Better hadronic top quark polarimetry

Brock Tweedie
Phys. Rev. D 90, 094010 – Published 12 November 2014

Abstract

Observables sensitive to top-quark polarization are important for characterizing or even discovering new physics. The most powerful spin analyzer in top decay is the down-type fermion from the W, which in the case of leptonic decay allows for very clean measurements. However, in many applications it is useful to measure the polarization of hadronically decaying top quarks. Usually it is assumed that at most 50% of the spin analyzing power can be recovered in this case. This paper introduces a simple and truly optimal hadronic spin analyzer, with a power of 64% at leading order (LO). The improvement is demonstrated to be robust at next-to-leading order, and in a handful of simulated measurements including the spins and spin correlations of boosted top quarks from multi-TeV tt¯ resonances, the spins of semi-boosted tops from chiral top-squark decays, and the potentially CP-violating spin correlations induced in continuum tt¯ by color-dipole operators. For the boosted studies, we explore jet substructure techniques that exhibit improved mapping between subjets and quarks.

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  • Received 26 February 2014

DOI:https://doi.org/10.1103/PhysRevD.90.094010

© 2014 American Physical Society

Authors & Affiliations

Brock Tweedie

  • PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA

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Issue

Vol. 90, Iss. 9 — 1 November 2014

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