The eta(c)gamma gamma* transition form factor in the decay eta(c)->gamma l(+)l(-) and in the crossed channels gamma e(-)->eta(c)e(-) and e(+)e(-)->eta(c)gamma

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Di Salvo E., Rekalo M., Tomasi-Gustafsson E.

EUROPEAN PHYSICAL JOURNAL C, vol.16, no.2, pp.295-302, 2000 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 16 Issue: 2
  • Publication Date: 2000
  • Doi Number: 10.1007/s100520050022
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.295-302
  • Middle East Technical University Affiliated: No


The Dalitz distribution and the effective mass spectrum of the lepton pair produced in the decay eta(c) --> gamma l(+)l(-), as well as the differential cross sections for the crossed channels gamma e(-) --> eta(c)e(-) and e(+)e(-) --> eta(c)gamma, are calculated in terms of the sole electromagnetic transition form factor for the vertex eta(c) --> gamma gamma*, where gamma* is a virtual photon with a space-like (for gamma e(-) --> eta(c)e(-)) or a time-like (for e(+)e(-) --> eta(c)gamma and eta(c) --> gamma l(+)l(-)) four-momentum. Explicit parameterizations of the transition form factor are found in two different approaches, namely in the vector dominance model and in a QCD-inspired consideration on the basis of the process c (c) over bar --> gamma l(+)l(-), with zero relative three-momentum of the annihilating quarks.