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-- BenoitRoland - 26-Mar-2012

Study of the underlying event at forward rapidity in pp collisions at √s = 0.9, 2.76, and 7 TeV

Abstract

The underlying event activity in proton-proton collisions at forward pseudorapidity ($-6.6 < \eta < -5.2$) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/dη, for events with a charged-particle jet produced at central pseudorapidity ($ \vert\eta^{\rm{jet}}\vert < 2$) to the forward energy density for inclusive events. This forward energy density ratio is measured as a function of the central jet transverse momentum, $p_{\rm{T}}$, at three different pp centre-of-mass energies ( √s = 0.9, 2.76, and 7 TeV). In addition, the √s evolution of the forward energy density is studied in inclusive events and in events with a central jet. The results are compared to those of Monte Carlo event generators for pp collisions and are discussed in terms of the underlying event. Whereas the dependence of the forward energy density ratio on jet $p_{\rm{T}}$ at each √s separately can be well reproduced by some models, all models fail to simultaneously describe the increase of the forward energy density with √s in both inclusive events and in events with a central jet.

Comparisons to PYTHIA and HERWIG predictions (Paper) (click on plot to get .pdf)

Figure
PtPlots.png
Ratio of the energy deposited in the pseudorapidity range $-6.6 < \eta < -5.2$ for events with a charged particle jet with $ \vert\eta^{\rm{jet}}\vert < 2$ with respect to the energy in inclusive events, as a function of charged particle jet transverse momentum $p_{\rm{T}}$ for $\sqrt{s} =$ 0.9 (left), 2.76 (middle), and 7 TeV (right). Corrected results are compared to the PYTHIA and HERWIG++ MC models. Error bars indicate the statistical error on the data points, while the grey band around data points represents the statistical and systematic uncertainties added in quadrature.

CmPlots.png
Energy density in the pseudorapidity range $-6.6 < \eta < -5.2$ in inclusive events (left) and in events with a charged-particle jet in the range $ \vert\eta^{\rm{jet}}\vert < 2$ (right) as a function of $\sqrt{s}$, normalized to the energy density at $\sqrt{s} =$ 2.76 TeV. The $p_{\rm{T}}$ threshold used for jets is 10 GeV/c at all centre-of-mass energies. Corrected results are compared to the PYTHIA and HERWIG++ MC models. Statistical errors are smaller than the markers size, while the grey band around data points represents the statistical and systematic uncertainties added in quadrature.

Comparisons to Cosmic Ray, CASCADE and DIPSY model predictions (Paper) (click on plot to get .pdf)

Figure
PtPlots_cosmicray.png
Ratio of the energy deposited in the pseudorapidity range $-6.6 < \eta < -5.2$ for events with a charged particle jet with $ \vert\eta^{\rm{jet}}\vert < 2$ with respect to the energy in inclusive events, as a function of charged particle jet transverse momentum $p_{\rm{T}}$ for $\sqrt{s} =$ 0.9 (left), 2.76 (middle), and 7 TeV (right). Corrected results are compared to MC models used in cosmic ray physics and to CASCADE and DIPSY. Error bars indicate the statistical error on the data points, while the grey band around data points represents the statistical and systematic uncertainties added in quadrature.

CmPlots_cosmicray.png
Energy density in the pseudorapidity range $-6.6 < \eta < -5.2$ in inclusive events (left) and in events with a charged-particle jet in the range $ \vert\eta^{\rm{jet}}\vert < 2$ (right) as a function of $\sqrt{s}$, normalized to the energy density at $\sqrt{s} =$ 2.76 TeV. The $p_{\rm{T}}$ threshold used for jets is 10 GeV/c at all centre-of-mass energies. Corrected results are compared to MC models used in cosmic ray physics and to CASCADE and DIPSY. Statistical errors are smaller than the markers size, while the grey band around data points represents the statistical and systematic uncertainties added in quadrature.

Comparisons to PYTHIA and HERWIG predictions (extra public material) (click on plot to get .pdf)

Detector level cuts versus particle level $\xi$ selection (extra public material) (click on plot to get .pdf)

Figure Caption
cutlines_7TeV.png $\log_{10}(\xi_{\rm{Y}})$ vs. $\log_{10}(\xi_{\rm{X}})$ for all generated events (orange) and for generated events selected at the detector level (blue) for $\sqrt{s} =$ 7 TeV. Single diffractive dissociation events have a $\xi_{\rm{X}}$ or $\xi_{\rm{Y}}$ value equal to $m_p^2/s$ ($\approx 10^{-7.7}$ at $\sqrt{s} =$ 7 TeV), while double diffractive dissociation and non-diffractive events have $\xi_{\rm{X}}$ and $\xi_{\rm{Y}}$ values ranging from 0 to 1. The green lines indicate the particle level cuts. At the particle level, all events to the top and to the right of the green lines are selected.
Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf CmPlots.pdf r1 manage 16.6 K 2013-02-13 - 17:15 HansVanHaevermaet  
PNGpng CmPlots.png r1 manage 92.4 K 2013-02-13 - 17:13 HansVanHaevermaet  
PDFpdf CmPlots_cosmicray.pdf r1 manage 16.7 K 2013-02-13 - 17:14 HansVanHaevermaet  
PNGpng CmPlots_cosmicray.png r1 manage 91.2 K 2013-02-13 - 17:13 HansVanHaevermaet  
PDFpdf PtPlots.pdf r1 manage 23.8 K 2013-02-13 - 17:15 HansVanHaevermaet  
PNGpng PtPlots.png r1 manage 122.1 K 2013-02-13 - 17:14 HansVanHaevermaet  
PDFpdf PtPlots_cosmicray.pdf r1 manage 23.9 K 2013-02-13 - 17:15 HansVanHaevermaet  
PNGpng PtPlots_cosmicray.png r1 manage 119.7 K 2013-02-13 - 17:14 HansVanHaevermaet  
PDFpdf Ratio_vs_pt_corrected_2760GeV_cosmicray_public.pdf r1 manage 16.5 K 2012-03-26 - 19:48 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_2760GeV_cosmicray_public.png r1 manage 16.5 K 2012-03-26 - 19:49 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_2760GeV_extra_public.pdf r1 manage 16.6 K 2012-03-26 - 20:11 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_2760GeV_extra_public.png r1 manage 17.1 K 2012-03-26 - 20:12 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_2760GeV_public.pdf r1 manage 16.5 K 2012-03-26 - 18:29 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_2760GeV_public.png r1 manage 16.9 K 2012-03-26 - 18:30 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_7TeV_cosmicray_public.pdf r1 manage 16.5 K 2012-03-26 - 19:48 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_7TeV_cosmicray_public.png r1 manage 17.4 K 2012-03-26 - 19:49 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_7TeV_extra_public.pdf r1 manage 16.6 K 2012-03-26 - 20:11 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_7TeV_extra_public.png r1 manage 17.7 K 2012-03-26 - 20:13 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_7TeV_public.pdf r1 manage 16.4 K 2012-03-26 - 18:30 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_7TeV_public.png r1 manage 17.8 K 2012-03-26 - 18:31 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_900GeV_cosmicray_public.pdf r1 manage 16.5 K 2012-03-26 - 19:48 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_900GeV_cosmicray_public.png r1 manage 16.7 K 2012-03-26 - 19:49 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_900GeV_extra_public.pdf r1 manage 16.7 K 2012-03-26 - 20:11 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_900GeV_extra_public.png r1 manage 17.5 K 2012-03-26 - 20:12 BenoitRoland  
PDFpdf Ratio_vs_pt_corrected_900GeV_public.pdf r1 manage 16.5 K 2012-03-26 - 18:29 BenoitRoland  
PNGpng Ratio_vs_pt_corrected_900GeV_public.png r1 manage 17.2 K 2012-03-26 - 18:30 BenoitRoland  
PDFpdf RelativeEflow_vs_cmenergy_cosmicray_public.pdf r1 manage 14.0 K 2012-03-26 - 19:48 BenoitRoland  
PNGpng RelativeEflow_vs_cmenergy_cosmicray_public.png r1 manage 13.5 K 2012-03-26 - 19:49 BenoitRoland  
PDFpdf RelativeEflow_vs_cmenergy_extra_public.pdf r1 manage 14.1 K 2012-03-26 - 20:12 BenoitRoland  
PNGpng RelativeEflow_vs_cmenergy_extra_public.png r1 manage 14.4 K 2012-03-26 - 20:13 BenoitRoland  
PDFpdf RelativeEflow_vs_cmenergy_public.pdf r1 manage 14.0 K 2012-03-26 - 18:30 BenoitRoland  
PNGpng RelativeEflow_vs_cmenergy_public.png r1 manage 14.1 K 2012-03-26 - 18:31 BenoitRoland  
PDFpdf RelativeLeadingjetEflow_vs_cmenergy_cosmicray_public.pdf r1 manage 14.1 K 2012-03-26 - 19:49 BenoitRoland  
PNGpng RelativeLeadingjetEflow_vs_cmenergy_cosmicray_public.png r1 manage 14.8 K 2012-03-26 - 19:50 BenoitRoland  
PDFpdf RelativeLeadingjetEflow_vs_cmenergy_extra_public.pdf r1 manage 14.2 K 2012-03-26 - 20:12 BenoitRoland  
PNGpng RelativeLeadingjetEflow_vs_cmenergy_extra_public.png r1 manage 15.7 K 2012-03-26 - 20:13 BenoitRoland  
PDFpdf RelativeLeadingjetEflow_vs_cmenergy_public.pdf r1 manage 14.1 K 2012-03-26 - 18:30 BenoitRoland  
PNGpng RelativeLeadingjetEflow_vs_cmenergy_public.png r1 manage 15.6 K 2012-03-26 - 18:31 BenoitRoland  
PDFpdf cutlines_7TeV.pdf r1 manage 698.0 K 2012-03-26 - 20:46 BenoitRoland  
PNGpng cutlines_7TeV.png r1 manage 54.3 K 2012-03-26 - 20:49 BenoitRoland  
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Topic revision: r2 - 2013-02-13 - HansVanHaevermaet
 
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