vector boson, perturbative QCD predictions can be tested in a multi-scale environment. Once the QCD aspects of the vector boson production are understood, high precision measurements aim at the tests of the electroweak sector, such as measuring the [Formula: see text] boson mass. Here, a selection of recent ATLAS measurements, as presented at the 21st Particles and Nuclei International Conference, in September 2017 in Beijing, China, is discussed.

Study of Jet Quenching with Z+jet Correlations in Pb-Pb and pp Collisions at sqrt[s]_{NN}=5.02 TeV.

The production of jets in association with Z bosons, reconstructed via the μ^{+}μ^{-} and e^{+}e^{-} decay channels, is studied in pp and, for the first time, in Pb-Pb collisions. Both data samples were collected by the CMS experiment at the LHC, at a nucleon-nucleon center-of-mass energy of 5.02TeV. The Pb-Pb collisions were analyzed in the 0%-30% centrality range. The back-to-back azimuthal alignment was studied in both pp and Pb-Pb collisions for Z bosons with transverse momentum p_{T}^{Z}>60 GeV/c and a recoiling jet with p_{T}^{jet}>30 GeV/c. The p_{T} imbalance x_{jZ}=p_{T}^{jet}/p_{T}^{Z}, as well as the average number of jet partners per Z, R_{jZ}, was studied in intervals of p_{T}^{Z}. The R_{jZ} is found to be smaller in Pb-Pb than in pp collisions, which suggests that in Pb-Pb collisions a larger fraction of partons associated with the Z bosons fall below the 30 GeV/c p_{T}^{jet} threshold because they lose energy.

Jet production in association with vector bosons or top quarks

The LHC experiments ATLAS and CMS have measured [Formula: see text] + jets and [Formula: see text] + jets final states over a large energy range in data collected between 2010 and 2012 at [Formula: see text] and [Formula: see text]. The results have been compared to pQCD calculations at NLO and have been used to validate novel Monte Carlo techniques.

Measurements of vector bosons plus jets production with the ATLAS detector at the LHC

The production of jets in association with a W or Z boson in proton-proton collisions at √s = 7 TeV is measured with the ATLAS detector at the LHC. The cross sections, differential in several kinematic variables, have been measured up to high jet multiplicities and are compared to new higher-order QCD calculations. Measurements of vector bosons in association with heavy flavor, such as W+c and W+b production, have unique sensitivity to the heavy quark density of the proton. Differential cross sections are presented and compared to QCD predictions at NLO.

W/Z+jet(s) production in pp collisions at $\boldsymbol{\sqrt{s}}=7\,\,\text{TeV}$

The measurements of the cross-sections are presented for the production of jets in association with W and Z bosons reconstructed in their decays to electrons and muons. The results are based on 36 pb − 1 of pp collisions at \(\sqrt{s} = 7\) TeV collected by the CMS Collaboration. Jets are reconstructed with the CMS particle flow algorithm and must pass a transverse momentum threshold of 30 GeV. The study presents the ratios \({\sigma}(V+\geq \text{$n$-jet})/{\sigma}({V})\) and \(\sigma(V+\geq \textit{n-{\rm jet}})/\sigma(V+\geq(n-1)\)-jet). The comparison between the data and the Monte Carlo prediction is also showed.

W/Z+jets with the CMS detector

We present a study of jet production in association with W and Z bosons in proton-proton collisions at TeV using the full 2010 data set collected by the CMS experiment corresponding to an integrated luminosity of 36±4 pb−1. The production of vector bosons with jets provides a stringent and important test of perturbative QCD, and is an important background to the study of top quark properties and in searches for new physics. We report the inclusive rates of jets produced (normalized to the total cross section) as well as the ratios σ(V + (n + 1)-jets)/σ(V + n-jets) for a jet threshold of 30 GeV. We also present a measurement of Z → ll + b and the first test of the Berends-Giele scaling at TeV.

Production of Jets in Association with W and Z at ATLAS

The study of final states with hadronic jets accompanying a W or Z boson is of high importance at hadronic colliders both to understand Standard Model processes and measure background contribution to Beyond the Standard Model searches. In view of the imminent start up of the LHC, we present the ATLAS prospects for the cross-section measurement of W / Z + jets events in proton-proton collisions at 14 TeV centre of mass energy. The statistical and systematic limitations are discussed in terms of probing perturbative QCD predictions and Monte Carlo generators.

Higher-order corrections to jet cross sections in hadron colliders

We describe a general method of calculating the fully differential cross section for the production of jets at next-to-leading order in a hadron collider. This method is based on a “crossing” of next-to-leading order calculations with all partons in the final state. The method introduces universal crossing functions that allow a modular approach to next-to-leading order calculations for any process with initial state partons. These techniques are applied to the production of jets in association with a vector boson including all decay correlations of the final state observables.

Measurement of the strong coupling constant alpha s in W-boson production at the CERN proton-antiproton collider.

The strong coupling constant {alpha}{sub {ital s}} has been determined from a study of the reaction {ital {bar p}p}{r arrow}{ital W}{sup {plus minus}}{ital X}, {ital W}{r arrow}{ital e}{nu} at {radical}{ital s} of 630 GeV in the UA1 experiment at CERN. The measurement is based upon a study of jet production in association with {ital W} bosons. The result obtained is {alpha}{sub {ital s}}({ital M}{sub {ital W}}{sup 2})=0.127{plus minus}0.026(stat){plus minus}0.034(syst).