Asymmetry Observables for Measuring Spin Correlations in Top-Quark Pair Production

Abstract

Spin correlations between top-quark and anti-top-quark in pair production are sensitive to physics beyond the standard model. A complete set of observables, that can be used to measure all independent parameters of the production spin density matrix, is necessary to search for anomalous interactions in the production dynamics. In this letter, we provide a set of asymmetry observables for measuring all the density matrix elements. These observables are defined regardless of the production mechanism, and can be specified in any desired reference frame, particularly the laboratory frame in which the first evidence of spin correlation was observed experimentally. Our method can be used to find an optimal Lorentz frame in which the sensitivity to the density matrices is high for given production process and experimental environment, or to test possible correlations among the matrix elements.

6 pages; v2: typos are corrected; v3: the title, abstract and writing logical are changed. Two more observables are added; v4: text are improved

References in corpus (8)

• Combined Measurement of the Higgs Boson Mass in $pp$ Collisions at $\sqrt{s}=7$ and 8 TeV with the ATLAS and CMS Experiments
• Why should we care about the top quark Yukawa coupling?
• Spin Correlation Effects in Top Quark Pair Production at the LHC
• Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at $\sqrt{s}=8$ TeV Using the ATLAS Detector
• On measurement of top polarization as a probe of $t\bar{t}$ production mechanisms at the LHC
• Asymmetries in top quark pair production at hadron colliders
• Measurements of spin correlation in top-antitop quark events from proton-proton collisions at $\sqrt{s}=7$ TeV using the ATLAS detector
• Data driving the top quark forward--backward asymmetry with a lepton-based handle