Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ with the ATLAS detector

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Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy $\sqrt{s} = 7 TeV$ with the ATLAS detector

G. Aad et al. (ATLAS Collaboration)

Phys. Rev. D 84, 054001 – Published 20 September 2011

Abstract

Jets are identified and their properties studied in center-of-mass energy $\sqrt{s} = 7 TeV$ proton-proton collisions at the Large Hadron Collider using charged particles measured by the ATLAS inner detector. Events are selected using a minimum bias trigger, allowing jets at very low transverse momentum to be observed and their characteristics in the transition to high-momentum fully perturbative jets to be studied. Jets are reconstructed using the anti- $k_{t}$ algorithm applied to charged particles with two radius parameter choices, 0.4 and 0.6. An inclusive charged jet transverse momentum cross section measurement from 4 GeV to 100 GeV is shown for four ranges in rapidity extending to 1.9 and corrected to charged particle-level truth jets. The transverse momenta and longitudinal momentum fractions of charged particles within jets are measured, along with the charged particle multiplicity and the particle density as a function of radial distance from the jet axis. Comparison of the data with the theoretical models implemented in existing tunings of Monte Carlo event generators indicates reasonable overall agreement between data and Monte Carlo. These comparisons are sensitive to Monte Carlo parton showering, hadronization, and soft physics models.

Received 17 July 2011

DOI:https://doi.org/10.1103/PhysRevD.84.054001

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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Vol. 84, Iss. 5 — 1 September 2011

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Figure 1
The cross section for anti- $k_{t}$ charged particle jets as a function of $p_{T}$ , with $| y | < 0.5$ and radius parameter $R$ as indicated. The shaded area is the total uncertainty for the corrected data distribution, excluding the overall 3.4% luminosity uncertainty. The data are compared to a range of theoretical results from Monte Carlo event generators, which are normalized to the data over the full momentum and rapidity range measured, using the scale factor $S$ as defined in the text. The bottom inserts show the fractional difference between these distributions and the data. The distributions for the Perugia HARD (Perugia SOFT) tune, not shown, agree qualitatively with the Perugia 2010 (Perugia 0) tune.
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Figure 2
The cross section for anti- $k_{t}$ charged particle jets as a function of rapidity, for selected momentum bins and radius parameter $R$ as indicated. The shaded area is the total uncertainty for the corrected data distribution, excluding the overall 3.4% luminosity uncertainty. The data are compared to a range of theoretical results from Monte Carlo event generators, which are normalized to the data separately for each momentum range. The distributions for all Perugia samples agree qualitatively, so only Perugia 0 is shown. The two Herwig++ tunes agree, so only Herwig++ 2.4.2 is shown.
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Figure 3
Multiplicity of particles per charged particle jet, over the full measured rapidity range $| y | < 1.9$ , with anti- $k_{t}$ radius parameter $R$ as indicated. Figure 3 (c) shows the distributions for five momentum ranges with $R = 0.4$ (0.6), and Fig. 3 (d) shows the fractional difference between a range of Monte Carlo event generator predictions and the data. The distributions for the Perugia 2010 tune, not shown, agree qualitatively with the Perugia 0 tune.
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Figure 4
The distribution of the fragmentation variable $z$ for anti- $k_{t}$ jets with radius parameter $R$ as indicated, in the rapidity range $| y | < 1.9$ . Figure 4 (c) shows the distributions for five momentum ranges with $R = 0.4$ (0.6), and Fig. 4 (d) shows the fractional difference between a range of Monte Carlo event generator predictions and the data. The distributions for the Perugia 2010 (Perugia SOFT) tune, not shown, agree qualitatively with the Perugia 0 (AMBT1) tune.
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Figure 5
The distribution of the charged particle transverse momentum $p_{T}^{rel}$ with respect to anti- $k_{t}$ jets with radius parameter $R$ as indicated, in the rapidity range $| y | < 1.9$ . Figure 5 (c) shows the distributions for five momentum ranges with $R = 0.4$ (0.6), and Fig. 5 (d) shows the fractional difference between a range of Monte Carlo event generator predictions and the data.
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Figure 6
The distribution of the charged particle number density $ρ_{ch} (r)$ for anti- $k_{t}$ jets with radius parameter $R$ as indicated, in the rapidity range $| y | < 1.9$ . Figure 6(c) shows the distributions for five momentum ranges with $R = 0.4$ (0.6), and Fig. 6 (d) shows the fractional difference between a range of Monte Carlo event generator predictions and the data.
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Physical Review D

covering particles, fields, gravitation, and cosmology

Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy $\sqrt{s} = 7 TeV$ with the ATLAS detector

G. Aad et al. (ATLAS Collaboration)

Phys. Rev. D 84, 054001 – Published 20 September 2011

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Physical Review D

covering particles, fields, gravitation, and cosmology

Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy s=7 TeV with the ATLAS detector

G. Aad et al. (ATLAS Collaboration)

Phys. Rev. D 84, 054001 – Published 20 September 2011

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Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy $\sqrt{s} = 7 TeV$ with the ATLAS detector