First Measurement of Hadronic Event Shapes in pp Collisions at sqrt(s)=7 TeV

Hadronic event shapes have been measured in proton-proton collisions at =7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

Approved Plots from QCD-10-013 ( click on plot to get .pdf )

Figure Abbreviated Caption
result_upper_central_transverse_thrust_pt1_90_125.pngresult_ratio_central_transverse_thrust_pt1_90_125.png result_upper_central_thrust_minor_pt1_90_125.pngresult_ratio_central_thrust_minor_pt1_90_125.png Distributions of the logarithm of the central transverse thrust (top left) and central thrust minor (top right) for events with a leading jet pT between 90 and 125 GeV/c, from data and from five MC simulations. The data distribution is unfolded to allow the comparison with the MC generator level distributions. The error bars on the data points represent the statistical uncertainty on the data after the unfolding, The shaded (blue) bands represent the sum of statistical and systematic errors. The lower plots show the ratio between data and the different MC samples.
result_upper_central_transverse_thrust_pt1_125_200.pngresult_ratio_central_transverse_thrust_pt1_125_200.png result_upper_central_thrust_minor_pt1_125_200.pngresult_ratio_central_thrust_minor_pt1_125_200.png Distributions of the logarithm of the central transverse thrust (top left) and central thrust minor (top right) for events with a leading jet pT between 125 and 200 GeV/c, from data and from five MC simulations. The data distribution is unfolded to allow the comparison with the MC generator level distributions. The error bars on the data points represent the statistical uncertainty on the data after the unfolding, The shaded (blue) bands represent the sum of statistical and systematic errors. The lower plots show the ratio between data and the different MC samples.
result_upper_central_transverse_thrust_pt1_200.pngresult_ratio_central_transverse_thrust_pt1_200.png result_upper_central_thrust_minor_pt1_200.pngresult_ratio_central_thrust_minor_pt1_200.png Distributions of the logarithm of the central transverse thrust (top left) and central thrust minor (top right) for events with a leading jet pT> 200 GeV/c, from data and from five MC simulations. The data distribution is unfolded to allow the comparison with the MC generator level distributions. The error bars on the data points represent the statistical uncertainty on the data after the unfolding, The shaded (blue) bands represent the sum of statistical and systematic errors. The lower plots show the ratio between data and the different MC samples.

Link to QCD-10-013 Paper in arXiv

Hadronic Event Shapes in pp Collisions at 7 TeV

Abstract

Hadronic event shapes are studied with a data sample of 7 TeV proton-proton collisions collected with the CMS detector at the Large Hadron Collider (LHC). The size of the sample corresponds to an integrated luminosity of 78 nb-1. Jets constructed with different techniques are used as input for calculating event-shape variables, which probe the structure of the hadronic final state. Normalized event-shape distributions are shown to be robust against various sources of systematic uncertainty. It is demonstrated that these early measurements of event-shape variables are sensitive to differences in the modeling of QCD multi-jet production.

Approved Plots from PAS QCD-10-013 ( click on plot to get .pdf )

Figure Abbreviated Caption
Figure_001-a.gifFigure_001-c.gif Figure_001-b.gifFigure_001-d.gif The central transverse thrust (left) and central thrust minor (right) distributions for calorimeter jets in events with leading jet pT>60 GeV/c. The bars represent the statistical uncertainty on the data, and the yellow bands represent the sum of statistical and systematic errors. Bottom plots show the ratio between data and the different simulation samples, including the jet resolution uncertainty on Monte Carlo simulations.
Figure_002-a.gifFigure_002-c.gif Figure_002-b.gifFigure_002-d.gif The central transverse thrust (left) and central thrust minor (right) distributions for calorimeter jets in events with leading jet pT>90 GeV/c. The bars represent the statistical uncertainty on the data, and the yellow bands represent the sum of statistical and systematic errors. Bottom plots show the ratio between data and the different simulation samples, including the jet resolution uncertainty on Monte Carlo simulations.
Figure_003.gif Comparison between calorimeter jets and the three other types of jet reconstruction for the central transverse thrust (left) and central thrust minor (right) distributions in data events with leading jet pT>60 GeV/c. The bars represent the statistical uncertainty on the data, and the yellow bands represent the sum of statistical and systematic errors.
Figure_004-a.gif Figure_004-b.gif The effect of absolute jet energy scale uncertainty on the central transverse thrust (left) and central thrust minor (right) distributions for calorimeter jets in events with leading jet pT>60 GeV/c.
Figure_005-a.gifFigure_005-c.gif Figure_005-b.gifFigure_001-d.gif The central transverse thrust (left) and central thrust minor (right) distributions for calorimeter jets, in events with two selected jets (top) and three or more selected jets (bottom) with leading jet pT>60 GeV/c. The bars represent the statistical error on the data, and the yellow bands represent the sum of statistical and systematic errors.

Link to QCD-10-013 PAS in CDS

-- MatthiasWeber - 09-Aug-2010

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Topic revision: r7 - 2012-09-21 - JeffreyBerryhill
 
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