{
  "id": "hep-ph/9901425",
  "version": "v1",
  "published": "1999-01-26T21:24:42.000Z",
  "updated": "1999-01-26T21:24:42.000Z",
  "title": "Nucleon matrix elements of twist-3 and 4 operators from the instanton vacuum",
  "authors": [
    "J. Balla",
    "M. V. Polyakov",
    "C. Weiss"
  ],
  "comment": "6 pages, LaTeX. Oral contribution to the 8th International Conference on the Structure of Baryons (Baryons '98), Bonn, Sep. 22-26, 1998; to appear in the Proceedings",
  "categories": [
    "hep-ph"
  ],
  "abstract": "The spin-dependent twist-3 and 4 nucleon matrix elements d^(2) and f^(2) describing power corrections to the Bjorken and Ellis-Jaffe sum rules are computed in the instanton vacuum. A systematic expansion in the small packing fraction of the instanton medium, rho / R << 1, is performed. We find that the twist-3 matrix element d^(2) is suppressed [of order (rho / R)^4], while the twist-4 matrix element f^(2) is of order unity. Numerically, d^(2) << f^(2). The small value of d^(2) \\sim 10^{-3} obtained from instantons is consistent with the recent E143 measurements of the structure function g_2, where d^(2) enters at the same level as the twist-2 contribution.",
  "revisions": [
    {
      "version": "v1",
      "updated": "1999-01-26T21:24:42.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nucleon matrix elements",
      "instanton vacuum",
      "ellis-jaffe sum rules",
      "small value",
      "order unity"
    ],
    "tags": [
      "conference paper"
    ],
    "note": {
      "typesetting": "LaTeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 482514,
      "adsabs": "1999hep.ph....1425B"
    }
  }
}