γ N → N ( 1520 ) form factors in the timelike regime

The covariant spectator quark model, tested before in a variety of electromagnetic baryon excitations, is applied here to the γ*N→N*(1520) reaction in the timelike regime. The transition form factors are first parametrized in the spacelike region in terms of a valence quark core model together with...

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Bibliographic Details
Published in:Physical review. D 2017-01, Vol.95 (1), Article 014003
Main Authors: Ramalho, G., Peña, M. T.
Format: Article
Language:English
Subjects:
Decay
Electromagnetic coupling
Form factors
Model testing
Parameterization
Pion beams
Quark models
Quarks
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Summary:The covariant spectator quark model, tested before in a variety of electromagnetic baryon excitations, is applied here to the γ*N→N*(1520) reaction in the timelike regime. The transition form factors are first parametrized in the spacelike region in terms of a valence quark core model together with a parametrization of the meson cloud contribution. The form factor behavior in the timelike region is then predicted, as well as the N*(1520)→γN decay width and the N*(1520) Dalitz decay, N*(1520)→e+e−N. Our results may help in the interpretation of dielectron production from elementary pp collisions and from the new generation of HADES results using a pion beam. In the q2=0–1  GeV2 range, we conclude that the QED approximation (a q2 independent form factor model) underestimates the electromagnetic coupling of the N*(1520) from 1 up to 2 orders of magnitude. We conclude also that the N*(1520) and Δ(1232) Dalitz decay widths are comparable.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.95.014003