[Seminars] HEP Seminar Today - Oct 19

Holly Hernandez holly2 at uchicago.edu
Mon Oct 19 08:39:13 CDT 2015


Monday October 19, 2015
ERC 401

Speaker: Max Swiatlowski (UChicago)

Title: Measuring Color Flow in Top Pair Events Using the ATLAS Detector

Abstract: Colored particles— those charged under the strong nuclear force— are not observed directly at colliders, but instead form jets: collimated sprays of color-neutral particles. This process of hadronization would seem to prevent the direct study of color, but some aspects of jets remain influenced by the color charge of their initiating patrons. In particular, the distribution and orientation of energy inside jets is predicted to be an experimental handle on color flow between the quarks and gluons initiating the jets. This talk presents a measurement of the distribution of one such variable, the jet pull angle, using \sqrt{s} = 8 TeV data from the ATLAS detector at the LHC. Top quark pair production provides a large supply of W-bosons which decay to pairs of jets. The pull angle of these jets is used to demonstrate that the W-boson is a color singlet, as expected; the data, once corrected for detector resolution and acceptance effects, can also be used to constrain various parton shower and hadronization models. With the observation of color flow effects at hadron colliders, these techniques can be extended to searching for, or characterizing, new physics and Higgs bosons in hadronic final states.

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