Evidence for a New Resonance from Polarized Neutron-Proton Scattering

This is the authors' abstract. We don't add key points for this paper.

Exclusive and kinematically complete high-statistics measurements of quasifree polarized →np scattering have been performed in the energy region of the narrow resonancelike structure d* with I(JP)=0(3⁺), M≈2380 MeV, and Γ≈70 MeV observed recently in the double-pionic fusion channels pn→dπ⁰π⁰ and pn→dπ⁺π^-. The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process →dp→np+pspectator. This allowed the $np$ analyzing power, Ay, to be measured over a broad angular range. The obtained Ay angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new Ay data into the SAID analysis produces a pole in the ³D₃-³G₃ waves in support of the d* resonance hypothesis.