{
  "id": "hep-ex/0508037",
  "version": "v2",
  "published": "2005-08-16T19:15:29.000Z",
  "updated": "2006-04-18T18:00:33.000Z",
  "title": "Observation of the ^1P_1 State of Charmonium",
  "authors": [
    "P. Rubin",
    "CLEO Collaboration"
  ],
  "comment": "38 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2005/, Submitted to PRD",
  "journal": "Phys.Rev.D72:092004,2005",
  "doi": "10.1103/PhysRevD.72.092004",
  "categories": [
    "hep-ex"
  ],
  "abstract": "The spin-singlet P-wave state of charmonium, hc(1P1), has been observed in the decay psi(2S) -> pi0 hc followed by hc -> gamma etac. Inclusive and exclusive analyses of the M(hc) spectrum have been performed. Two complementary inclusive analyses select either a range of energies for the photon emitted in hc -> gamma etac or a range of values of M(etac). These analyses, consistent with one another within statistics, yield M(h_c) =[3524.9 +/- 0.7 (stat) +/- 0.4 (sys)]MeV/c^2 and a product of the branching ratios B_psi(psi(2S) -> pi0 hc) x B_h(hc -> gamma etac) = [3.5 +/- 1.0 (stat) +/- 0.7 (sys)] x 10^{-4}. When the etac is reconstructed in seven exclusive decay modes, 17.5 +/- 4.5 hc events are seen with an average mass M(hc) = [3523.6 +/- 0.9 (stat) +/- 0.5 (sys)] MeV/c^2, and B_psi x B_h = [5.3 +/- 1.5 (stat) +/- 1.0 (sys)] x 10^{-4}. Because the inclusive and exclusive data samples are largely independent they are combined to yield an overall mass M(hc) = [3524.4 +/- 0.6 (stat) +/- 0.4 (sys)]MeV/c^2 and product of branching ratios B_psi x B_h = [4.0 +/- 0.8 (stat) +/- 0.7 (sys)] x 10^{-4}. The hc mass implies a P-wave hyperfine splitting Delta M_{HF}(1P) \\equiv M(1^3P)-M(1^1P_1) = [1.0 +/- 0.6 (stat) +/- 0.4 (sys)] MeV/c^2.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2006-04-18T18:00:33.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "13.20.Gd",
      "14.40.Gx",
      "13.25.Gv",
      "12.38.Qk"
    ],
    "keywords": [
      "gamma etac",
      "charmonium",
      "pi0 hc",
      "observation",
      "complementary inclusive analyses select"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "APS",
      "journal": "Phys. Rev. D"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 38,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 690020
    }
  }
}