{
  "id": "hep-ph/9810462",
  "version": "v2",
  "published": "1998-10-23T13:47:17.000Z",
  "updated": "1999-05-12T15:01:50.000Z",
  "title": "Angular Distribution of Decay Leptons from e^+e^- \\to W^+W^- at Threshold",
  "authors": [
    "A. Werthenbach",
    "L. M. Sehgal"
  ],
  "comment": "10 pages, 6 figures, LaTeX, simpler derivation of main results, also added a comparison with Monte Carlo expectations",
  "journal": "Phys.Lett. B458 (1999) 383-388",
  "doi": "10.1016/S0370-2693(99)00578-X",
  "categories": [
    "hep-ph"
  ],
  "abstract": "The reaction $ e^+e^- \\to W^+W^-$ produces a $W$-boson pair with a non-trivial spin correlation at threshold. This correlation leads to a characteristic angular correlation between the leptons produced in $W^{\\pm} \\to \\ell ^{\\pm} \\nu$ (angles relative to the $e^-$ beam direction): $d \\sigma /d \\cos \\theta_+ d \\cos \\theta_- \\sim (1-\\cos \\theta_+) (1+ \\cos \\theta_-) (1+\\cos \\theta_- \\cos \\theta_+) $ . If only the $\\ell^-$ is observed, its angular distribution is $d \\sigma / d \\cos \\theta_- \\sim (1+\\cos \\theta_-)(3-\\cos \\theta_-) $, implying a forward-backward asymmetry of 3/8. An analytic result is also given for the azimuthal correlation. These results are reproduced by a Monte Carlo program, that also enables us to study the effects of the $W$ decay width. The threshold behaviour, which stems from the dominance of $\\nu$-exchange, is contrasted with that due to $\\gamma$- and $Z$-exchange, which is relevant for annihilation in the helicity state $e^-_Re^+_L$.",
  "revisions": [
    {
      "version": "v2",
      "updated": "1999-05-12T15:01:50.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "angular distribution",
      "decay leptons",
      "monte carlo program",
      "characteristic angular correlation",
      "non-trivial spin correlation"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "LaTeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 478336
    }
  }
}