# Measurement of the underlying event activity using charged particle jets in proton-proton collisions at √s = 2.76 TeV

Contents:

## Abstract

A measurement of the underlying event (UE) activity in proton-proton collisions is performed using events with a leading charged particle jet produced at central pseudo rapidity () and of transverse momentum in the range of 1 to 100 GeV. The analysis uses 0.3 of integrated luminosity at the centre-of-mass energy of 2.76 TeV at the LHC by the CMS experiment. The UE activity is measured as a function of in terms of the average multiplicity and scalar- sum of charged particles with and GeV in the azimuthal region transverse to the leading jet direction. By dividing the transverse region into the minimum and maximum activity sides with respect to the leading jet, further information on the dynamics of the UE is obtained. The measurements are compared to previous results at 0.9 and 7 TeV and to predictions of several QCD-inspired models providing constraints for the tuning parameters involved.

## Results at = 2.76 TeV

### Transverse densities

 PAS Plots Additional tunes Description png pdf png pdf Measured particle density in the transvers region (), as a function leading charged-particle jet . The data are compared to various Monte Carlo predictions of PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature. png pdf png pdf Measured density in the transvers region (), as a function leading charged-particle jet . The data are compared to various Monte Carlo predictions of PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature.

### TransMAX densities

 PAS Plots Additional tunes Description png pdf png pdf Measured particle density in the transMAX region with minimum activity within , as a function of leading charged-particle jet . PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature. png pdf png pdf Measured density in the transMAX region with minimum activity within , as a function of leading charged-particle jet . The data are compared to various Monte Carlo predictions of PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature.

### TransMIN densities

 PAS Plots Additional tunes Description png pdf png pdf Measured particle density in the transMIN region with minimum activity within , as a function of leading charged-particle jet . PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature. png pdf png pdf Measured density in the transMIN region with minimum activity within , as a function of leading charged-particle jet . The data are compared to various Monte Carlo predictions of PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature.

### TransDIF densities

 PAS Plots Additional tunes Description png pdf png pdf Measured difference of the activity in the transDIF region, (), between maximum and minimum activity regions for particle density as a function of leading charged-particle jet . PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature. png pdf png pdf Measured difference of the activity in the transDIF region, (), between maximum and minimum activity regions for density as a function of leading charged-particle jet . The data are compared to various Monte Carlo predictions of PYTHIA6 (version 6.426; tunes Z2* and CUETP6S1), PYTHIA8 (version 8.175; tunes 4C, CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. The ratios of MC predictions to the measurements are shown on the bottom of the figure. The inner errors correspond to the statistical uncertainties and the outer errors represent the statistical and systematic uncertainties added in quadrature.

## Comparison with = 0.9 TeV and 7 TeV data

 PAS Plots Additional tunes Description png pdf png pdf Comparison of UE activity at 0.9, 2.76 and 7 TeV for particle density as a function of leading charged-particle jet . Predictions of PYTHIA6 (version 6.426; tune Z2*), PYTHIA8 (version 8.175; tunes CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data. png pdf png pdf Comparison of UE activity at 0.9, 2.76 and 7 TeV for for density as a function of leading charged-particle jet . Predictions of PYTHIA6 (version 6.426; tune Z2*), PYTHIA8 (version 8.175; tunes CUETP8S1, Monash and CUETP8M1) and Herwig++ (version 2.7; tune UE-EE-5C) are compared to the data.

 Plot Description png pdf Distributions of events passing the minimun bias, jet20 and jet40 triggers weigthed by trigger prescales as a function of the leading jet . png pdf Comparision of track distributions for data and PYTHIA6 Z2* and PYTHIA8 4C Monte Carlo simulations. png pdf Comparision of leading track jet distributions for data and PYTHIA6 Z2* and PYTHIA8 4C Monte Carlo simulations.

Topic attachments
I Attachment History Action Size Date Who Comment
pdf CompareTriggerJetPtDist.pdf r1 manage 24.0 K 2014-11-03 - 15:41 XavierJanssen
png CompareTriggerJetPtDist.png r1 manage 23.9 K 2014-11-03 - 15:32 XavierJanssen
pdf compMCResultUnfoldNchEnergies_Preliminary.pdf r1 manage 24.1 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchEnergies_Preliminary.png r1 manage 23.4 K 2014-11-03 - 15:17 XavierJanssen
pdf compMCResultUnfoldNchEnergies_PreliminaryP8.pdf r1 manage 24.0 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchEnergies_PreliminaryP8.png r1 manage 23.4 K 2014-11-03 - 15:17 XavierJanssen
pdf compMCResultUnfoldNchFinal_Preliminary_diff.pdf r1 manage 19.1 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchFinal_Preliminary_diff.png r1 manage 23.2 K 2014-11-03 - 15:17 XavierJanssen
pdf compMCResultUnfoldNchFinal_Preliminary_max.pdf r1 manage 19.1 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchFinal_Preliminary_max.png r1 manage 23.3 K 2014-11-03 - 15:17 XavierJanssen
pdf compMCResultUnfoldNchFinal_Preliminary_min.pdf r1 manage 19.4 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchFinal_Preliminary_min.png r1 manage 23.6 K 2014-11-03 - 15:17 XavierJanssen
pdf compMCResultUnfoldNchFinal_Preliminary.pdf r1 manage 19.0 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldNchFinal_Preliminary.png r1 manage 23.2 K 2014-11-03 - 15:04 XavierJanssen
pdf compMCResultUnfoldNchFinal_PreliminaryP8_diff.pdf r1 manage 19.1 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchFinal_PreliminaryP8_diff.png r1 manage 23.0 K 2014-11-03 - 15:17 XavierJanssen
pdf compMCResultUnfoldNchFinal_PreliminaryP8_max.pdf r1 manage 19.1 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchFinal_PreliminaryP8_max.png r1 manage 23.1 K 2014-11-03 - 15:04 XavierJanssen
pdf compMCResultUnfoldNchFinal_PreliminaryP8_min.pdf r1 manage 19.3 K 2014-11-03 - 15:32 XavierJanssen
png compMCResultUnfoldNchFinal_PreliminaryP8_min.png r1 manage 23.4 K 2014-11-03 - 15:32 XavierJanssen
pdf compMCResultUnfoldNchFinal_PreliminaryP8.pdf r1 manage 19.0 K 2014-11-03 - 15:38 XavierJanssen
png compMCResultUnfoldNchFinal_PreliminaryP8.png r1 manage 23.2 K 2014-11-03 - 15:08 XavierJanssen
pdf compMCResultUnfoldPtsumEnergies_Preliminary.pdf r1 manage 23.3 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldPtsumEnergies_Preliminary.png r1 manage 23.2 K 2014-11-03 - 15:08 XavierJanssen
pdf compMCResultUnfoldPtsumEnergies_PreliminaryP8.pdf r1 manage 23.2 K 2014-11-03 - 15:38 XavierJanssen
png compMCResultUnfoldPtsumEnergies_PreliminaryP8.png r1 manage 23.5 K 2014-11-03 - 15:08 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_Preliminary_diff.pdf r1 manage 19.2 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldPtsumFinal_Preliminary_diff.png r1 manage 24.8 K 2014-11-03 - 15:08 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_Preliminary_max.pdf r1 manage 19.1 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldPtsumFinal_Preliminary_max.png r1 manage 24.4 K 2014-11-03 - 15:08 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_Preliminary_min.pdf r1 manage 19.3 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldPtsumFinal_Preliminary_min.png r1 manage 24.0 K 2014-11-03 - 15:08 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_Preliminary.pdf r1 manage 19.2 K 2014-11-03 - 15:17 XavierJanssen
png compMCResultUnfoldPtsumFinal_Preliminary.png r1 manage 24.5 K 2014-11-03 - 15:04 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_PreliminaryP8_diff.pdf r1 manage 19.2 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldPtsumFinal_PreliminaryP8_diff.png r1 manage 24.6 K 2014-11-03 - 15:04 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_PreliminaryP8_max.pdf r1 manage 19.0 K 2014-11-03 - 15:22 XavierJanssen
png compMCResultUnfoldPtsumFinal_PreliminaryP8_max.png r1 manage 24.2 K 2014-11-03 - 15:04 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_PreliminaryP8_min.pdf r1 manage 19.3 K 2014-11-03 - 15:17 XavierJanssen
png compMCResultUnfoldPtsumFinal_PreliminaryP8_min.png r1 manage 23.7 K 2014-11-03 - 15:04 XavierJanssen
pdf compMCResultUnfoldPtsumFinal_PreliminaryP8.pdf r1 manage 19.2 K 2014-11-03 - 15:38 XavierJanssen
png compMCResultUnfoldPtsumFinal_PreliminaryP8.png r1 manage 24.4 K 2014-11-03 - 15:04 XavierJanssen
pdf LeadJetPtdist_prelim.pdf r1 manage 56.2 K 2014-11-03 - 15:22 XavierJanssen
png LeadJetPtdist_prelim.png r1 manage 68.9 K 2014-11-03 - 15:04 XavierJanssen
pdf trackpt_prelim.pdf r1 manage 54.0 K 2014-11-03 - 15:22 XavierJanssen
png trackpt_prelim.png r1 manage 66.7 K 2014-11-03 - 15:04 XavierJanssen
Topic revision: r5 - 2014-11-03 - XavierJanssen

Create a LeftBar

 Cern Search TWiki Search Google Search CMSPublic All webs
Copyright &© 2008-2021 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
or Ideas, requests, problems regarding TWiki? use Discourse or Send feedback