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

R. Baldini; S. Dubnička; P. Gauzzi; S. Pacetti; E. Pasqualucci; Y. Srivastava

doi:doi:10.1007/s100529900077

2022 Impact factor 4.4

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.