Search

We present a reaction model to describe the fast removal of the $\alpha$-particle core in $^8$He nucleus with eventual emission of four neutrons. The obtained four neutron energy distributions allows to explain the sharp low energy peak observed by studying the missing mass spectra of four neutrons in [Nature Vol. 606, p. 678], as a consequence of dineutron-dineutron correlations., Comment: Accepted to PRL

The fundamental question is how the hyperon plays a role in the nuclear structure. It is of particular importance, especially in the light mass region, to verify the structure change when $\Lambda$ particle(s) is added to normal nuclei. The ground state of $^{8}$Be has been know to have a well-developed $\alpha$--$\alpha$ cluster structure, whereasn$^{12}$C has a mixed structure of three $\alpha$ clusters and $jj$-coupling shell model, where $\alpha$ clusters are partially broken. Adding $\Lambda$ particle(s) could induce the structure change. We compare the Be and C cases. Using the antisymmetrized quasi-cluster model (AQCM), the $\alpha$-cluster states and $jj$-coupling shell-model states of $^8$Be and $^{12}$C are prepared on the same footing, and we add $\Lambda$ particles. The cluster-shell competition in the ground state can be well described with this model. Using AQCM, we calculate $^8$Be, $^{9}_{\Lambda}$Be, $^{10}_{\Lambda\Lambda}$Be, $^{12}$C, $^{13}_{\Lambda}$C, and $^{14}_{\Lambda\Lambda}$C. By adding one or two $\Lambda$ particle(s), the ground state of $^{12}$C approaches the $jj$-coupling shell model side. On the other hand, in the Be case, although the $\Lambda$ particle(s) shrinks the $\alpha$--$\alpha$ distance, the breaking effect of the cluster structure is rather limited. The spin-orbit interaction is the driving force of breaking the $\alpha$ clusters, and whether the glue-like effect of $\Lambda$ particle(s) attracts the cluster inside the range of this interaction is crucial. In $^{14}_{\Lambda\Lambda}$C, the breaking of $\alpha$ clusters in $^{12}$C is much enhanced by the addition of the $\Lambda$ particles than the case of free $^{12}$C. We also found that breaking $\alpha$ clusters in the ground state of $^{14}_{\Lambda\Lambda}$C affects the excited state with the pure cluster structure.

We study the single- and double-Λ hypernuclei in Zr isotopes with the Hartree–Fock–Bogoliubov model and Skyrme-type nucleon–nucleon, Λ–nucleon, and Λ–Λ interactions. We found two peculiar features of the Λ hyperon halo phenomena that have never been found in nuclei without the strangeness degree of freedom. One is the d-wave halo, and the other is a bunch of three halo orbits just below the Λ hyperon threshold in $^{137}_\Lambda$Zr and also in $^{138}_{\Lambda \Lambda }$Zr. We name these exotic halo phenomena giant hyperon halos in hypernuclei whose core nucleus 136Zr was predicted to have a “giant neutron halo.” The interaction between Λ hyperons and the neutrons is responsible for inducing giant hyperon halo phenomena in the single- and double-Λ nuclei $^{137}_\Lambda$Zr and $^{138}_{\Lambda \Lambda }$Zr.

We have investigated the possible existence of a $^7$H resonant state, considered as a five-body system consisting of a $^3$H core with four valence neutrons. To this aim, an effective n-$^3$H potential is constructed in order to reproduce the low energy elastic neutron scattering on $^3$H phase shifts and the $^5$H resonant ground state in terms of $^3$H-n-n system. The variational Gaussian Expansion Method is used to solve the 5-body Schr\"{o}dinger equation, while the resonant state parameters were estimated by means of the stabilization method. We have not found any sign of a narrow low energy resonance in the vicinity of $^3$H+4n threshold. However, we have identified a very broad structure at $E_R\approx 9$ MeV above this threshold, which corresponds to the $^7$H J$^{\pi}$=1/2$^+$ ground state. In the vicinity of this state, we have also identified a broad structure corresponding to the ground state of $^6$H isotope with quantum numbers $J^{\pi}=2^-$., Comment: 15 pages, 9 figures

Spectrum of the doubly heavy tetraquarks, bbq¯q¯, is studied in a constituent quark model. Four-body problem is solved in a variational method where the real scaling technique is used to identify resonant states above the fall-apart decay thresholds. In addition to the two bound states that were reported in the previous study we have found several narrow resonant states above the BB⁎ and B⁎B⁎ thresholds. Their structures are studied and are interpreted by the quark dynamics. A narrow resonance with spin-parity JP=1+ is found to be a mixed state of a compact tetraquark and a B⁎B⁎ scattering state. This is driven by a strong color Coulombic attraction between the bb quarks. Negative-parity excited resonances with JP=0−, 1− and 2− form a triplet under the heavy-quark spin symmetry. It turns out that they share a similar structure to the λ-mode of a singly heavy baryon as a result of the strongly attractive correlation for the doubly heavy diquark.

We overview our recent calculations of scattering cross sections of positronium–antihydrogen collisions. We discuss the cross sections calculated in the vicinity of the four-body resonances of $$\bar{\mathrm {H}}\mathrm {Ps}$$ and above the energy threshold for the formation of the antihydrogen positive ions ( $$\bar{\mathrm {H}}^+$$ ). In the former energy region where a Rydberg series of resonances dominated by the $$\bar{\mathrm {H}}^+$$ - $$\hbox {e}^-$$ interaction appears, we show a good agreement between the resonant profiles in the cross sections and the resonance energies calculated by the complex coordinate rotation method. $$\bar{\mathrm {H}}^+$$ production cross sections near the threshold energy are reported for the positronium being initially in the (n, l) states with $$n\le 3$$ , together with all competing elastic/inelastic cross sections. Comparison of our results with the latest continuum distorted wave final state calculation is presented. A qualitative discrepancy concerning the dependence of cross sections on the angular momentum of Ps is indicated.

We present four-body calculations of double-heavy tetraquarks in quark model. Several bound states are found for various flavor combinations. One of them is a strongly bound $$bb {\bar{q}} {\bar{q}}$$ with isospin and spin-parity $$I(J^P) = 0(1^+)$$ , having a binding energy of almost 200 MeV. This is consistent with the predictions of lattice QCD. We have also found a shallow state for the same $$I(J^P) = 0(1^+)$$ channel. By computing density distributions, it is shown that the deep one is a compact tetraquark state, while the shallow one is regarded as a loosely-bound molecule of two color singlet mesons, B and $$B^*$$ . This is a hadronic analogue of the cluster formation in light nuclei, the first example that hadrons with totally different nature emerge from a single Hamiltonian.

Investigations of double- $$\Lambda $$ hypernuclei, which contain two $$\Lambda $$ hyperons in a nucleus, provide valuable information on baryon–baryon interaction in the strangeness $$-2$$ sector, such as the $$\Lambda $$ – $$\Lambda $$ interaction. Whereas several double- $$\Lambda $$ hypernuclei have been discovered in nuclear-emulsion experiments, an experimental observation of $${}_{\Lambda \Lambda }^{5}$$ H is awaited. It is not only because $$_{\Lambda \Lambda }^{5}$$ H is theoretically expected to be the lightest bound state, but also because $$\Lambda \Lambda $$ – $$\Xi N$$ coupling may play an important role in its structure. On the other hand, the coupling effect may be suppressed in $$_{\Lambda \Lambda }^{6}{\mathrm {He}}$$ .We propose an experiment to investigate $$_{\Lambda \Lambda }^{5}$$ H at J-PARC. $$_{\Lambda \Lambda }^{5}$$ H will be produced by a decay of a $$\Xi $$ hypernucleus, $$_\Xi ^{7}$$ H, which can be produced by the $$^7\mathrm {Li}(K^-,K^+)$$ reaction. The mass of $$_{\Lambda \Lambda }^{5}$$ H will be determined by means of decay pion spectroscopy; it can be calculated from the measured momentum of decay pions, owing to a two-body decay of $$_{\Lambda \Lambda }^{5}$$ H.

The Weinberg operator (chromo-electric dipole moment of gluon) is a CP violating quantity generated in many candidates of new physics beyond the standard model, and it contributes to observables such as the electric dipole moments (EDM) of the neutron or atoms which are currently measured in experiments. In this proceedings contribution, we report on our result of the evaluation of the Weinberg operator contribution to the nucleon EDM in the nonrelativistic quark model using the Gaussian expansion method., Comment: 6 pages, 3 figures, proceedings of the 8th Asia-Pacific conference on Few-Body problems in Physics (APFB2020), Kanazawa, Japan, March 2021

We evaluate the contribution of the CP violating gluon chromo-electric dipole moment (the so-called Weinberg operator, denoted as $w$) to the electric dipole moment (EDM) of nucleons in the nonrelativistic quark model. The CP-odd interquark potential is modeled by the perturbative one-loop level gluon exchange generated by the Weinberg operator with massive quarks and gluons. The nucleon EDM is obtained by solving the nonrelativistic Schr\"{o}dinger equation of the three-quark system using the Gaussian expansion method. It is found that the resulting nucleon EDM, which may reasonably be considered as the irreducible contribution, is smaller than the one obtained after $\gamma_5$-rotating the anomalous magnetic moment using the CP-odd mass calculated with QCD sum rules. We estimate the total contribution to be $d_n = w \times 20 \, e \, {\rm MeV}$ and $d_p = - w \times 18 \, e \, {\rm MeV}$ with 60% of theoretical uncertainty., Comment: 13 pages, 6 figures

We investigate the properties of $\Lambda$ hyperon in $\Lambda$-hypernuclei using an effective nuclear density functional theory which is based on the low-energy effective field theory. It expands the energy density in the power of Fermi momentum, and consequently has multiple density dependence for the effective many-body interactions. Starting from the effective density functional for nucleons, we determine the parameters for the two- and many-body $\Lambda$-$N$ interactions added to the nucleon energy density functional by fitting to $\Lambda$-hypernuclear data. The experimental data consist of the energy levels of a $\Lambda$ hyperon in the $p$-, and $d$-states as well as $s$-state of $\Lambda$-hypernuclei in the mass range from $_\Lambda^{16}$O to $_\Lambda^{208}$Pb. The results turn out to properly explain the data relevant to hypernuclei owing to the effective many-body interaction apart from a few data in light hypernuclei. This hyperon functional is applied to study the $\Lambda$ hyperon binding energy of the neutron-rich $^{124-136}_\Lambda$Sn isotopes which are under consideration for the measurement at J-PARC. Our results are shown to be insensitive to the density dependence of symmetry energy. We also examine the nuclear matter including $\Lambda$ hyperon. We note that the hyperon threshold density depends on the nuclear matter properties., Comment: 22 pages, 3 tables, 8 figures

We study the structure of $_{\mathrm{\ensuremath{\Lambda}}}^{9}\mathrm{Be}$ within the framework of the three-body $\ensuremath{\alpha}+\ensuremath{\alpha}+\mathrm{\ensuremath{\Lambda}}$ cluster model using the YNG-NF interaction with the Gaussian expansion method. We obtain the energies of bound states as well as energies and decay widths of the resonant states with the complex scaling method. By analyzing our wave functions of bound states and resonant states, we confirm three analog states of $_{\mathrm{\ensuremath{\Lambda}}}^{9}\mathrm{Be}$ pointed out by Band\ifmmode \bar{o}\else \={o}\fi{} and Motoba et al. [T. Motoba, H. Band\ifmmode \bar{o}\else \={o}\fi{}, and K. Ikeda, Prog. Theor. Phys. 70, 189 (1983); T. Motoba, H. Band\ifmmode \bar{o}\else \={o}\fi{}, K. Ikeda, and T. Yamada, Prog. Theor. Phys. Suppl. 81, 42 (1985); H. Band\ifmmode \bar{o}\else \={o}\fi{}, K. Ikeda, and T. Motoba, Prog. Theor. Phys. 69, 918 (1983)], $^{8}\mathrm{Be}$ analog states, $_{\mathrm{\ensuremath{\Lambda}}}^{9}\mathrm{Be}$ genuine states, and $^{9}\mathrm{Be}$ analog states. The new states of $_{\mathrm{\ensuremath{\Lambda}}}^{9}\mathrm{Be}$ are also obtained at a high energy region with broader decay widths.

Bound states of double-heavy tetraquarks are studied in a constituent quark model. Two bound states are found for isospin and spin-parity I(JP)=0(1+) in the bbu¯d¯ channel. One is deeply bound and compact made of colored diquarks, while the other is shallow and extended as a BB⁎ molecule. The former agrees well with lattice QCD results. A systematic decrease in the binding energy is seen by replacing one of the heavy quarks to a lighter one. Altogether we find ten bound states. It is shown for the first time that hadrons with totally different natures emerge from a single Hamiltonian.

Both unitary chiral theories and lattice QCD simulations show that the DK interaction is attractive and can form a bound state, namely, $$D^*_{s0}(2317)$$ D s 0 ∗ ( 2317 ) . Assuming the validity of the heavy antiquark–diquark symmetry, the $$\Xi _{cc}{\bar{K}}$$ Ξ cc K ¯ interaction is the same as the DK interaction, which implies the existence of a $$\Xi _{cc}{\bar{K}}$$ Ξ cc K ¯ bound state with a binding energy of $$49-64$$ 49 - 64 MeV. In this work, we study whether a $$\Xi _{cc}\Xi _{cc}{\bar{K}}$$ Ξ cc Ξ cc K ¯ three-body system binds. The $$\Xi _{cc}\Xi _{cc}$$ Ξ cc Ξ cc interaction is described by exchanging $$\pi $$ π , $$\sigma $$ σ , $$\rho $$ ρ , and $$\omega $$ ω mesons, with the corresponding couplings related to those of the NN interaction via the quark model. We indeed find a $$\Xi _{cc}\Xi _{cc}{\bar{K}}$$ Ξ cc Ξ cc K ¯ bound state, with quantum numbers $$J^P=0^-$$ J P = 0 - , $$I=\frac{1}{2}$$ I = 1 2 , $$S=1$$ S = 1 and $$C=4$$ C = 4 , and a binding energy of 80–118 MeV. With the same formalism, we find that the $$\Xi _{cc}\bar{\Xi }_{cc}{\bar{K}}$$ Ξ cc Ξ ¯ cc K ¯ system also binds, yielding a $$I(J^P)=\frac{1}{2}(0^+)$$ I ( J P ) = 1 2 ( 0 + ) state and a $$\frac{1}{2}(1^+)$$ 1 2 ( 1 + ) state with binding energies of 56–68 MeV and 56–67 MeV respectively. As a byproduct, we show the existence of a $$NN{\bar{K}}$$ N N K ¯ state with a binding energy of 35–43 MeV, consistent with the results of other theoretical works and experimental data, which serves as a consistency check on the predicted $$\Xi _{cc}\Xi _{cc}{\bar{K}}$$ Ξ cc Ξ cc K ¯ bound state.

The mass spectra of singly charmed and bottom baryons, $\Lambda_{c/b}(1/2^\pm,3/2^-)$ and $\Xi_{c/b}(1/2^\pm,3/2^-)$, are investigated using a nonrelativistic potential model with a heavy quark and a light diquark. The masses of the scalar and pseudoscalar diquarks are taken from a chiral effective theory. The effect of $U_A(1)$ anomaly induces an inverse hierarchy between the masses of strange and non-strange pseudoscalar diquarks, which leads to a similar inverse mass ordering in $\rho$-mode excitations of singly heavy baryons., Comment: 10 pages, 2 figures, 3 tables; published version

We review recent progress in S=−2 hypernuclei such as double-Λ hypernuclei and Ξ hypernuclei, which are composed of a nucleus and one or two hyperons, such as a Λ or a Ξ particle. Through observations of [Formula: see text]He, such as the Nagara event, we obtain important information about the ΛΛ interaction. Using this information, we perform a four-body calculation of ααΛΛ for [Formula: see text]Be, which was observed at KEK as the Demachi–Yanagi event. We interpret this event as the [Formula: see text] excited state. We calculate energy levels of [Formula: see text]Be within the framework of an αα nΛΛ five-body cluster model, and then interpret the Hida event, which was observed at KEK as the ground state of [Formula: see text]Be. Motivated by observation of the Kiso event of [Formula: see text]C, by using the Skyrme–Hartree–Fock and relativistic mean-field frameworks, we calculate the energy spectra of this hypernucleus. We interpret this event as the 14N(g.s.)+Ξ−(0 p) state. Finally, we propose an experiment on [Formula: see text]H and [Formula: see text]Li to extract information about the spin- and isospin-averaged parts of the Ξ N interaction.

The J-PARC Hadron Experimental Facility was constructed with an aim to explore the origin and evolution of matter in the universe through experiments with intense particle beams. In the past decade, many results from particle and nuclear physics experiments have been obtained at the present facility. To expand the physics programs to as yet unexplored regions, the extension project of the Hadron Experimental Facility has been extensively discussed. This contribution presents the physics of the extension of the Hadron Experimental Facility to resolve issues related to strangeness nuclear physics, hadron physics, and flavor physics.

We investigate structure of C Λ 13 and discuss the difference and similarity between the structures of C 12 and C Λ 13 by answering the questions if the linear-chain and gaslike cluster states, which are proposed to appear in C 12 , survives, or new structure states appear or not. We introduce a microscopic cluster model called, Hyper-Tohsaki–Horiuchi–Schuck–Ropke (H-THSR) wave function, which is an extended version of the THSR wave function so as to describe Λ hypernuclei. We obtained two bound states and two resonance (quasi-bound) states for J π = 0 + in C Λ 13 , corresponding to the four 0 + states in C 12 . However, the inversion of level ordering between the spectra of C 12 and C Λ 13 , i.e. that the 0 3 + and 0 4 + states in C Λ 13 correspond to the 0 4 + and 0 3 + states in C 12 , respectively, is shown to occur. The additional Λ particle reduces sizes of the 0 2 + and 0 3 + states in C Λ 13 very much, but the shrinkage of the 0 4 + state is only a half of the other states, in spite of the fact that attractive Λ-N interaction makes nucleus contracted so much when the Λ particle occupies an S-orbit. In conclusion, the Hoyle state becomes quite a compact object with Be Λ 9 + α configuration in C Λ 13 and is no more gaslike state composed of the 3α clusters. Instead, the 0 4 + state in C Λ 13 , coming from the C 12 ( 0 3 + ) state, appears as a gaslike state composed of α + α + Λ 5 He configuration, i.e. the Hoyle analog state. A linear-chain state in a Λ hypernucleus is for the first time predicted to exist as the 0 3 + state in C Λ 13 with more shrunk arrangement of the 3α clusters along z-axis than the 3α linear-chain configuration realized in the C 12 ( 0 4 + ) state. All the excited states are shown to appear around the corresponding cluster-decay threshold, reflecting the threshold rule.

Experimental evidence exists that the Ξ-nucleus interaction is attractive. We search for NNΞ and NNNΞ bound systems on the basis of the AV8 NN potential combined with either a phenomenological Nijmegen ΞN potential or a first principles HAL QCD ΞN potential. The binding energies of the three-body and four-body systems (below the d+Ξ and ^{3}H/^{3}He+Ξ thresholds, respectively) are calculated by a high precision variational approach, the Gaussian expansion method. Although the two ΞN potentials have significantly different isospin (T) and spin (S) dependence, the NNNΞ system with quantum numbers (T=0, J^{π}=1^{+}) appears to be bound (one deep for Nijmegen and one shallow for HAL QCD) below the ^{3}H/^{3}He+Ξ threshold. Experimental implications for such a state are discussed.

We consider the evolution of the neutron-nucleus scattering length for the lightest nuclei. We show that, when increasing the number of neutrons in the target nucleus, the strong Pauli repulsion is weakened and the balance with the attractive nucleon-nucleon interaction results into a resonant virtual state in $^{18}$B. We describe $^{19}$B in terms of a $^{17}$B-$n$-$n$ three-body system where the two-body subsystems $^{17}$B-$n$ and $n$-$n$ are unbound (virtual) states close to the unitary limit. The energy of $^{19}$B ground state is well reproduced and two low-lying resonances are predicted. Their eventual link with the Efimov physics is discussed. This model can be extended to describe the recently discovered resonant states in $^{20,21}$B., Proceedings for the 24th edition of European Few Body Conference, Surrey, UK, 2-4 September 2019

We study the hypernuclei of C and B isotopes by Hartree-Fock model with Skyrme-type nucleon-nucleon and nucleon-hyperon interactions. The calculated $\Lambda$ binding energies agree well with the available experiment data. We found halo structure in the hyperon $1p$-state with extended wave function beyond nuclear surface in the light C and B isotopes. We also found the enhanced electric dipole transition between $1p$- and $1s$-hyperon states, which could be the evidence for this hyperon halo structure., Comment: 16 pages, 2 figures, 3 tables

Double-Λ hypernuclei provide invaluable information on Λ–Λ interaction, as a scattering experiment with a hyperon target is impossible. For more than half a century, double-Λ hypernuclei have been searched for by using nuclear emulsion. We will propose a novel counter experiment (J-PARC P75 experiment), aiming at investigating a light double-Λ hypernucleus, \(_{\Lambda \Lambda }^{\ \ \ 5}\text{H}\). The ΛΛ binding energy will be determined by decay pion spectroscopy. The experimental method of production and identification of \(_{\Lambda \Lambda }^{\ \ \ 5}\text{H}\) is discussed.

The $DK$ interaction is strong enough to form a bound state, the ${D}_{s0}^{*}(2317)$. This in turn begs the question of whether there are bound states composed of several charmed mesons and a kaon. Previous calculations indicate that the three-body $DDK$ system is probably bound, where the quantum numbers are ${J}^{P}={0}^{\ensuremath{-}}$, $I=\frac{1}{2}$, $S=1$ and $C=2$. The minimum quark content of this state is $cc\overline{q}\overline{s}$ with $q=u$, $d$, which means that, if discovered, it will be an explicitly exotic tetraquark. In the present work. we apply the Gaussian expansion method to study the $DDDK$ system and show that it binds as well. The existence of these three and four body states is rather robust with respect to the $DD$ interaction and subleading (chiral) corrections to the $DK$ interaction. If these states exist, it is quite likely that their heavy quark symmetry counterparts exist as well. These three-body $DDK$ and four-body $DDDK$ molecular states could be viewed as counterparts of atomic nuclei, which are clusters of nucleons bound by the residual strong force, or chemical molecules, which are clusters of atoms bound by the residual electromagnetic interaction.

We present a model description of the bound $^{19}\mathrm{B}$ isotope in terms of a $^{17}\mathrm{B}\ensuremath{-}n\ensuremath{-}n$ three-body system where the two-body subsystems $^{17}\mathrm{B}\ensuremath{-}n$ and $n\ensuremath{-}n$ are unbound (virtual) states close to the unitary limit. The $^{19}\mathrm{B}$ ground state is well described in terms of two-body potentials only, and two low-lying resonances are predicted. Their eventual link with the Efimov physics is discussed. This model can be naturally used to describe the recently discovered resonant states in $^{20,21}\mathrm{B}$.

We calculate the contribution of the $|\mathrm{\ensuremath{\Delta}}S|=1\phantom{\rule{4pt}{0ex}}K$ meson exchange process generated by the Cabibbo--Kobayashi--Maskawa matrix to the electric-dipole moment (EDM) of the $^{9}\mathrm{Be}$ nucleus by considering the $\ensuremath{\alpha}n\text{\ensuremath{-}}\ensuremath{\alpha}\mathrm{\ensuremath{\Lambda}}$ channel coupling. It is found that the effect of the Pauli exclusion principle is not important intermediate $S=\ensuremath{-}1$ state, and that the result is consistent with the EDM of $^{9}\mathrm{Be}$ calculated with the $|\mathrm{\ensuremath{\Delta}}S|=1$ interactions as a perturbation without considering the nucleus-hypernucleus mixing. Our result suggests that the effect of the $|\mathrm{\ensuremath{\Delta}}S|=1$ interactions is neither suppressed nor enhanced in nuclei, if the difference of binding energies between the nucleus and the hypernucleus is small compared with the hyperon-nucleon mass difference.

In the framework of $$\alpha +\alpha +\varLambda $$ three-body cluster model, we calculate energy spectra from bound energy region to resonant energy region up to around 20 MeV with respect to $$\alpha \alpha \varLambda $$ threshold. To calculate resonant states, we employ Complex Scaling method which is one of the powerful method. We obtain the states of $$^8$$ Be analogue and genuine hypernuclear analogue, which are consistent with those by Yamada et al. (Prog Theor Phys Suppl 81:104, 1985). However, the calculated ordering of $$^9$$ Be analogue states is quite different with their calculation. We also obtain $$2^+$$ and $$4^+$$ resonant states of which have been never pointed out.

We describe 19B in terms of a 17B-n-n three-body system, where the two-body subsystems 17B-n and n-n are unbound (virtual) states close to the unitary limit. The energy of 19B ground state is well reproduced and two low-lying resonances are predicted. Their eventual link with the Efimov physics is discussed. This model can be extended to describe the recently discovered resonant states in 20,21B., 27th International Nuclear Physics Conference (INPC2019). arXiv admin note: substantial text overlap with arXiv:1912.05427

The universal properties of charged particles are modified by the presence of a long-range Coulomb interaction. We investigate the modification of Efimov universality as a function of the Coulomb strength using the Gaussian expansion method. The resonant short-range interaction is described by Gaussian potentials to which a Coulomb potential is added. We calculate binding energies and root mean square radii for the three- and four-body systems of charged particles and present our results in a generalised Efimov plot. We find that universal features can still be discerned for weak Coulomb interaction, but break down for strong Coulomb interaction. The root-mean-square radius plateaus at increasingly smaller values for strong Coulomb interaction and the probablity distributions of the states become more concentrated inside the Coulomb barrier. As an example, we apply our universal model to nuclei with an alpha-cluster substructure. Our results point to strong non-universal contributions in that sector., 18 pages, 9 figures, final version (with small orthographical corrections)

We outline the concept of a proposed experiment (P75) at J-PARC, whose aim is to investigate the double-Λ hypernucleus HΛΛ5 by using the 7Li(K−, K+) reactions. In particular, the production of HΛΛ5 via the decay of HΞ−7 and decay pion spectroscopy of HΛΛ5 after removing a background from the single-Λ hypernucleus HΛ4 are highlighted.

By solving the 5-body Faddeev-Yakubovsky equations in configuration space with realistic nuclear Hamiltonians we have studied the resonant states of $^5$H isotope. Two different methods, allowing to bypass the exponentially diverging boundary conditions, have been employed providing consistent results. The existence of $^5$H broad J$^{\pi}$=1/2$^+$,3/2$^+$,5/2$^+$ states as S-matrix poles has been confirmed and compared with the, also calculated, resonant states in $^4$H isotope. We have established that the positions of these resonances only mildly depend on the nuclear interaction model., Comment: to appear in Physics Letters B (2019)

We have developed a coupled-rearrangement-channel method allowing the rigorous non-adiabatic treatment of the multi-channel scattering problem for four particles. We present the study of the binding, resonant and collisional properties of the (H) over bar -Ps system with the total angular momentum J = 0(+) (singlet positronic configuration). The binding energy, the life-times of the resonant states and the collisional cross sections are calculated and discussed. We present the preliminary cross sections for the elastic and inelastic (H) over bar -Ps scattering, notably for the excitation of Ps and for the rearrangement reaction producing the (H) over bar (+) ions.

The instanton effects on the charmonium spectrum is discussed in the framework of nonrelativistic potential model. The results from constituent quark model without inclusion of instanton effects is compared with the results for `the potential from constituent quark model + the contribution from the instanton liquid model'. We consider two models with the corresponding instanton potentials and discuss their relevance to explanations of the origin phenomenological parameters used in the nonrelativistic potential models. We also present the universal instanton potential in the parametrized form which can be useful in practical calculations., 8 pages, 1 figure

We review our calculation method, Gaussian expansion method (GEM), and its applications to various few-body (3- to 5-body) systems such as 1) few-nucleon systems, 2) few-body structure of hypernuclei, 3) clustering structure of light nuclei and unstable nuclei, 4) exotic atoms/molecules, 5) cold atoms, 6) nuclear astrophysics and 7) structure of exotic hadrons. Showing examples in our published papers, we explain i) high accuracy of GEM calculations and its reason, ii) wide applicability of GEM and iii) successful predictions by GEM calculations before measurements. GEM was proposed 30 years ago and has been applied to a variety of subjects. To solve few-body Schroedinger equations accurately, use is made of the Rayleigh-Ritz variational method for bound states, the complex-scaling method for resonant states and the Kohn-type variational principle to S-matrix for scattering states. The total wave function is expanded in terms of few-body Gaussian basis functions spanned over all the sets of rearrangement Jacobi coordinates. Gaussians with ranges in geometric progression work very well both for short-range and long-range behavior of the few-body wave functions. Use of Gaussians with complex ranges gives much more accurate solution when the wave function has many oscillations., 30 pages, 46 figures, an invited review paper for the international symposium in honor of Prof. Akito Arima for his 88th birthday, to be published in Frontiers of Physics, Vol.13 (2018)