# Measurement of the inclusive forward-backward t$\bar{t}$ production asymmetry and its rapidity dependence dA<sub>fb</sub>/d(Δy)

### Description

Early measurements of a large forward-background asymmetry at the CDF and D0 experiments at Fermilab have generated much recent interest, but were hampered by large uncertainties. We present here a new measurement of the parton level forward-backward asymmetry of pair-produced top quarks, using a high-statistics sample with much improved precision. We study the rapidity, y<sub>top</sub>, of the top quark production angle with respect to the incoming parton momentum in both the lab and t$\bar{t}$ rest frames. We find the parton-level forward-backward asymmetries to be A<sub>fb</sub><sup>p$\bar{t}$</sup> = 0.150 ± 0.050<sup>stat</sup> ± 0.024<sup>syst</sup> A<sub>fb</sub><sup>t$\bar{t}$</sup> = 0.158 ± 0.072{sup stat} ± 0.024<sup>syst</sup>. These ... continued below

140 p.

### Creation Information

Strycker, Glenn Loyd January 1, 2010.

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### Description

Early measurements of a large forward-background asymmetry at the CDF and D0 experiments at Fermilab have generated much recent interest, but were hampered by large uncertainties. We present here a new measurement of the parton level forward-backward asymmetry of pair-produced top quarks, using a high-statistics sample with much improved precision. We study the rapidity, y<sub>top</sub>, of the top quark production angle with respect to the incoming parton momentum in both the lab and t$\bar{t}$ rest frames. We find the parton-level forward-backward asymmetries to be A<sub>fb</sub><sup>p$\bar{t}$</sup> = 0.150 ± 0.050<sup>stat</sup> ± 0.024<sup>syst</sup> A<sub>fb</sub><sup>t$\bar{t}$</sup> = 0.158 ± 0.072{sup stat} ± 0.024<sup>syst</sup>. These results should be compared with the small p$\bar{p}$ frame charge asymmetry expected in QCD at NLO, A<sub>fb</sub> = 0.050 ± 0.015. Additionally, we introduce a measurement of the A<sub>fb</sub> rapidity dependence dA<sub>fb</sub>/d(Δy). We find this to be A<sub>fb</sub><sup>p$\bar{t}$</sup>(|Δy| &lt; 1.0) = 0.026 ± 0.104<sup>stat</sup> ± 0.012 <sup>syst</sup> A<sub>fb</sub><sup>p$\bar{t}$</sup>(|Δy| &gt; 1.0) = 0.611 ± 0.210<sup>stat</sup> ± 0.246<sup>syst</sup> which we compare with model predictions 0.039 ± 0.006 and 0.123 ± 0.018 for the inner and outer rapidities, respectively.

140 p.

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• Report No.: FERMILAB-THESIS--2010-37
• Grant Number: AC02-07CH11359
• DOI: 10.2172/988435 | External Link
• Office of Scientific & Technical Information Report Number: 988435

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#### Office of Scientific & Technical Information Technical Reports

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### Creation Date

• January 1, 2010

### Added to The UNT Digital Library

• Oct. 14, 2017, 8:36 a.m.

### Description Last Updated

• Oct. 24, 2017, 2:59 p.m.

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Strycker, Glenn Loyd. Measurement of the inclusive forward-backward t$\bar{t}$ production asymmetry and its rapidity dependence dA<sub>fb</sub>/d(Δy), thesis or dissertation, January 1, 2010; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc1014971/: accessed November 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.