{
  "id": "1108.4265",
  "version": "v1",
  "published": "2011-08-22T10:11:24.000Z",
  "updated": "2011-08-22T10:11:24.000Z",
  "title": "Dilepton production in pp and np collisions at 1.25 GeV",
  "authors": [
    "B. V. Martemyanov",
    "M. I. Krivoruchenko",
    "Amand Faessler"
  ],
  "categories": [
    "nucl-th"
  ],
  "abstract": "The inclusive reactions $pp \\rightarrow e^+ e^- X$ and $np \\rightarrow e^+ e^- X$ at the laboratory kinetic energy of 1.25 GeV are investigated in a model of dominance of nucleon and $\\Delta$ resonances. Experimental data for these reactions have recently been reported by the HADES Collaboration. In the original model, the dileptons are produced either from the decays of nucleon and $\\Delta$ resonances $R \\rightarrow N e^+ e^-$ or from the Dalitz decays of $\\pi^0$- and $\\eta$-mesons created in the $R \\to N\\pi^0$ and $R \\to N\\eta$ decays. We found that the distribution of dilepton invariant masses in the $pp \\rightarrow e^+ e^- X$ reaction is well reproduced by the contributions of $R \\rightarrow N e^+ e^-$ decays and $R \\rightarrow N \\pi^0$, $\\pi^0 \\to \\gamma e^+e^-$ decays. Among the resonances, the predominant contribution comes from the $\\Delta(1232)$, which determines both the direct decay channel $R \\rightarrow N e^+ e^-$ and the pion decay channel. In the collisions $np \\rightarrow e^+ e^- X$, additional significant contributions arise from the $\\eta$-meson Dalitz decays, produced in the $np \\rightarrow np\\eta$ and $np \\rightarrow d\\eta$ reactions, the radiative capture $np \\rightarrow d e^+ e^-$, and the $np \\rightarrow np e^+ e^-$ bremsstrahlung. These mechanisms may partly explain the strong excess of dileptons in the cross section for collisions of $np$ versus $pp$, which ranges from 7 to 100 times for the dilepton invariant masses of 0.2 to 0.5 GeV.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2011-08-22T10:11:24.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "12.40.Yx",
      "25.75.Dw",
      "13.30.Ce"
    ],
    "keywords": [
      "np collisions",
      "dilepton production",
      "dilepton invariant masses",
      "additional significant contributions arise",
      "direct decay channel"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1103/PhysRevC.84.047601",
      "journal": "Physical Review C",
      "year": 2011,
      "month": "Oct",
      "volume": 84,
      "number": 4,
      "pages": "047601"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 924621,
      "adsabs": "2011PhRvC..84d7601M"
    }
  }
}