No Arabic abstract
A hypothesis is proposed herein, suggesting that a pion-nuclear resonance may be observed in the $alpha+dto{}^6mathrm{Li}(3.563)+pi^0$ reaction. The resonance has a $pi NNalpha$ structure, containing $alpha NN$ and $pi NN$ subsystems. The former corresponds to the $A=6$ isotriplet ($^6mathrm{He}_text{g.s.}$, $^6mathrm{Li}(3.563)$, $^6mathrm{Be}_text{g.s.}$), whereas the latter is a hypothetical $NN$-decoupled dibaryon. We propose an experiment to search for this resonance using the $^7mathrm{Li}(p,d)$ reaction.
The feasibility of a CLIC-LHC based FEL-nucleus collider is investigated. It is shown that the proposed scheme satisfies all requirements of an ideal photon source for the Nuclear Resonance Fluorescence method. The tunability, monochromaticity and high polarization of the FEL beam together with high statistics and huge energy of LHC nucleus beams will give an unique opportunity to determine different characteristics of excited nuclear levels. The physics potential of the proposed collider is illustrated for a beam of Pb nuclei.
The reaction p(e,e^{prime}pi^+)X^0 was studied with two high resolution magnetic spectrometers to search for narrow baryon resonances. A missing mass resolution of 2.0 MeV was achieved. A search for structures in the mass region of 0.97 < M_{X^0} < 1.06 GeV yielded no significant signal. The yield ratio of p(e,e^{prime}pi^+)X^0/p(e,e^{prime}pi^+)n was determined to be (-0.35 +/- 0.35) times 10^{-3} at 1.004 GeV and (0.34 +/- 0.42) times 10^{-3} at 1.044 GeV.
It is a well-known fact that a cluster of nucleons can be formed in the interior of an atomic nucleus, and such clusters may occupy molecular-like orbitals, showing characteristics similar to normal molecules consisting of atoms. Chemical molecules having a linear alignment are commonly seen in nature, such as carbon dioxide. A similar linear alignment of the nuclear clusters, referred to as linear-chain cluster state (LCCS), has been studied since the 1950s, however, up to now there is no clear experimental evidence demonstrating the existence of such a state. Recently, it was proposed that an excess of neutrons may offer just such a stabilizing mechanism, revitalizing interest in the nuclear LCCS, specifically with predictions for their emergence in neutron-rich carbon isotopes. Here we present the experimental observation of {alpha}-cluster states in the radioactive 14C nucleus. Using the 10Be+{alpha} resonant scattering method with a radioactive beam, we observed a series of levels which completely agree with theoretically predicted levels having an explicit linear-chain cluster configuration. We regard this as the first strong indication of the linear-chain clustered nucleus.
Recent experiments studying the meson-nucleus interaction to extract meson-nucleus potentials are reviewed. The real part of the potentials quantifies whether the interaction is attractive or repulsive while the imaginary part describes the meson absorption in nuclei. The review is focused on mesons which are sufficiently long-lived to potentially form meson-nucleus quasi-bound states. The presentation is confined to meson production off nuclei in photon-, pion-, proton-, and light-ion induced reactions and heavy-ion collisions at energies near the production threshold. Tools to extract the potential parameters are presented. In most cases, the real part of the potential is determined by comparing measured meson momentum distributions or excitation functions with collision model or transport model calculations. The imaginary part is extracted from transparency ratio measurements. Results on $K^+, K^0, K^-, eta, eta^prime, omega$, and $phi$ mesons are presented and compared with theoretical predictions. The interaction of $K^+$ and $K^0$ mesons with nuclei is found to be weakly repulsive, while the $K^-, eta,eta^prime, omega$ and $phi$ meson-nucleus potentials are attractive, however, with widely different strengths. Because of meson absorption in the nuclear medium the imaginary parts of the meson-nucleus potentials are all negative, again with a large spread. An outlook on planned experiments in the charm sector is given. In view of the determined potential parameters, the criteria and chances for experimentally observing meson-nucleus quasi-bound states are discussed. The most promising candidates appear to be the $eta$ and $eta^prime$ mesons.
Color Transparency refers to the vanishing of the hadron-nucleon interaction for hadrons produced inside a nucleus in high momentum exclusive processes. We briefly review the concept behind this unique Quantum Chromo Dynamics phenomenon, the experimental search for its onset and the recent progress made at intermediate energies.