[SUNY BING 12/22/00 I] hep-ph/0101303 USE OF Λb POLARIMETRY IN TOP QUARK SPIN-CORRELATION FUNCTIONS

Due to the absence of hadronization effects and the large mt mass, top quark decay will be uniquely sensitive to fundamental electroweak physics at the Tevatron, at the LHC, and at a future linear collider. A “complete measurement” of the four helicity amplitudes in t → W+b decay is possible by the combined use of Λb and W polarimetry in stage-two spincorrelation functions (S2SC). In this paper, the most general Lorentz-invariant decay density matrix is obtained for the decay sequence t → W+b where b → l−ν̄c and W+ → lνl [ or W+ → jdju ], and likewise for t̄ → W−b̄. These density matrices are expressed in terms of b-polarimetry helicity parameters which enable a unique determination of the relative phases among the A(λb, λW−) amplitudes. Thereby, S2SC distributions and single-sided distributions are expressed in terms of these parameters. The four b-polarimetry helicity parameters involving the A(−1,−1/2) amplitude are considered in detail. Λb polarimetry signatures will not be suppressed in top quark analyses when final ν̄ angles-and-energy variables are used for b → l−ν̄c. Electronic address: cnelson @ binghamton.edu