Measurement of the K(T) Distribution of Particles in Jets Produced in P Anti-p Collisions at S**ư

Measurement of the K(T) Distribution of Particles in Jets Produced in P Anti-p Collisions at S**ư
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Total Pages: 7
Release: 2008
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We present a measurement of the transverse momentum with respect to the jet axis (k{sub T}) of particles in jets produced in p{bar p} collisions at √s = 1.96 TeV. Results are obtained for charged particles within a cone of opening angle 0.5 radians around the jet axis in events with dijet invariant masses between 66 and 737 GeV/c2. The experimental data are compared to theoretical predictions obtained for fragmentation partons within the framework of resummed perturbative QCD using the modified leading log and next-to-modified leading log approximations. The comparison shows that trends in data are successfully described by the theoretical predictions, indicating that the perturbative QCD stage of jet fragmentation is dominant in shaping basic jet characteristics.

Measurement of the K(T) Distribution of Particles in Jets Produced in P Anti-p Collisions at S**1/2

Measurement of the K(T) Distribution of Particles in Jets Produced in P Anti-p Collisions at S**1/2
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Total Pages: 7
Release: 2008
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We present a measurement of the transverse momentum with respect to the jet axis (k{sub T}) of particles in jets produced in p{bar p} collisions at √s = 1.96 TeV. Results are obtained for charged particles within a cone of opening angle 0.5 radians around the jet axis in events with dijet invariant masses between 66 and 737 GeV/c2. The experimental data are compared to theoretical predictions obtained for fragmentation partons within the framework of resummed perturbative QCD using the modified leading log and next-to-modified leading log approximations. The comparison shows that trends in data are successfully described by the theoretical predictions, indicating that the perturbative QCD stage of jet fragmentation is dominant in shaping basic jet characteristics.

Fragmentation of Jets Produced in Proton-Antiproton Collisions at $\sqrt{s}

Fragmentation of Jets Produced in Proton-Antiproton Collisions at $\sqrt{s}
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Total Pages: 140
Release: 2007
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We present the first measurement of two-particle momentum correlations in jets produced in p$\bar{p}$ collisions at center of mass energy of 1.96 TeV. A comparison of the experimental data to theoretical predictions obtained for partons within the framework of resummed perturbative QCD (Next-to-Leading Log Approximation) shows that the predicted parton momentum correlations survive the hadronization stage of jet fragmentation and are present at the hadron level. We also present the measurement of the intrinsic transverse momenta of particles with respect to jet axis (kT). Experimental data is compared to the theoretical predictions obtained for partons within the framework of Modified Leading Log Approximation and Next-to-Modified Leading Log Approximation, and shows good agreement in the range of validity of the theoretical predictions. The results of both measurements indicate that the perturbative stage of the jet formation must be dominant and give further support to the hypothesis of Local Parton-Hadron Duality.

A Measurement of the Underlying Event Distributions in Proton-Proton Collisions at Sqrt(s)

A Measurement of the Underlying Event Distributions in Proton-Proton Collisions at Sqrt(s)
Author: Joseph Salvatore Virzi
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Total Pages: 184
Release: 2012
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Underlying Event distributions are studied in events containing at least one charged particle jet produced in proton-proton collisions at sqrt(s) = 7 TeV. Jets are reconstructed from charged particles using the anti-Kt algorithm with radius parameter R = 0.6. The jet with the largest transverse momentum (pT) and.

Modification of Jet Shapes in PbPb Collisions at $\sqrt {s_{NN}}

Modification of Jet Shapes in PbPb Collisions at $\sqrt {s_{NN}}
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Total Pages: 21
Release: 2014
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The first measurement of jet shapes, defined as the fractional transverse momentum radial distribution, for inclusive jets produced in heavy-ion collisions is presented. Data samples of PbPb and pp collisions, corresponding to integrated luminosities of 150 inverse microbarns and 5.3 inverse picobarns respectively, were collected at a nucleon-nucleon centre-of-mass energy of sqrt(s[NN]) = 2.76 TeV with the CMS detector at the LHC. The jets are reconstructed with the anti-kt algorithm with a distance parameter R=0.3, and the jet shapes are measured for charged particles with transverse momentum pt> 1 GeV. The jet shapes measured in PbPb collisions in different collision centralities are compared to reference distributions based on the pp data. A centrality-dependent modification of the jet shapes is observed in the more central PbPb collisions, indicating a redistribution of the energy inside the jet cone. This measurement provides information about the parton shower mechanism in the hot and dense medium produced in heavy-ion collisions.

Reconstruction and Attributes of Jets Observed in [square Root of S]

Reconstruction and Attributes of Jets Observed in [square Root of S]
Author: Thomas William Henry
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Release: 2007
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The STAR collaboration recorded [square root of s] =200 GeV per nucleon d+Au and p+pcollision events during the year 2003 RHIC run. In the p+p and the d+Au data samples, itis possible to reconstruct jets and make comparisons between them. This dissertation describes the reconstructed jet sample from the p+p events, the measurements of the jet jT distribution which quantifies the shape of the jet perpendicular to the jet direction, the jet fragmentation function (z), which quantifies the fraction of jet momentum carried by the jet particles, and the width of the parton momentum broadening distribution (kT). This dissertation also describes the comparison of these results to the reconstructed jet sample from d+Au events. Measurements of jet jT and jet fragmentation from p+p, d+Au, and PYTHIA are compared. The z and jT distributions from p+p and also d+Au are found to be consistent with PYTHIA event simulation version 6.205. RMS (jT) equals 612"12"30 MeV/c for p+p, and RMS (jT) equals 630"13"30 MeV/c for d+Au. The p+p kT Gaussian sigma (width) equals 2.08"0.12"0.13 GeV/c. This width is consistent with PYTHIA, kT literature surveys, and other RHIC measurements. A limit on nuclear kT broadening in the Au nucleus is also obtained, showing that nuclear kT is consistent with zero to within 0.5 GeV/c. The present status of the RdAu measurement from jets is also described. The nuclear kT broadening, in particular, is a measurement which has been done at this energy for the first time at RHIC. These measurements, while interesting by themselves, also will contribute ultimately to the understanding of Au+Au collisions at RHIC, and the properties of the high-density matter which results from them.