The top-quark decay vertex in standard model extensions

Abstract

New physics interactions can affect the strength and structure of the tbW vertex. We investigate the magnitudes and phases of "anomalous" contributions to this vertex in a two-Higgs doublet and the minimal supersymmetric extension of the standard model, and in a top-color assisted technicolor (TC2) model. While the magnitudes of the anomalous couplings remain below 1 percent in the first two models, TC2 interactions can reduce the left-chiral coupling f L by several percent.

Summary of the CKM 2016 working group on high-energy flavor physics

“…Since the top quark decays before hadronization, its polarization is amenable to measurement and can be compared to the SM prediction [15]. Possible deviations from SM can be interpreted either in the context of specific theories [16,17], or in the context of effective field theories (see Sec. 7).…”

Probing the top-quark width through ratios of resonance contributions of e + e − → W + W − b b ¯ $$ {\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{W}}^{+}{\mathrm{W}}^{-}\mathrm{b}\overline{\mathrm{b}} $$

“…The coupling g tbW can be altered in models beyond the SM -we direct the interested reader to refs. [55,56] for concrete examples in the context of a 2-Higgs-Doublet Model, the Minimal Supersymmetric Standard Model or top-color assisted Technicolor. Their effects are most dominant in the left-handed part of the coupling g tbW and are in the range of a few percent.…”

Using single top rapidity to measureVtd,Vts,VAguilar-Saavedra1, Onofre2 2011Phys. Rev. D10040View full textAdd to dashboardCite

“…These anomalous contributions, expected to be most important for the W tb vertex [12], can also be included in the fit in a straightforward way by extending the set of observables [13]. We also ignore possible new physics contributions from four-fermion operators [14].…”