Publication: Observation of the Dalitz decay eta ' -> gamma e(+)e(-)
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Authors
Authors
Ablikim, M.
Achasov, M. N.
Ai, X. C.
Albayrak, O.
Albrecht, M.
Ambrose, D. J.
Amoroso, A.
An, F. F.
An, Q.
Bai, J. Z.
Advisor
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Amer Physical
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Abstract
We report the first observation of the Dalitz decay eta' -> gamma e(+)e(-), based on a data sample of 1.31 billion J/psi events collected with the BESIII detector. The eta' mesons are produced via the J/psi -> gamma eta' decay process. The ratio (eta' -> gamma e(+)e(-))/Gamma (eta' -> gamma gamma) is measured to be (2.13 +/- 0.09(stat) +/- 0.07(sys)) x 10(-2). This corresponds to a branching fraction B(eta' -> gamma e(+)e(-)) = (4.69 +/- 0.20(stat) +/- 0.23(sys)) x 10(-4). The transition form factor is extracted and different expressions are compared to the measured dependence on the e(+)e(-) invariant mass. The results are consistent with the prediction of the vector meson dominance model.
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Keywords
Form-factors, Dominance, Pi-0, Astronomy & astrophysics, Physics