Mesic Nuclei Research Articles

Formation of $\eta '(958)$ Bound States by $(\gamma ,d)$ Reaction

We have investigated the 6Li(gamma, d) reaction theoretically for the formation of the eta'(958) mesic nucleus. We have reported the numerical results in this article.

Heavy Hadrons in Dense Matter

We study the behavior of dynamically-generated baryon resonances with heavy- quark content within a unitarized coupled-channel theory in matter that fulfills heavy-quark spin symmetry constraints. We analyze the implications for the formation of charmed mesic nuclei and the propagation of heavy mesons in heavy-ion collisions from RHIC to FAIR.

Eta-mesic nuclei: Past, present, future

Eta-mesic nucleus or the quasibound nuclear state of an eta (η) meson in a nucleus is caused by strong interaction force alone. This new type of nuclear species, which extends the landscape of nuclear physics, has been extensively studied since its prediction in 1986. In this paper, we review and analyze in great detail the models of the fundamental η–nucleon interaction leading to the formation of an η–mesic nucleus, the methods used in calculating the properties of a bound η, and the approaches employed in the interpretation of the pertinent experimental data. In view of the successful observation of the η–mesic nucleus 25 Mg η and other promising experimental results, future direction in searching for more η–mesic nuclei is suggested.

Unresolved Issues in the Search for Eta-mesic Nuclei

Even if the theoretical definition of an unstable state is straightforward, its experimental identification often depends on the method used in the analysis and extraction of data. A good example is the case of eta mesic nuclei where strong hints of their existence led to about three decades of extensive theoretical and experimental searches. Considering the still undecided status of these states and the limitations in the understanding of the eta-nucleon as well as the eta-nucleus interaction, the present article tries to look back at some unresolved problems in the production mechanism and final state interaction of the eta mesons and nuclei. An unconventional perspective which provides a physical insight into the nature of the eta-nucleus interaction is also presented using quantum time concepts.

Search for mesic nuclei in the photoproduction of ηπ0 mesons off light nuclei

For the understanding of the strong nuclear force, the study of interaction between mesons and nuclei is important. In case of long lived charged mesons, like π and K, secondary beams can be used for experiments. But the situation is different for the short lived neutral mesons, like π0, η and η'. The only access is indirect, making use of final-state interaction (FSI). The mesons are produced with some initial reaction in the nucleus and then their interaction with the same nucleus is studied. It is much discussed whether it is possible to form, via the strong interaction, quasi-bound states of mesons and nuclei, which would be the ideal tool for such studies. We will present preliminary results from the Crystal Ball/TAPS experiment at the Mainz MAMI accelerator for double neutral meson photoproduction, showing interesting potential to study meson nucleon interaction and discuss their relevance. The very first attempt has been made to measure the quasi-free behavior of the photoproduction of ηπ0 mesons from the 2H.

Meson properties from mesic atoms and mesic nuclei

Meson properties are believed to have close connection to the fundamental theory, QCD, and have been studied for a long time both theoretically and experimentally. In this report, we study the recent activities in this field and consider the η (958) mesic nuclei and the deeply bound pionic atoms. We summarize the possible formation of the η (958) mesic nuclei by the ( p, d ) reactions and report the new possibilities of the spectroscopic study of the pionic atoms using the ( d , 3 He) reactions.

Search for the4He-ηbound state indd→ (4He-η)bound→3Henπ0anddd→ (4He-η)bound→3Hepπ−reactions with the WASA-at-COSY facility

In November 2010, the search for the 4He-{\eta} bound state was per formed with high statistics and high acceptance with the WASA-at-COSY facility using a ramped beam technique. The signature of eta - mesic nuclei is searched for in the measured excitation functions for the two reaction channels: dd ->3He n pi0 and dd ->3He p pi- near the eta production threshold. This report includes the description of the experimental method and the status of the data analysis.

Eta Meson Production in Proton-Deuteron Collisions

Since many years the strong final state interaction between η -mesons and light nuclei and the discussed possibility for the formation of η -mesic nuclei has attracted broad experimental and theoretical investigations. Prominent examples are production experiments on the 3 He-η final state which present an unexpected strong total cross section enhancement at threshold, indicating the presence of a pole very close to threshold. Stimulated by these results new proton-deuteron collision experiments on the η meson production have been performed in the near-threshold region and at higher excess energies using both polarized and unpolarized beams. Recent results are presented and discussed in this contribution.

QCD Symmetries in $\eta $- and $\eta '$-Mesic Nuclei

We discuss the role of QCD symmetries and confinement in understanding eta and etaprime mesic nuclei. Eta and etaprime bound states in nuclei are sensitive to the flavour-singlet component in the meson. The bigger the singlet component, the more attraction and the greater the binding. Recent results on the etaprime mass in nuclei from the CBELSA/TAPS collaboration are very similar to the prediction of the Quark Meson Coupling model. In the model eta-etaprime mixing induces a factor of two enhancement of the eta-nucleon scattering length relative to the prediction with a pure octet eta, with real part about 0.8 fm.

Missing Mass Spectroscopy ofη′ Mesic Nuclei with the (p,d) Reaction at GSI

We plan a missing-mass spectroscopy experiment of 0 mesic nuclei with the 12 C(p,d) 0 11 C reaction to study in-medium properties of the 0 meson. In nuclear medium, due to restoration of chiral symmetry, the mass of the 0 meson may be reduced, and 0 bound states in a nucleus may exist. The experiment will be started at GSI with a 2.5 GeV proton beam using FRS as a spectrometer and will be continued at Super-FRS at FAIR. The plan of the experiment and development of a Cherenkov detector and an optics mode are described.

Meson Properties at Finite Density from Mesic Atoms and Mesic Nuclei

Meson Properties at Finite Density from Mesic Atoms and Mesic Nuclei

Formation ofη′(958)-mesic nuclei by the (p,d) reaction

We calculate theoretically the formation spectra of eta'(958)-nucleus systems in the (p,d) reaction for the investigation of the in-medium modification of the eta' mass. We show the comprehensive numerical calculations based on a simple form of the eta' optical potential in nuclei with various potential depths. We conclude that one finds an evidence of possible attractive interaction between eta' and nucleus as peak structure appearing around the eta' threshold in light nuclei such as 11C when the attractive potential is stronger than 100 MeV and the absorption width is of order of 40 MeV or less. Spectroscopy of the (p,d) reaction is expected to be performed experimentally at existing facilities, such as GSI. We also estimate the contributions from the omega and phi mesons, which have masses close to the eta' meson, concluding that the observation of the peak structure of the eta'-mesic nuclei is not disturbed although their contributions may not be small.

Formation of the η′(958)-mesic nuclei in missing mass spectroscopies

Abstract We calculate the formation cross section of the η ′ -mesic nuclei by ( π , N ) and ( p , d ) reactions based on the latest theoretical considerations of the η ′ properties in nucleus. The results shown here are important to give predictions and support for future experiments and to establish the connection between the η ′ mesic nucleus formation spectra and the modifications of the η ′ properties at finite density, which will give us new information on the η ′ mass generation mechanism.

Spectroscopy of η′ Mesic Nuclei with (p, d) Reaction

We are going to perform an inclusive spectroscopy experiment of eta' mesic nuclei with the 12C(p,d) reaction to study in-medium properties of the eta' meson. In nuclear medium, the eta' meson mass may be reduced due to partial restoration of chiral symmetry. In case of sufficiently large mass reduction and small absorption width of eta' at normal nuclear density, peak structures of eta' mesic states in 11C will be observed near the eta' emission threshold even in an inclusive spectrum. The experiment will be carried out at GSI with proton beam supplied by SIS using FRS as a spectrometer. The detail of the experiment is described.

Formation of η′(958) Meson Bound States and Chiral Symmetry In-Medium

We theoretically discuss the feasibility to observe the η′(958)-mesic nuclei by using the missing mass spectroscopy. We evaluate the η′-nucleus optical potential including the contribution of lowest order in density together with the second order terms account for η′ absorption by two nucleons, based on a recent model of the η′N interaction. We show the calculated formation cross section of the η′ bound states from (π, N) reaction with pion beam momentum pπ = 1.8 GeV/c and (p, d) reaction with proton kinetic energy Tp = 2.5 GeV.

Strangeness and charm in nuclear matter

The properties of strange ($K$, $\bar K$ and $\bar K^*$) and open-charm ($D$, $\bar D$ and $D^*$) mesons in dense matter are studied using a unitary approach in coupled channels for meson-baryon scattering. In the strangeness sector, the interaction with nucleons always comes through vector-meson exchange, which is evaluated by chiral and hidden gauge Lagrangians. For the interaction of charmed mesons with nucleons we extend the SU(3) Weinberg-Tomozawa Lagrangian to incorporate spin-flavor symmetry and implement a suitable flavor symmetry breaking. The in-medium solution for the scattering amplitude accounts for Pauli blocking effects and meson self-energies. On one hand, we obtain the $K$, $\bar K$ and $\bar K^*$ spectral functions in the nuclear medium and study their behaviour at finite density, temperature and momentum. We also make an estimate of the transparency ratio of the $\gamma A \to K^+ K^{*-} A^\prime$ reaction, which we propose as a tool to detect in-medium modifications of the $\bar K^*$ meson. On the other hand, in the charm sector, several resonances with negative parity are generated dynamically by the s-wave interaction between pseudoscalar and vector meson multiplets with $1/2^+$ and $3/2^+$ baryons. The properties of these states in matter are analyzed and their influence on the open-charm meson spectral functions is studied. We finally discuss the possible formation of $D$-mesic nuclei at FAIR energies.

Search for Eta-mesic Helium via Deuteron–Deuteron Reactions with the WASA-at-COSY Facility

The -mesic nuclei in which the meson is bound with nucleus via strong interaction was postulated already in 1986, however till now no experiment conrmed empirically its existence. The discovery of this new kind of an exotic nuclear matter would be very important for better understanding of the meson structure and its interaction with nucleons. The search for -mesic helium is carried out with high statistic and high acceptance with the WASA-at-COSY detection setup in the Forschungszentrum

Feasibility Study of Observing ' Mesic Nuclei with (p,d) Reaction

A novel method is proposed to measure eta'(958) meson bound states in 11C nuclei by missing mass spectroscopy of the 12C(p,d) reaction near the eta' production threshold. It is shown that peak structures will be observed experimentally in an inclusive measurement in case that the in-medium eta' mass reduction is sufficiently large and that the decay width of eta' mesic states is narrow enough. Such a measurement will be feasible with the intense proton beam supplied by the SIS synchrotron at GSI combined with the good energy resolution of the fragment separator FRS.

Search for mesic nuclei at J-PARC

Experimental programs at J-PARC with regards to K̄ and η-nuclear systems are reviewed in this article. Both of them are theoretically expected to exist as bound states, based on the attractive nature of the meson-nucleon interaction. In-medium properties of pseudoscalar mesons may be investigated by looking into these bound states.

Total and Differential Cross Sections of the Reaction pd →3He +ηat 49 and 60 MeV Excess Energy

The p + d → 3 He + η reaction has been used recently for various precision experiments at COSY-Julich, e.g. for the investigation of the η -nucleus final state interaction, the search for possible η -mesic nuclei as well as for the η -mass determination with highest accuracy. A remarkable feature of this reaction is the unexpected shape of the excitation function which is strongly influenced by the η -3 He final state interaction. While close to threshold (Q ≤ 11MeV) a rich data sample has been provided by the ANKE collaboration, only limited information are available at higher excess energies. Therefore, new measurements at Q = 49 and 60MeV with high statistics have been performed at the WASA-at-COSY experiment. Due to the large angular acceptance of the detector detailed investigations on angular distributions as well as their energy dependance have been performed and will be presented and discussed.Supported by COSY-FFE grants