Diphoton and dipion productions at the Nuclotron/NICA

Along with $ \pi^{0}$ and $ \eta$ mesons, a resonance structure in the invariant-mass spectrum of two photons at $ M_{\gamma\gamma} = 360 \pm 7 \pm 9$ MeV is observed in the reaction $ d C \rightarrow \gamma + \gamma +X$ at momentum 2.75GeV/c per nucleon. Estimates of its width and production cross section are $ \Gamma = 64 \pm 18$ MeV and $ \sigma_{\gamma\gamma} = 98 \pm 24^{+93}_{-67}$ μb, respectively. The collected statistics amount to $ 2339 \pm 340$ events of $ 1.5\cdot 10^{6}$ triggered interactions of a total number $ \sim 10^{12}$ of $ d+C$ interactions. This resonance structure is not observed in the $ \gamma$ $ \gamma$ channel in $ \sim 10^{11} p+ C$ collisions at the beam momentum 5.5GeV/c . The result obtained in the reaction $ d+ C$ is confirmed by the second experiment carried out on the deuteron beam at momentum 3.83GeV/c per nucleon with a copper target: $ M = 382 \pm 13$ MeV, $ \Gamma = 62 \pm 37$ MeV and $ \sigma = 273 \pm 75$ μb. Some results on the observation of the resonance in the invariant-mass spectra of two $ \pi^{0}$ mesons are presented: the data obtained in the $ d+C\rightarrow \gamma+\gamma + X$ reaction is confirmed by the results for the $ d+C\rightarrow \pi^{0} +\pi^{0} + X$ and $ p+C\rightarrow \pi^{0} +\pi^{0} + X$ reactions; a preliminary estimate of the ratio $ Br(R\rightarrow\gamma\gamma)/Br (R\rightarrow\pi^{0}\pi^{0})$ is $ (1.8-3.7)\cdot 10^{-3}$ . Further studies of this resonance is assumed at the Nuclotron/NICA at higher setup acceptance, which will allow to elucidate the nature of this resonance by determination of the differential cross sections at different beam energies in the range 1-6GeV/n and the mechanism of its formation.