Polarized Tops from Stop Decays at the LHC

TL;DR

This paper explores how top quark polarization from stop decays in supersymmetric models can be observed at the LHC, providing insights into stop mixing and neutralino properties relevant for understanding electroweak symmetry breaking.

Contribution

It introduces the concept of an effective stop mixing angle and discusses its potential measurement at the LHC to probe supersymmetric parameters.

Findings

Top polarization in stop decays can be observable at the LHC.

Measurement of the effective stop mixing angle is feasible with realistic data.

This measurement can constrain neutralino mixing and inform naturalness in MSSM.

Abstract

In supersymmetric models, scalar top quarks, or stops, generically have parity-violating couplings to top quarks. As a result, tops produced in stop decays should be polarized. In this paper, we will argue that this effect may be observable at the LHC with realistic integrated luminosities, provided that one of the stops is copiously produced and can decay to a top and a neutralino. We define the "effective" stop mixing angle, which determines the degree of top polarization, and discuss the prospects for a measurement of this angle at the LHC. If some information about the neutralino mixing matrix is available, this measurement can be used to constrain the mixing angle in the stop sector, one of the most important ingredients in assessing the naturalness of electroweak symmetry breaking in the MSSM.