Z '-induced FCNC decays of top, beauty, and strange quarks
Journal
Physical Review D
Journal Volume
2019
Journal Issue
1
Pages
54021
Date Issued
2019
Author(s)
Abstract
Anomalous b→s transitions from LHCb data may suggest a new massive gauge boson Z′ that couples to the left-handed b→s current, which in turn implies a coupling to the t→c current. In this paper, we study flavor-changing neutral current (FCNC) decays of the top quark induced by a Z′ boson, namely t→cZ′, based on a model of the gauged Lμ-Lτ symmetry (the difference between the muon and tauon numbers) with vectorlike quarks, which was introduced to explain the anomalous LHCb data. We illustrate that searching for t→cZ′ via Z′→μ+μ- with LHC Run 1 data can probe a parameter region that is unexplored by B physics for a Z′ mass of around O(10) GeV or greater. We further extend the model to a very light Z′ with mass below 400 MeV, which is motivated by the muon g-2 anomaly. Taking rare B and K meson decay data into account, we give upper limits on the t→cZ′ branching ratio for the light Z′ case, and discuss about its observability at the LHC. We also scrutinize the possibility that the decay KL→π0Z′ with Z′→νν¯ may lead to an apparent violation of the usual Grossman-Nir bound of B(KL→π0νν¯)<1.4×10-9.
Type
journal article