PhysicsResultsFWD11003 < CMSPublic

---++!! *Study of the underlying event at forward rapidity in pp collisions at &#8730;s = 0.9, 2.76, and 7 !TeV*

%TOC{title="Contents:"}%

---++ *Abstract*
The underlying event activity in proton-proton collisions at forward pseudorapidity (%$-6.6 &lt; \eta &lt; -5.2$%) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/d&#951;, for events with a charged-particle jet produced at central pseudorapidity (%$ \vert\eta^{\rm{jet}}\vert &lt; 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}}$%, at three different pp centre-of-mass energies ( &#8730;s = 0.9, 2.76, and 7 !TeV). In addition, the &#8730;s evolution of the forward energy density is studied in inclusive events and in events with a central jet. The results are compared to those of Monte Carlo event generators for pp collisions and are discussed in terms of the underlying event. Whereas the dependence of the forward energy density ratio on jet %$p_{\rm{T}}$% at each &#8730;s separately can be well reproduced by some models, all models fail to simultaneously describe the increase of the forward energy &#65532;&#65532;density with &#8730;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)
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| *Figure* |
| [[%ATTACHURL%/PtPlots.pdf][<img src="%ATTACHURLPATH%/UE_forward_fwd11003.png" alt="PtPlots.png" height='350' />]] | 
| Ratio of the energy deposited in the pseudorapidity range %$-6.6 &lt; \eta &lt; -5.2$% for events with a charged-particle jet with %$ \vert\eta^{\rm{jet}}\vert &lt; 2$% with respect to the energy in inclusive events, as a function of the jet transverse momentum %$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 uncertainty on the data points, while the grey band represents the statistical and systematic uncertainties added in quadrature. |

| [[%ATTACHURL%/CmPlots.pdf][<img src="%ATTACHURLPATH%/CmPlots.png" alt="CmPlots.png" height='500' />]] |
| Energy density in the pseudorapidity range %$-6.6 &lt; \eta &lt; -5.2$% in inclusive events (left) and in events with a charged-particle jet in the range %$ \vert\eta^{\rm{jet}}\vert &lt; 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 uncertainties are smaller than the marker size, while the grey band 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)
%TABLE{ datavalign="middle" }%
| *Figure* |
| [[%ATTACHURL%/PtPlots_cosmicray.pdf][<img src="%ATTACHURLPATH%/PtPlots_cosmicray.png" alt="PtPlots_cosmicray.png" height='500' />]] | 
| Ratio of the energy deposited in the pseudorapidity range %$-6.6 &lt; \eta &lt; -5.2$% for events with a charged-particle jet with %$ \vert\eta^{\rm{jet}}\vert &lt; 2$% with respect to the energy in inclusive events, as a function of the jet transverse momentum %$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 uncertainty on the data points, while the grey band represents the statistical and systematic uncertainties added in quadrature. |

| [[%ATTACHURL%/CmPlots_cosmicray.pdf][<img src="%ATTACHURLPATH%/CmPlots_cosmicray.png" alt="CmPlots_cosmicray.png" height='500' />]] |
| Energy density in the pseudorapidity range %$-6.6 &lt; \eta &lt; -5.2$% in inclusive events (left) and in events with a charged-particle jet in the range %$ \vert\eta^{\rm{jet}}\vert &lt; 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 uncertainties are smaller than the marker size, while the grey band represents the statistical and systematic uncertainties added in quadrature. |

---++ *Comparisons to PYTHIA and HERWIG predictions (extra public material)* (click on plot to get .pdf)
%TABLE{ datavalign="middle" }%
| *Figure* |
| [[%ATTACHURL%/PtPlots_extra.pdf][<img src="%ATTACHURLPATH%/PtPlots_extra.png" alt="PtPlots_extra.png" height='500' />]] | 
| Ratio of the energy deposited in the pseudorapidity range %$-6.6 &lt; \eta &lt; -5.2$% for events with a charged-particle jet with %$ \vert\eta^{\rm{jet}}\vert &lt; 2$% with respect to the energy in inclusive events, as a function of the jet transverse momentum %$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 uncertainty on the data points, while the grey band represents the statistical and systematic uncertainties added in quadrature. |

| [[%ATTACHURL%/CmPlots_extra.pdf][<img src="%ATTACHURLPATH%/CmPlots_extra.png" alt="CmPlots_extra.png" height='500' />]] |
| Energy density in the pseudorapidity range %$-6.6 &lt; \eta &lt; -5.2$% in inclusive events (left) and in events with a charged-particle jet in the range %$ \vert\eta^{\rm{jet}}\vert &lt; 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 uncertainties are smaller than the marker size, while the grey band represents the statistical and systematic uncertainties added in quadrature. |

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

%TABLE{ datavalign="middle" }%
| *Figure* | *Caption* |
| [[%ATTACHURL%/cutlines_7TeV.pdf][<img src="%ATTACHURLPATH%/cutlines_7TeV.png" alt="cutlines_7TeV.png" width='500' height='486' />]] | %$\log_{10}(\xi_{\rm{Y}})$% 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. |

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who
pdf	CmPlots_cosmicray.pdf	r1	manage	16.7 K	2013-02-13 - 17:14	HansVanHaevermaet
png	CmPlots_cosmicray.png	r1	manage	91.2 K	2013-02-13 - 17:13	HansVanHaevermaet
pdf	CmPlots_extra.pdf	r1	manage	16.7 K	2013-02-14 - 10:55	HansVanHaevermaet
png	CmPlots_extra.png	r1	manage	91.7 K	2013-02-14 - 10:54	HansVanHaevermaet
pdf	CmPlots.pdf	r1	manage	16.6 K	2013-02-13 - 17:15	HansVanHaevermaet
png	CmPlots.png	r1	manage	92.4 K	2013-02-13 - 17:13	HansVanHaevermaet
pdf	cutlines_7TeV.pdf	r1	manage	698.0 K	2012-03-26 - 20:46	BenoitRoland
png	cutlines_7TeV.png	r1	manage	54.3 K	2012-03-26 - 20:49	BenoitRoland
pdf	PtPlots_cosmicray.pdf	r1	manage	23.9 K	2013-02-13 - 17:15	HansVanHaevermaet
png	PtPlots_cosmicray.png	r1	manage	119.7 K	2013-02-13 - 17:14	HansVanHaevermaet
pdf	PtPlots_extra.pdf	r1	manage	23.9 K	2013-02-14 - 10:55	HansVanHaevermaet
png	PtPlots_extra.png	r1	manage	119.5 K	2013-02-14 - 10:55	HansVanHaevermaet
pdf	PtPlots.pdf	r1	manage	23.8 K	2013-02-13 - 17:15	HansVanHaevermaet
png	PtPlots.png	r1	manage	122.1 K	2013-02-13 - 17:14	HansVanHaevermaet
png	UE_forward_fwd11003.png	r1	manage	113.5 K	2013-03-20 - 14:28	DavidDEnterria

This topic: CMSPublic > PhysicsResultsFWD11003
Topic revision: r5 - 2016-04-08 - BenoitRoland

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