› › Measurements Of Jet Multiplicity And Differential Production Cross Sections Of Z Jets Events In Proton Proton Collisions At U221as

Measurements of Jet Multiplicity and Differential Production Cross Sections of Z + Jets Events in Proton-proton Collisions at {u221A}s

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File Size : 30,78 MB

Release : 2015

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Measurements of differential cross sections are presented for the production of a Z boson and at least one hadronic jet in proton-proton collisions at √s = 7 TeV, recorded by the CMS detector, using a data sample corresponding to an integrated luminosity of 4.9 inverse femtobarns. The jet multiplicity distribution is measured for up to six jets. The differential cross sections are measured as a function of jet transverse momentum and pseudorapidity for the four highest transverse momentum jets. The distribution of the scalar sum of jet transverse momenta is also measured as a function of the jet multiplicity. The measurements are compared with theoretical predictions at leading and next-to-leading order in perturbative QCD.



Measurements of Differential Cross Sections of Z/gamma*+jets+X Events in Proton Anti-proton Collisions at S**ư

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Page : 11 pages

File Size : 41,63 MB

Release : 2009

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We present cross section measurements for Z/?* + jets + X production, differential in the transverse momenta of the three leading jets. The data sample was collected with the D0 detector at the Fermilab Tevatron p{bar p} collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of 1 fb−1. Leading and next-to-leading order perturbative QCD predictions are compared with the measurements, and agreement is found within the theoretical and experimental uncertainties. We also make comparisons with the predictions of four event generators. Two parton-shower-based generators show significant shape and normalization differences with respect to the data. In contrast, two generators combining tree-level matrix elements with a parton shower give a reasonable description of the shapes observed in data, but the predicted normalizations show significant differences with respect to the data, reflecting large scale uncertainties. For specific choices of scales, the normalizations for either generator can be made to agree with the measurements.



Measurements of Differential Cross Sections of Z/gamma*+jets+X Events in Proton Anti-proton Collisions at S**1/2

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Page : 11 pages

File Size : 10,39 MB

Release : 2009

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We present cross section measurements for Z/[gamma]* + jets + X production, differential in the transverse momenta of the three leading jets. The data sample was collected with the D0 detector at the Fermilab Tevatron p{bar p} collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of 1 fb−1. Leading and next-to-leading order perturbative QCD predictions are compared with the measurements, and agreement is found within the theoretical and experimental uncertainties. We also make comparisons with the predictions of four event generators. Two parton-shower-based generators show significant shape and normalization differences with respect to the data. In contrast, two generators combining tree-level matrix elements with a parton shower give a reasonable description of the shapes observed in data, but the predicted normalizations show significant differences with respect to the data, reflecting large scale uncertainties. For specific choices of scales, the normalizations for either generator can be made to agree with the measurements.



Measurements of the Differential Production Cross Sections for a Z Boson in Association with Jets in Pp Collisions at $\sqrt{s}$

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File Size : 37,35 MB

Release : 2016

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Cross sections for the production of a Z boson in association with jets in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$=8 TeV are measured using a data sample collected by the CMS experiment at the LHC corresponding to 19.6 inverse femtobarns. Differential cross sections are presented as functions of up to three observables that describe the jet kinematics and the jet activity. Correlations between the azimuthal directions and the rapidities of the jets and the Z boson are studied in detail. The predictions of a number of multileg generators with leading or next-to-leading order accuracy are compared with the measurements. The comparison shows the importance of including multi-parton contributions in the matrix elements and the improvement in the predictions when next-to-leading order terms are included.





Measurements of Differential Cross Sections for Associated Production of a W Boson and Jets in Proton-proton Collisions at $\sqrt{s}$

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File Size : 36,79 MB

Release : 2016

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Differential cross sections for a W boson produced in association with jets are measured in a data sample of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the CMS detector and corresponding to an integrated luminosity of 19.6 inverse femtobarns. The W bosons are identified through their decay mode W to mu nu. The cross sections are reported as functions of jet multiplicity, transverse momenta, and the scalar sum of jet transverse momenta (HT) for different jet multiplicities. Distributions of the angular correlations between the jets and the muon are examined, as well as the average number of jets as a function of HT and as a function of angular variables. The measured differential cross sections are compared with tree-level and higher-order recent event generators, as well as next-to-leading-order and next-to-next-to-leading-order theoretical predictions. The agreement of the generators with the measurements builds confidence in their use for the simulation of W+jets background processes in searches for new physics at the LHC.



Measurement of Inclusive Jet Cross-sections in Z/gamma*( ---] E+ E- ) + Jets Production in P Anti-p Collisions at S**1/2

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Page : 7 pages

File Size : 20,95 MB

Release : 2007

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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 p{bar p} collisions at √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



Comparison of the Z$/\gamma^{*}$ + Jets to $\gamma$ + Jets Cross Sections in Pp Collisions at $\sqrt{s}$

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Page : 40 pages

File Size : 45,16 MB

Release : 2015

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In this study, a comparison of the differential cross sections for the processes Z/[gamma] * + jets and photon ([gamma])+jets is presented. The measurements are based on data collected with the CMS detector at √s = 8 TeV corresponding to an integrated luminosity of 19.7 fb-1. The differential cross sections and their ratios are presented as functions of pT. The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/[gamma]* pT to the sum of all jet transverse momenta and of the ratio of the Z/[gamma]* pT to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.



Measurement of the Production Cross Section of Jets in Association with a Z Boson in 8 TeV Proton-proton Collisions with the ATLAS Detector

Author : Rodger Mantifel

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File Size : 46,67 MB

Release : 2017

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"This thesis presents the measurement of the production cross sections of jets in association with a Z boson in proton-proton collisions at √s = 8 TeV with an integrated luminosity of 20.3 fb−1 recorded by the ATLAS experiment at the Large Hadron Collider at CERN. Inclusive and differential Z/[gamma]∗(→ e+e−)+jets cross sections are measured for jets with a transversemomentum pT(jet) > 30 GeV and rapidity |y(jet)| 4.4. Z boson candidates are identified by their decay into electron pairs. In order to stringently probe the modelling of Z/[gamma]∗+jets production by Monte Carlo generators in regions of high-pT phase space typical for Higgs boson decay and searches for new physics, events with high-pT final states are investigated. High-pT final states are defined as events with either pT(Z) 300 GeV or pT(leading jet) > 300 GeV. A set of four observables, sensitive to the topology of the event, are measured for the standard event selection as well as in the regions of high-pT phase space. The results from data are unfolded to particle level and compared to calculations of the matrix element from Monte Carlo generators Alpgen+Pythia and Sherpa interfaced to a parton shower. The results show that Sherpa tends to model Z/[gamma]∗+jets production in high-pT regions of phase space much better than Alpgen+Pythia." --



Differential Cross Section Measurements for the Production of a W Boson in Association with Jets in Proton-proton Collisions at $\sqrt S

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Page : 26 pages

File Size : 39,86 MB

Release : 2014

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Our measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. Furthermore, the data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb-1. The measured cross sections are compared to predictions from Monte Carlo generators, MADGRAPH + PYTHIAand SHERPA, and to next-to-leading-order calculations from BLACKHAT + SHERPA. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.