{
  "id": "hep-ex/9904026",
  "version": "v1",
  "published": "1999-04-25T18:34:39.000Z",
  "updated": "1999-04-25T18:34:39.000Z",
  "title": "K+ -> pi+ mu+ mu- in E865 at BNL",
  "authors": [
    "Julia A. Thompson"
  ],
  "comment": "5 pages, sprocl.sty, psfig.tex, 4 embedded figures. Presented at WIN '99 in Capetown, South Africa, January 1999",
  "categories": [
    "hep-ex"
  ],
  "abstract": "Preliminary values for the K+ -> pi+ mu+ mu- branching ratio and form factor are reported, based on 400 events, a factor of 2 more in total events and 100 times the present world sample of fully reconstructed events. The results are consistent with previous results on the pi+ e+ e- mode. However, the relatively large slope of the form factor in q^2, lambda = 0.182+/-0.01+/-0.007, required to fit the pi+ e+ e- data and to give consistency between the pi+ e+ e- and pi+ mu+ mu- branching ratios, is larger than expected in simple models of the decays. The K+ -> pi+ mu+ mu- branching ratio we find, (9.23 +/- 0.6 stat +/- 0.58 syst)x10^-8, is the most precise measurement of this mode and is approximately 3.2 sigma larger than the previous measurement. These pi+ l+ l- results are inconsistent with O(p^4) Chiral Perturbation Theory but compatible with O(p^6). Systematic studies for both modes are still in progress.",
  "revisions": [
    {
      "version": "v1",
      "updated": "1999-04-25T18:34:39.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "branching ratio",
      "form factor",
      "chiral perturbation theory",
      "systematic studies",
      "preliminary values"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 498858
    }
  }
}