This title appears in the Scientific Report : 2017

##### Isoscalar Single-Pion Production in the Region of Roper and $d^*(2380)$ Resonances
Personal Name(s): WASA-at-COSY Collaboration Adlarson, P. (Corresponding author) / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / IKP- Technische und Administrative Infrastruktur; IKP-TA Kernphysikalische Großgeräte; IKP-4 Zentralinstitut für Elektronik; ZEA-2 Experimentelle Hadrondynamik; IKP-2 Experimentelle Hadronstruktur; IKP-1 2017 Preprint Cosmic Matter in the Laboratory OpenAccess OpenAccess Publikationsportal JuSER
Please use the identifier: http://hdl.handle.net/2128/15005 in citations.
 Exclusive measurements of the quasi-free $pn \to pp\pi^-$ and $pp \to pp\pi^0$ reactions have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p = 0.95 - 1.3$ GeV ($\sqrt s$ = 2.3 - 2.46 GeV), which includes the regions of $\Delta(1232)$, $N^*(1440)$ and $d^*(2380)$ resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below $T_p$ = 1 GeV. We observe a substantial increase of this cross section above 1 GeV, which can be related to the Roper resonance $N^*(1440)$, the strength of which shows up isolated from the $\Delta$ resonance in the isoscalar $(N\pi)_{I=0}$ invariant-mass spectrum. No evidence for a decay of the dibaryon resonance $d^*(2380)$ into the isoscalar $(NN\pi)_{I=0}$ channel is found. An upper limit of 180 $\mu$b (90 $\%$ C.L.) corresponding to a branching ratio of 9 $\%$ has been deduced.