We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction $pn\to d{\pi }^0{\pi }^0$ over the full energy region of the ABC effect, a pronounced low-mass enhancement in the $\pi \pi$-invariant mass spectrum. The measurements, which cover also the transition region to the conventional $t$-channel $\Delta \Delta$ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with $m=2.37\mathrm{GeV}$, $\Gamma \approx 70\mathrm{MeV}$ and $I(J^P)=0(3^{+})$ in both $pn$ and $\Delta \Delta$ systems. Necessary further tests of the resonance interpretation are discussed.

Exclusive and kinematically complete high-statistics measurements of quasifree polarized $\overrightarrow{n}p$ scattering have been performed in the energy region of the narrow resonancelike structure $d^{*}$ with $I(J^P)=0(3^{+})$, $M\approx 2380\mathrm{MeV}$, and $\mathrm{\Gamma }\approx 70\mathrm{MeV}$ observed recently in the double-pionic fusion channels $pn\to d{\pi }^0{\pi }^0$ and $pn\to d{\pi }^{+}{\pi }^{-}$. 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 $\overrightarrow{d}p\to np+p_{\text{spectator}}$. This allowed the $np$ analyzing power, $A_y$, to be measured over a broad angular range. The obtained $A_y$ angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new $A_y$ data into the SAID analysis produces a pole in the ${}^3{D}_3-{}^3{G}_3$ waves in support of the $d^{*}$ resonance hypothesis.

The generation of nanoalloys of immiscible metals is still a challenge using conventional methods. However, because these materials are currently attracting much attention, alternative methods are needed. In this article, we demonstrate a simple but powerful strategy for the generation of a new metastable alloy of immiscible metals. Au_1−xNi_x 3D structures with 56 at% of nickel in gold were successfully manufactured by the pulsed laser irradiation of colloidal nanoparticles. This technology can be used for preparing different metastable alloys of immiscible metals. We hypothesise that this technique leads to the formation of alloy particles through the agglomerations of nanoparticles, very fast heating and fast cooling/solidification. Thus, we expect that our approach will be applicable to a wide range of inorganic solids, yielding even new metastable solids that fail to be stable in the bulk systems and therefore do not exist in Nature.

Exclusive measurements of the quasifree $pn\to pp{\pi }^0{\pi }^{-}$ reaction have been performed by means of $pd$ collisions at $T_p$ $=$ 1.2 GeV using the wide angle shower apparatus (WASA) detector setup at the cooler synchrotron COSY (Institut für Kernphysik, Jülich). Total and differential cross sections have been obtained covering the energy region $\sqrt{s}$ $=$ (2.35–2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. No ABC effect, i.e., low-mass enhancement is found in the ${\pi }^0{\pi }^{-}$-invariant mass spectrum, in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative $s$ wave. At the upper end of the covered energy region $t$-channel processes for Roper, $\Delta \left(1600\right)$ and $\Delta \Delta$ excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at $m$ $=$ 2.37 GeV with $\Gamma$ $=$ 70 MeV and $I\left(J^P\right)=0\left(3^{+}\right)$ observed recently in $pn\to d{\pi }^0{\pi }^0$ and $pn\to d{\pi }^{+}{\pi }^{-}$ reactions leads to an agreement with the data also at low energies.