A new nucleon resonance in eta photoproduction

TL;DR

This paper reports the discovery of a new nucleon resonance N*(1675) in eta photoproduction, analyzing its production mechanism, spin, and parity, and suggesting it may be part of the baryon antidecuplet based on experimental and theoretical evidence.

Contribution

It introduces the N*(1675) resonance in eta photoproduction and provides a theoretical analysis of its properties and production mechanism, highlighting its possible classification within the baryon antidecuplet.

Findings

Manifest isospin asymmetry explained by transition magnetic moments.

Preference for spin-1/2 state of the resonance.

Resonance may be a non-strangeness baryon antidecuplet member.

Abstract

We present in this talk recent investigations on the nucleon-like resonance N*(1675) newly found in eta photoproduction by the GRAAL, Tohoku LNS-gamma and CB-ELSA collaborations. We focus on the production mechanism of the N*(1675), examining its spin and parity theoretically within the framework of the effective Lagrangian method. We expliucitly consider D_{13}(1520), S_{11}(1535), S_{11}(1650), D_{15}(1675), P_{11}(1710), P_{13}(1720) as well as possible background contributions. We calculate the differential cross sections and beam asymmetries for the neutron and proton targets. It turns out that there is manifest isospin asymmetry in eta photoproduction, which can be explained by the asymmetry in the transition magnetic moments: mu_{gamma p p*} =<mu_{gamma n n*}. Moreover, we find that the spin-1/2 state is preferred and this observation implies that the new resonance may be identified as a non-strangeness member of the baryon antidecuplet.