2020 Impact factor 4.590
Particles and Fields
Eur. Phys. J. C 11, 709-715
DOI 10.1007/s100529900077

Nucleon time-like form factors below the $\mathrm{N}\overline{\mathrm{N}}$ threshold

R. Baldini1 - S. Dubnicka2 - P. Gauzzi3 - S. Pacetti1 - E. Pasqualucci3 - Y. Srivastava4

1 INFN Laboratori Nazionali di Frascati, Italy
2 Ist. of Physics, Slovak Acad. of Sciences, Bratislava, Slovakia
3 Dipartimento di Fisica dell'Università and INFN, Roma ``La Sapienza", Italy
4 Dipartimento di Fisica dell'Università and INFN, Perugia, Italy

Received: 20 January 1999 / Published online: 3 November 1999

Abstract
The nucleon magnetic form factors in the unphysical region, i.e., for time-like Q2 but below the N $\overline{\mathrm{N}}$ threshold, have been obtained by means of dispersion relations in a model-independent way, without any bias towards expected resonances. Space-like and time-like data have been employed, along with a regularization unfolding method to solve the integral equation. Remarkably, resonance structures with peaks for the $\rho (770)$ and $\rho^{\prime} (1600)$ and a structure near the $\mathrm{N} \overline{\!\mathrm{N}}$ threshold are automatically generated. The obtained $\rho$ has a much larger width, whose significance is explored. No evidence is found for a peak at the $\Phi$ mass, in spite of the expectation that such a peak exists when there is a sizeable polarized s $\overline{\mathrm{s}}$ content in the vector current of the nucleon.


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