# The 12th International Workshop on the Physics of Excited Nucleons

10-14 June 2019
Bonn, Campus Poppelsdorf
Europe/Zurich timezone

## Is there really a narrow nucleon resonance at W=1700 MeV?

13 Jun 2019, 15:00
30m
HS 5

### HS 5

Baryon spectrum through meson photoproduction

### Speaker

Mariana Nanova (II. Physikalisches Institut, Universität Giessen)

### Description

The reaction $\gamma p \rightarrow p \pi^0 \eta$ has been studied with the Crystal Barrel/MiniTAPS detector system at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This work has been motivated by the recently claimed observation of a narrow structure around an excitation energy of 1678 MeV [1]. Invariant mass distributions and angular distributions of the final state particles have been analysed for the incident photon energy range E$_{\gamma}$ = 1400 - 1600 MeV. A structure in the M(p$\eta$) mass distribution near 1700 MeV has been indeed observed, but is found to be much broader in energy. This structure has been quantitatively studied in comparison to a partial wave analysis based on previous studies of the $\gamma p \rightarrow p \pi^0 \eta$ reaction. The observed excess yield with a cross section of abut 0.1 $\mu b$ is tentatively attributed to a so far unobserved cascade decay of the N(1900)3/2$^+$ resonance which decays via $\pi^0$ emission to the N(1710)1/2$^+$ resonance with subsequent $\eta$ decay to the nucleon ground state. This interpretation needs to be confirmed in an updated partial wave analysis.
[1] V. Kuznetsov $\textit{et al.}$, $\textit{JETP Letters}$ $\textbf{106}$ (2017) 693

### Primary author

Mariana Nanova (II. Physikalisches Institut, Universität Giessen)

### Co-author

Volker Metag (II. Physikalisches Institut, Unuversitaet Giessen)