${\gamma }^{\ast }N\to N^{\ast }(1520)$ form factors in the timelike regime

Abstract

The covariant spectator quark model, tested before in a variety of electromagnetic baryon excitations, is applied here to the ${\gamma }^{\ast }N\to N^{\ast }(1520)$ 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 $N^{\ast }(1520)\to \gamma N$ decay width and the $N^{\ast }(1520)$ Dalitz decay, $N^{\ast }(1520)\to e^{+}{e}^{-}N$. 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 $q^2=0$--1 GeV${}^2$ range we conclude that the {\it QED approximation} (a $q^2$ independent form factor model) underestimates the electromagnetic coupling of the $N^{\ast }(1520)$ from 1 up to 2 orders of magnitude. We conclude also that the $N^{\ast }(1520)$ and the $\Delta (1232)$ Dalitz decay widths are comparable.

Published version. 12 pages, 10 figures

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Cited by in corpus (15)

• Electromagnetic Transition Form Factors of Baryon Resonances
• Pion and Kaon box contribution to $a_{\mu }^{\text{HLbL}}$
• Dilepton Radiation from Strongly Interacting Systems
• Semirelativistic approximation to the ${\gamma }^{\ast }N\to N(1520)$ and ${\gamma }^{\ast }N\to N(1535)$ transition form factors
• Pentaquark components in low-lying baryon resonances
• Electromagnetic form factors of the ${\Omega }^{-}$ baryon in the spacelike and timelike regions
• Covariant model for the Dalitz decay of the $N(1535)$ resonance
• A covariant model for the decuplet to octet Dalitz decays
• Role of baryon resonances in the ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ reaction within an effective-Lagrangian model
• Weak interaction axial form factors of the octet baryons in nuclear medium
• Meson cloud contributions to the Dalitz decays of decuplet to octet baryons
• Dilepton Decay of Low-mass $\rho$ Mesons
• Electroweak form factors of baryons in dense nuclear matter
• Helicity amplitudes of $N(1520)$ and $N(1535)$ including pentaquark components
• About the magnitude of the ${\gamma }^{\ast }N\to N(1520)$ transverse amplitudes near $Q^2=0$