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General Tests for t ---> W+ b couplings at Hadron Colliders

High Energy Physics - Phenomenology 2009-10-30 v3

Abstract

The modularity property of the helicity formalism is used to provide amplitude expressions and stage-two spin-correlation functions which can easily be used in direct experimental searches for electro-weak symmetries and dynamics in the decay processes tW+bt \to W^+ b, tˉWbˉ\bar t \to W^- \bar b. The formalism is used to describe the decay sequences tW+b(l+ν)bt\to W^{+}b\to (l^{+}\nu)b, and tW+b(jdˉju)bt\to W^{+}b\to (j_{\bar d}j_u)b. Helicity amplitudes for tW+bt \to W^+ b are obtained for the most general JbˉtJ_{\bar b t} current. Thereby, the most general Lorentz-invariant decay-density-matrix for tW+b(l+ν)bt\to W^{+}b\to (l^{+}\nu)b, or for tW+b(jdˉju)bt\to W^{+}b\to (j_{\bar d}j_u)b, is expressed in terms of eight helicity parameters and, equivalently, in terms of the structures of the JbˉtJ_{\bar b t} current. The parameters are physically defined in terms of partial-width-intensities for polarized-final-states in \newline tW+bt\to W^{+}b decay. The full angular distribution for the reactions qqˉq \bar q and ggttˉ(W+b)(Wbˉ)...g g \to t \bar t \to (W^+ b) (W^- \bar b) \to ... can be used to measure these parameters. Since this adds on spin-correlation information from the next stage of decays in the decay sequence, such an energy-angular distribution is called a stage-two spin-correlation (S2SC) function.

Cite

@article{arxiv.hep-ph/9707211,
  title  = {General Tests for t ---> W+ b couplings at Hadron Colliders},
  author = {Charles A. Nelson and Brian T. Kress and Marco Lopes and Thomas P. McCauley},
  journal= {arXiv preprint arXiv:hep-ph/9707211},
  year   = {2009}
}

Comments

Minor clarifications. Expressions for r_{+-}, rho_{+-}, and \xi for ( L + S-P) coupling corrected. 36 pages LaTex + Tables + 14 Figs

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