Faddeev calculation of a K- pp quasibound state

Summary of the K−pp bound-state observation in E15 and future prospects

The possible existence of deeply-bound $\bar K$-nuclear bound states, kaonic nuclei, has been widely discussed as products of the strongly attractive $\bar K$N interaction in I = 0 channels. Investigations of those exotic states will provide us unique information of the $\bar K$N interaction below the threshold, which is still not fully understood so far. Recently, we observed the simplest kaonic nuclei, $\bar K$NN, having a much deeper binding energy than normal nuclei via inflight (K−, N) reactions at the J-PARC E15 experiment. For further studies, we have proposed a series of experimental programs for the systematic investigation of light kaonic nuclei, from $\bar K$N (Λ(1405)) to $\bar K$NNNN. We will measure the $\bar K$NNN (A = 3) system at the new experiment approved as J-PARC E80, as a first step toward a comprehensive study.

Analysis of Λ(1405) production data in the π-p → K0πΣ reaction at pπ = 1.69 GeV/c

We have been studying the (Σπ)⁰ mass distribution based on data from an old Hydrogen Bubble Chamber collected by Thomas et al. concerning the p(π^-, K⁰)Σπ reaction at p_π = 1.69 GeV/c. In this analysis we investigated the formation of the Λ(1405) state, using the Generalized Optical Theorem and T-matrix operator. We applied a combined transition operator, T_mix, which contains T₂₁ (=T_πΣ-KN) and T₂₂ (= T_πΣ-πΣ) due to the initial channel mixing in the Λ(1405) formation. We also considered a possible mixture of I = 0 and 1 in the wave function, as well as some background of the Σ(1385) population.

Studies of low-energy K- nuclear interactions by AMADEUS

The goal of the AMADEUS experiment is to shed light on unsolved fundamental issues in the non-perturbative strangeness QCD sector through the study of lowenergy K- hadronic interactions with light nuclear targets. The main open questions are the controversial nature of the Δ(1405) state, which is investigated in hyperon-pion correlation studies, and the possible existence of exotic antikaon multi-nucleon clusters, whose search in K- induced reactions is intimately related to the studies of the K- multi-nucleon absorption processes in hyperon-nucleon/nucleus channels. The DAΦNE collider at the INFN-LNF provides unique monochromatic low-momentum kaons from the φ meson decay almost at-rest, suitable for the AMADEUS studies. The KLOE detector is exploited as an active target, in order to obtain excellent acceptance and resolution data for K- nuclear capture on H, 4He, 9Be and 12C, both at-rest and in-flight.

QCD and strongly coupled gauge theories: challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.

New way to produce dense double-antikaonic dibaryon system, KKNN, through Λ(1405)-doorway sticking in p+p collisions

A recent successful observation of a dense and deeply bound K nuclear system, K-pp, in the p+p→K++K-pp reaction in a DISTO experiment indicates that the double-K dibaryon, K-K-pp, which was predicted to be a dense nuclear system, can also be formed in p+p collisions. We find theoretically that the K--K- repulsion plays no significant role in reducing the density and binding energy of K-K-pp and that, when two Λ(1405) resonances are produced simultaneously in a short-range p+p collision, they act as doorways to copious formation of K-K-pp, if and only if K-K-pp is a dense object, as predicted.

Indication of a deeply bound and compact K- pp state formed in the pp- -> pLambdaK+ reaction at 2.85 GeV

We have analyzed data of the DISTO experiment on the exclusive pp --> pLambdaK+ reaction at 2.85 GeV to search for a strongly bound compact K- pp(approximately = X) state to be formed in the pp --> K+ + X reaction. The observed spectra of the K+ missing mass and the pLambda invariant-mass with high transverse momenta of p and K+ revealed a broad distinct peak of 26-sigma confidence with a mass M(X)=2267+/-3(stat)+/-5(syst) MeV/c2 and a width Gamma(X)=118+/-8(stat)+/-10(syst) MeV. The enormously large cross section indicates formation of a compact K- pp with a large binding energy of B(K)=103 MeV, which can be a possible gateway toward cold and dense kaonic nuclear matter.

Kaonic nuclear systems KN and KNN as decaying states

The formation spectra of model KN and KNN systems formed by (K(-),n) reactions are investigated in order to obtain a theoretical basis for a proper interpretation of experimental data concerning kaonic nuclear quasi-bound states. It has been clarified that the experimentally observable kaonic nuclear state K(-)pp should be regarded as the decaying state introduced by Kapur-Peierls, which is different from the pole state solution of the Faddeev equation.

Super strong nuclear force caused by migrating K̄ mesons - Revival of the Heitler-London-Heisenberg scheme in kaonic nuclear clusters

We have studied the structure of K (-) pp comprehensively by solving this threebody system in a variational method, starting from the Ansatz that the Λ(1405) resonance (≡Λ (*)) is a K (-) p bound state. The structure of K (-) pp reveals a molecular feature, namely, the K (-) in Λ (*) as an "atomic center" plays a key role in producing strong covalent bonding with the other proton. We point out that strongly bound K̄ nuclear systems are formed by "super strong" nuclear force due to migrating real bosonic particles K̄ a la Heitler-London-Heisenberg, whereas the normal nuclear force is caused by mediating virtual mesons. We have shown that the elementary process, p + p → K (+) + Λ (*) + p, which occurs in a short impact parameter and with a large momentum transfer, leads to unusually large self-trapping of Λ (*) by the involved proton, since the Λ (*)-p system exists as a compact doorway state propagating to K (-) pp.