ISSN:
1434-6052
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract. The Dalitz distribution and the effective mass spectrum of the lepton pair produced in the decay $\eta_c\to \gamma \ell^+ \ell^-$ , as well as the differential cross sections for the crossed channels $\gamma e^-\to \eta_c e^- $ and $e^+ e^-\to \eta_c \gamma$ , are calculated in terms of the sole electromagnetic transition form factor for the vertex $\eta_c\to\gamma \gamma^*$ , where $\gamma^*$ is a virtual photon with a space-like (for $\gamma e^- \to \eta_c e^- $ ) or a time-like (for $e^+ e^-\to \eta_c \gamma$ and $\eta_c\to\gamma \ell^+\ell^-$ ) 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 $c \overline c\to \gamma \ell^+ \ell^-$ , with zero relative three-momentum of the annihilating quarks.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s100520050022
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