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

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

## Partial Wave Analysis of HADES Data for Two-Pion Production in Pion-Nucleon Reactions

12 Jun 2019, 17:00
30m
HS 5

### HS 5

Partial wave analyses and baryon resonance parameter extraction

### Speaker

Izabela Ciepał (H. Niewodniczanski Institute of Nuclear Physics PAS)

### Description

The High Acceptance DiElectron Spectrometer (HADES) [1], installed at GSI Helmholtzzentrum in Darmstadt, was designed to measure emissivity of dense and hot baryonic matter. The microscopic description of the emissivity requires understanding of baryon-virtual photon couplings which can be studied in NN and $\pi$-N reactions. The elementary collisions, especially those with pion beams, also offer a great opportunity to unambiguously fix the description of baryonic resonances and their coupling to the light vector mesons rho and omega, which plays an essential role in baryon→N $\gamma$* transitions. Therefore, to understand resonances production mechanisms a systematic energy scan and high precision data are needed.
In 2014 a large dataset of $\pi$-p scattering have been obtained at the four pion beam momenta 0.656, 0.69, 0.748 and 0.8 GeV/c [2,3]. Two pion final states, $\pi^{+}\pi^{-}$ and $\pi^{-}\pi^{0}$, have been selected and investigated by the multichannel Partial Wave Analysis (PWA) developed by the Bonn-Gatchina group [4].
In this talk, total and a set of differential cross-section distributions of the two pion final states in a function of invariant masses, polar scattering, helicity and Gottfried-Jackson angles will be presented and compared to the PWA solutions. Moreover, separations of cross sections into dominant contributions like $\Delta$(1232)$\pi$,N(938)$\sigma$, N(938)$\rho$, N(1440)$1/2^{+}$ and N(1520)$3/2^{-}$ will be shown. The special attention will be paid to the role of $\rho$-N coupling.

[1] G. Agakichiev et al. (HADES Collab.), Eur. Phys. J. A 41 (2009) 243.
[2] W. Przygoda, EPJ Web of Conferences 130 (2016) 01021.
[3] I. Ciepał, W. Przygoda, EPJ Web of Conferences 199 (2019) 01024.
[4] A.V. Sarantsev, JPS Conf. Proc. 10 (2016) 010005.

### Primary authors

Izabela Ciepał (H. Niewodniczanski Institute of Nuclear Physics PAS) Witold Przygoda (Smoluchowski Institue of Physics, Jagiellonian University, Kraków, Poland) Andrey Sarantsev (HISKP)