Search

A recent paper Ohkubo (2017) [1] found that the measured S 0 1 phase shifts can be reproduced using a deeply attractive nucleon–nucleon potential. We find that the deuteron would decay strongly via pion emission to the deeply bound state arising in this potential. Therefore the success of a deeply attractive potential in describing phase shifts must be regarded only as an interesting curiosity.

In the framework of the energy density method with the use of the wave function of the two-center shell model, the influence of the simultaneous account for the Pauli exclusion principle and the monopole and quadrupole polarizations of nuclei on the nuclear part of the potential of their interaction by the example of the Ca 40 + Ca 40 system is considered. The calculations performed in the framework of the adiabatic approximation show that the consideration of the Pauli exclusion principle and the polarization of nuclei, especially the quadrupole one, essentially affects the nucleus–nucleus interaction potential.

The dissipation phenomenon in the heavy-ion reaction at incident energy near Fermi energy is studied by simulating the reactions 129Xe + 129Sn and 58Ni + 58Ni with isospin-dependent quantum molecular dynamics model (IQMD). The isotropy ratio in terms of transverse and longitudinal energies of the free protons emitted in the final states of these reactions is quantitatively analyzed to explore the in-medium correlation of the binary collisions. Comparison of the calculations with the experimental data recently released by INDRA collaboration exhibits that the ratio is very sensitive to the Pauli blocking effect in two-body collisions and Pauli exclusion principle is indispensable in the theoretical simulations for the heavy-ion reactions near the Fermi energy.

We construct new equations of state for baryons at sub-nuclear densities for the use in core-collapse supernova simulations. The abundance of various nuclei is obtained together with thermodynamic quantities. The formulation is an extension of the previous model, in which we adopted the relativistic mean field theory with the TM1 parameter set for nucleons, the quantum approach for $d$, $t$, $h$ and $\alpha$ as well as the liquid drop model for the other nuclei under the nuclear statistical equilibrium. We reformulate the model of the light nuclei other than $d$, $t$, $h$ and $\alpha$ based on the quasi-particle description. Furthermore, we modify the model so that the temperature dependences of surface and shell energies of heavy nuclei could be taken into account. The pasta phases for heavy nuclei and the Pauli- and self-energy shifts for $d$, $t$, $h$ and $\alpha$ are taken into account in the same way as in the previous model. We find that nuclear composition is considerably affected by the modifications in this work, whereas thermodynamical quantities are not changed much. In particular, the washout of shell effect has a great impact on the mass distribution above $T \sim 1$ MeV. This improvement may have an important effect on the rates of electron captures and coherent neutrino scatterings on nuclei in supernova cores., Comment: 39 pages, 6 figures, 2 tables, Accepted for publication in Nucl.Phys. A. This article draws heavily from arXiv:1305.1508. The EOS table available at http://sites.google.com/site/furusawashun/eosdata

In this paper, the variation of the nuclear matter properties during the fusion reaction and also its relationship with the hindrance phenomenon are examined in the 64Ni+64Ni reaction. For this purpose, the inter-nuclear potential is calculated by using the Skyrme energy density functional formalism in which the used forces are in a wide range of the incompressibility values. The obtained results indicate that by increasing bombarding energy the nuclear matter incompressibility is increasing. Also, this variation shows that nuclear matter exhibits a very soft behavior when moving from the sub-barrier to the deep sub-barrier region in this reaction, which can cause a large overlapping between the interacting nuclei. Since the repulsion arising from the Pauli exclusion principle affects this large overlapping, so it can lead to the fusion hindrance and the fall-off of the cross-sections in the 64Ni+64Ni reaction.

We discuss Dirac and Pauli form factors based on a generalized parton distribution framework in the range of high momentum transfers of t 30 GeV 2 and calculate the electromagnetic form factors, G E and G M , for the proton. In previous work, Gaussian parameterization has been used in wave functions for calculating electromagnetic form factors at intermediate-high momentum transfers of 1 GeV 2 t 10 GeV 2 ; in this paper, by considering an improved Gaussian ansatz, we not only calculate the electromagnetic form factors at moderately high momentum transfers t but also can calculate these quantities at high momentum transfers, achieving reasonable agreement with experimental data and other previous work.

We argue that the large instanton induced Pauli form factor in polarized proton-proton scattering may cause, through topological fluctuations, substantial charge-dependent azimuthal correlations for pi^+/pi^- production in peripheral heavy ion collisions both at RHIC and LHC, thanks to the large induced magnetic field. Our results compare favorably to the measured pion azimuthal correlations by the STAR and ALICE collaborations., Comment: 4 pages, 5 figures, Latex

In scattering theory the effect associated with the downward crossing of the phase-shift δ l ( k ) ( l being the orbital angular momentum and k the momentum) through δ l = π / 2 (mod π ) is called echo . In the standard nuclear theory (Breit–Wigner theory) the echo is described and evaluated in terms of scattering by an impenetrable sphere. However, this model holds only at sufficiently high energy, while it is inadequate at low energy. In this paper we show that the echo effect can be associated with two different regimes acting at low and high energy, respectively. At high energy the hard-sphere scattering model seems to describe appropriately the phenomenon. At low energy we propose a mechanism due to the exchange forces induced by the Pauli exclusion principle in the fermionic interaction, which leads to nonlocal potentials. These potentials admit for the scattering amplitude pole singularities in the fourth quadrant of the complex angular momentum plane. This paper analyzes the role played by this class of poles in the description of the low energy regime of echoes. A specific phenomenological analysis is performed, taking as typical example the α – α elastic scattering.

The in-medium ηN interaction near and below threshold is constructed from a free-space chirally-inspired meson–baryon coupled-channel model that captures the physics of the N ⁎ ( 1535 ) baryon resonance. Nucleon Pauli blocking and hadron self-energies are accounted for. The resulting energy-dependent in-medium interaction is used in self-consistent dynamical calculations of η nuclear bound states. Narrow states of width Γ η ≲ 2 MeV are found across the periodic table, beginning with A ⩾ 10 , for this in-medium coupled-channel interaction model. The binding energy of the 1 s η state increases with A, reaching a value of B 1 s ( η ) ≈ 15 MeV . The implications of our self-consistency procedure are discussed with respect to procedures used in other works.

A three-body calculation for the He Λ 6 and H Λ 6 hypernuclei, in which the respective cores are He 4 and H Λ 4 , has been initiated. The interactions in the He Λ 6 system are reasonably well known. For example, the Λn interaction is approximately determined by bubble-chamber Λ–p scattering data, the He 4 –Λ interaction can be fitted to the He Λ 5 binding energy, and the He 4 –n interaction can be fitted to α–n scattering data. For He 4 –n the s-wave can be modeled alternatively as a repulsive potential (Eskandarian and Afnan, 1992 [1] ) or as an attractive potential with a forbidden bound state (Lehman, 1982 [2] ). We examine the effect of these alternatives on He 6 and Li 6 , because the interaction comes into play in modeling He Λ 6 as well as in our H Λ 4 + n + n model of H Λ 6 , where the valence neutrons are Pauli blocked from the s-shell of the core.

Origin of the short-range baryon–baryon interactions is discussed from the quark substructure viewpoints of baryons. It is pointed out that the generalized nuclear force, recently obtained from the lattice QCD calculations, can be interpreted at short distances by the combinatory effects of the Pauli exclusion principle and the color–magnetic spin–spin interactions among the quarks. Classifications according to the spin-flavor SU(6) symmetry representations give us a general guidance on the features of the short-range interactions. The SU(6) analysis of the three-body baryon interactions reveals that the genuine three-body force is repulsive at short distances due to the quark antisymmetrization.

We investigate the 6He dipole distribution in a three-body α+n+n model. Two approaches are used to describe the three-body 1− continuum: the discretized-continuum method, where the scattering wave functions are approximated by square-integrable functions, and the R-matrix formalism, where their asymptotic behaviour is taken into account. We show that some ambiguity exists in the pseudostate method, owing to the smoothing technique, necessary to derive continuous distributions. We show evidence for the important role of the halo structure in the E1 dipole strength. We also address the treatment of Pauli forbidden states in the three-body wave functions.

A simple model, in which nuclei are represented as homogeneous spheres of symmetric nuclear matter, is used to study the effects of a self-consistent pairing interaction on the isoscalar nuclear response. Effects due to the finite size of nuclei are suitably taken into account. The semiclassical equations of motion derived in a previous paper for the time-dependent Hartree–Fock–Bogoliubov problem are solved in an improved (linear) approximation in which the pairing field is allowed to oscillate and to become complex. The new solutions are in good agreement with the old ones and also with the result of well-known quantum approaches. The role of the Pauli principle in eliminating one possible set of solutions is also discussed. The density response function is explicitly evaluated and it is shown that the energy-weighted sum rule is restored to its correct value by a part of the fluctuations of the imaginary pairing field. The remaining part of these imaginary fluctuations, together with the fluctuations of the real part, could give rise to collective excitations in the density response function. A detailed analysis of the monopole and quadrupole strength functions shows that there are practically no collective effects in these channels at low excitation energy.

Recent theoretical studies predicted that, due to nuclear correlations across the N=40 shell gap, electron captures on nuclei with proton numbers Z 40 would not be strongly suppressed due to Pauli blocking of Gamow–Teller (GT) transitions. This prediction has recently been confirmed by the experimental determination of the single-particle occupation numbers in 76Se and by the measurement of the 76Se GT+ strength distribution. In this manuscript we derive such occupation numbers and GT+ distributions within large-scale shell model studies. Based on the same models, we calculate stellar electron capture rates and compare them to those obtained from the experimental GT+ data.

Recently, Dolgov and Smirnov speculated that neutrinos may not obey the principle named after their inventor, the Pauli Principle. The neutrino wave function may contain a bosonic component. In principle, two-neutrino double-beta (2ν2β) decay data could be used to check on the conjecture that neutrinos violate the Pauli Principle. Recent 2ν2β data on 100Mo to both the ground state and excited states in 100Ru will be used to illustrate the procedure.

The contribution of Pauli exchange terms to the two--nucleon induced non--mesonic weak decay of $^{12}_\Lambda$C hypernuclei, $\Lambda NN\to nNN$ ($N=n$ or $p$), is studied within a nuclear matter formalism implemented in a local density approximation. We have adopted a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. The introduction of exchange terms turns out to reduce the two--nucleon induced non--mesonic rate by 18% and, jointly with an increase in the one--nucleon induced rate by the same magnitude, reveals to be significant for an accurate determination of the full set of hypernuclear non--mesonic decay widths in theoretical and experimental analyses., Comment: 14 pages, 3 figures

Within the microscopic model based on the algebraic version of the resonating group method the role of the Pauli principle in the formation of continuum wave function of nuclear systems composed of three identical $s$-clusters has been investigated. Emphasis is placed upon the study of the exchange effects contained in the genuine three-cluster norm kernel. Three-fermion, three-boson, three-dineutron ($3d'$) and $3\alpha$ systems are considered in detail. Simple analytical method of constructing the norm kernel for $3\alpha$ system is suggested. The Pauli-allowed basis functions for the $3\alpha$ and $3d'$ systems are given in an explicit form and asymptotic behavior of these functions is established. Complete classification of the eigenfunctions and the eigenvalues of the $^{12}$C norm kernel by the $^8$Be$=\alpha+\alpha$ eigenvalues has been given for the first time. Spectrum of the $^{12}$C norm kernel is compared to that of the $^{5}$H system., Comment: 22 pages, 2 tables, submitted to Nuclear Physics A

New approach to the problem of multichannel continuum spectrum of three-cluster systems composed of an s-cluster and two neutrons is suggested based on the discrete representation of a complete basis of allowed states of the multiparticle harmonic oscillator. The structure of the eigenfunctions and behavior of the eigenvalues of the three-cluster norm kernel are analyzed. Classification of the eigenvalues of the three-cluster systems with the help of eigenvalues of the two-body subsystem is suggested. Asymptotic boundary conditions for a three-cluster wave function in the continuum consistent with the requirements of the Pauli principle are established. Such asymptotic behavior corresponds rather to subsequent decay of the three-cluster system than to the so-called "democratic decay" associated with the hyperspherical harmonics. The 3H+n+n configuration of the 5H nucleus is considered in detail., Comment: 18 pages, 3 figures, 3 tables

Recent developments are summarised concerning low-energy K ¯ N interactions as they relate to the possible existence of antikaon-nuclear quasibound states. An exploratory study of antikaons bound to finite nuclei is performed, with emphasis on the evolution of such states from light to heavy nuclei (A = 16–208). The energy dependent, driving attractive K ¯ N interactions are constructed using the s -wave coupled-channel amplitudes involving the Λ ( 1405 ) and resulting from chiral SU ( 3 ) dynamics, plus p -wave amplitudes dominated by the Σ ( 1385 ) . Effects of Pauli and short-range correlations are discussed. The decay width induced by K − N N two-body absorption is estimated and found to be substantial. It is concluded that K ¯ -nuclear quasibound states can possibly exist with binding energies ranging from 60 to 100 MeV, but with short life times corresponding to decay widths of similar magnitudes.

Single and double coincidence nucleon spectra in the $\Lambda$-hypernuclei weak decay are evaluated and discussed using a microscopic formalism. Nuclear matter is employed together with the local density approximation which allows us to analyze the $^{12}_{\Lambda}C$ hypernucleus non-mesonic weak decay. Final state interactions (FSI) are included via the first order (in the nuclear residual interaction) terms to the RPA, where the strong residual interaction is modelled by a Bonn potential. At this level of approximation, these FSI are pure quantum interference terms between the primary decay $(\Lambda N \to NN)$ and $(\Lambda N \to NN \to NN)$, where the strong interaction is responsible for the last piece in the second reaction. Also the Pauli exchange contributions are explicitly evaluated. We show that the inclusion of Pauli exchange terms is important. A comparison with data is made. We conclude that the limitations in phase space in the RPA makes this approximation inadequate to reproduce the nucleon spectra. This fact, does not allow us to draw a definite conclusion about the importance of the interference terms., Comment: 39 pages, 10 figures

Sturmian theory for nucleon-nucleus scattering is discussed in the presence of all the phenomenological ingredients necessary for the description of weakly-bound (or particle-unstable) light nuclear systems. Currently, we use a macroscopic potential model of collective nature. The analysis shows that the couplings to low-energy collective-core excitations are fundamental but they are physically meaningful only if the constraints introduced by the Pauli principle are taken into account. The formalism leads one to discuss a new concept, Pauli hindrance, which appears to be important to understand the structure of weakly-bound and unbound systems.

Our previously developed two-frequency folded-diagram method is applied to calculate the binding energy of 5ΛHe starting with Nijmegen YN potentials NSC89 and NSC97(a-f). Since the masses of a hyeron and a nucleon are different and so may be their binding energies in a hypernucleus, wave functions of a hyperon and a nucleon are treated with different frequencies. The frequency ℏ ω N for a nucleon in 5ΛHe is set constant according to an empirical formula, while that for a hyperon ℏ ω Y remains as a parameter. The G-matrix elements are calculated exactly by using an exact Pauli exclusion operator. We then obtain the Λ's single particle energy in 5ΛHe as a function of ℏ ω Λ . A stable ℏ ω Λ can be found at the saturate minimum. Results from various modes of the realistic Nijmegen NSC89 and NSC97 YN potentials are compared to each other. Calculations by switching ℏ ω N to other values are also done. The result from NSC97f is found to be closest to the experimental value. Possible implications of the results are discussed.

The charged current one pion production induced by ν μ in 12C has been studied. The calculations have been done for the incoherent and the coherent pion production processes assuming Δ dominance and take into account the effects of the Pauli blocking, Fermi motion, renormalization of the Δ properties in a nuclear medium and the final state interaction effects of pions with the residual nucleus. The numerical results have been compared with the preliminary experimental results of the MiniBooNE collaboration in 12C.

Experimental differential cross sections for elastic scattering of two α particles have been fitted with an l -independent non-monotonic real potential up to 34.2 MeV (lab) and a complex potential with non-monotonic real part from 35.1 to 47.3 MeV (lab). The calculated phase shifts, in general, agree with those derived from the phase shift analyses of the experimental cross sections. In particular, the s- and d-wave phase shifts tend to zero in the limit of zero energy implying the absence of any bound state. Thus, 8 Be is unbound in the potential and the calculated decay width of about 6 eV agrees with the observed one. This potential has its roots in the energy-density functional (EDF) theory with the sudden approximation. In fact, the calculated angular distributions using the derived EDF potential are in reasonable agreement with the experimental data at some energies up to 15.2 MeV (lab). Modifying the Buck, Friedrich and Wheatley (BFW) potential by adding a small repulsive core leads to about the same quality of fits. The modified BFW potential, however, binds 8 Be in Pauli forbidden states, and s- and d-wave phase shifts in it tend to 2 π and π , respectively, in the limit of zero energy.

We perform semi-classical molecular dynamics simulations of screening by bound electrons in low energy nuclear reactions. In our simulations quantum effects corresponding to the Pauli and Heisenberg principle are enforced by constraints. In addition to the well known adiabatic and sudden limits, we propose a new "dissipative limit" which is expected to be important not only at high energies but in the extremely low energy region. The dissipative limit is associated with the chaotic behavior of the electronic motion. It affects also the magnitude of the enhancement factor. We discuss also numerical experiments using polarized targets. The derived enhancement factors in our simulation are in agreement with those extracted within the $R$-matrix approach., Comment: 17 pages, 9 figures

Elastic scattering angular distributions for systems with reduced mass between 3 and 34 and energies varying between 25 and 120 MeV/nucleon were analyzed. The stable $^4$He, its exotic partner $^6$He, and the weakly bound $^{6,7}$Li nuclei were included as projectiles in the systematics. Optical model data analyzes were performed with an adjustable factor of normalization included in the imaginary part of the potential. These analyzes indicated a reduction of absorption for systems with small reduced masses that was detected due to the refractive nature of the scattering by light systems., Comment: 16 pages, 7 figures

The possibility of α -cluster condensation in 12 C is examined. A fully microscopic 12-nucleon, 3 α -cluster model is applied for the ground state and the 0 + state near the 3 α -particle threshold. The wave functions for these states are obtained in a correlated Gaussian basis by the stochastic variational method and then mapped to 3 α -boson wave functions through an α -spectroscopic amplitude. Characteristics of the boson structure are discussed by calculating several relevant quantities. The consequence of the Pauli principle on the bosonic properties is discussed. The extent of α -condensation is quantified by diagonalizing the density matrices constructed from the boson wave functions. The probability that the α -clusters occupy a single S -orbit is about 70% for the 0 + state at the excitation energy of 7.65 MeV.

Energies, electromagnetic moments and transitions in light, nuclei are calculat,ed in t,he microscopic dynamic-correlation model (DCM) which is based on large correhted basis of Slateris determinants charact,erized by an increasing numbcr of core excited states. Microscopic calculations are performed for the magnetic moments and transit,ions of iBe and I3C. The magnetic moments of 6Li, 7Li, and iLi are also calculated. Further, rcsult,s obt,ained for matt,er and charge ra.dii of 7B~ and iBe arc reported. The overall results obt#ained for these light odd- and even-nuclei show that, t,he correct treatment of the Pauli principle and the diagonalizat,ion of large dimensional spaces are not compat,ible with the simple picture generatled by cluster models.

The recent quark-model baryon-baryon interaction by the Kyoto-Niigata group is applied to the three-nucleon, 2αΓ and 2Γα systems, in which a new three-cluster Faddeev formalism, using the 2-cluster resonating-group method (RGM) kernel, is developed for the exact treatment of the Pauli forbidden states between clusters.

Pauli-Blocking effect on the kinetic term is investigated by employing the quark cluster model. The effect can be understood by the change of the degrees of the mixing between the incoming wave and the 0$\ell$ state of the inter-cluster wave function, which can be expressed by a potential which is highly nonlocal. We look into the properties of this effect by comparing equivalent local potentials. In the channel where the Pauli-blocking effect is small, the on-shell equivalent local potential simulates the nonlocal potential well even for the off-shell behavior. On the other hand, the off-shell behavior is very different from the original one where the effect is large. This off-shell behavior, however, can well be simulated by considering the nonlocal matrix elements only between the $0s$ state and the other states. The energy dependent potentials are also constructed and found to be helpful to understand the energy dependence of the effect.

The suppression and enhancement effects of ΛΛ - ζN coupling are investigated in s -shell double-Λ hypernuclei. The Pauli suppression due to this coupling in ΛΛ 6 He is found to be be 0.43 MeV for the coupling strength of the NSC97e potential. This indicates that the free-space ΛΛ interaction is stronger by about 5° phase shift than that deduced from the empirical data of ΛΛ 6 He without including the Pauli suppression effect. In ΛΛ 5 He and ΛΛ 5 H, an attractive term arising from ΛΛ - ζN conversion is enhanced by the formation of an alpha particle in intermediate ζ states. According to this enhancement, ΔB ΛΛ of ΛΛ 5 He is about 0.27 MeV larger than that of ΛΛ 6 He.

The 1$^-$ excitations of the three--body halo nucleus $^{11}$Li are investigated. We use adiabatic hyperspherical expansion and solve the Faddeev equations in coordinate space. The method of complex scaling is used to compute the resonance states. The Pauli forbidden states occupied by core neutrons are excluded by constructing corresponding complex scaled phase equivalent two-body potentials. We use a recently derived neutron--core interaction consistent with known structure and reaction properties of $^{10}$Li and $^{11}$Li. The computed dipole excited states with $J^\pi=1/2^+$, $J^\pi=3/2^+$, and $J^\pi=5/2^+$ have energies ranging from 0.6 MeV to 1.0 MeV and widths between 0.15 MeV and 0.65 MeV. We investigate the dependence of the complex energies of these states on the $^{10}$Li spectrum. The finite spin 3/2 of the core and the resulting core-neutron spin-spin interaction are important. The connection with Coulomb dissociation experiments is discussed and a need for better measurements is pointed out., Comment: 28 pages, 6 figures, Nuclear Physics A, in press

We use the induced interaction of Babu and Brown to derive two novel relations between the quasiparticle interaction in nuclear matter and the unique low momentum nucleon-nucleon interaction V_low k in vacuum. These relations provide two independent constraints on the Fermi liquid parameters of nuclear matter. We derive the full renormalization group equations in the particle-hole channels from the induced interaction. The new constraints, together with the Pauli principle sum rules, define four combinations of Fermi liquid parameters that are invariant under the renormalization group flow. Using empirical values for the spin-independent Fermi liquid parameters, we are able to compute the major spin-dependent ones by imposing the new constraints and the Pauli principle sum rules. The effects of tensor forces are discussed., 30 pages, 4 figures, uses feynmp.sty (included), minor revisions, to appear in Nucl. Phys. A

We calculate proton elastic scattering with 58 Ni and 120 Sn at various intermediate energies with relativistic impulse approximation (RIA). We use the ground-state wave functions of the relativistic mean-field (RMF) calculation with the use of the TMA parameter set. We found good agreement with experimental data for the elastic scattering observables. In addition to the standard scalar and vector densities, we include also the tensor density. We study the Pauli effect and the vacuum polarization effect on the elastic scattering observables using the prescription of Horowitz and Serot at lower energy.

The Landau parameters have been calculated in relativistic nonlinear models, on the one hand from the second derivative of the total energy density with respect to the quasinucleon distribution, on the other from the longitudinal dielectric function in relativistic RPA with and without the Pauli blocking terms in the polarization operators. The links between the Landau parameters and the collective modes obtained in the space-like region have been discussed.

Weak decay of hypernuclei, first cousin to the {beta}-decay of conventional, nonstrange nuclei, was initially observed in the 1950s. Pionic decay rates have proven a challenge--to reconcile nuclear decay rates with that of free {lambda} decay. Pauli blocking of the decay nucleon plays an important role. Nonmesonic decay provides our only practical means of exploring the four-fermion, strangeness-changing N{Lambda} {yields} NN weak interaction. The N{Lambda}{rho} vertex can be investigated in no other way. The large momentum transfer in the nonmesonic decay process suggests a means to probe short distance aspects of the interaction, possibly revealing baryon substructure effects. Whether the {Delta}I = 1/2 rule, which governs free {Lambda} decay, also applies to the nonmesonic decay process remains an open question. The free {Lambda} does not decay by emission of a {pi}{sup +}; the {pi}{sup +} decay of {sup 4}He is a puzzle. Finally, the weak decay of strangeness -2 hypernuclei is an important topic, because the pionic decay process is central to current efforts to seek and identify {Lambda}{Lambda} hypernuclei.

Using the SU6 quark-model baryon-baryon interaction recently developed by the Kyoto-Niigata group, we calculate NN, Lambda N and Sigma N G-matrices in ordinary nuclear matter. This is the first attempt to discuss the Lambda and Sigma single-particle potentials in nuclear medium, based on the realistic quark-model potential. The Lambda potential has the depth of more than 40 MeV, which is more attractive than the value expected from the experimental data of Lambda-hypernuclei. The Sigma potential turns out to be repulsive, the origin of which is traced back to the strong Pauli repulsion in the Sigma N (I=3/2) ^3S_1 state.

The inclusive process of the neutrinoless muon-to-electron conversion in nuclei is investigated by using the renormalized quasiparticle random-phase approximation (RQRPA). This approach is an improvement of the ordinary QRPA which restores the Pauli principle. It is a more reliable method for extremely small transition matrix elements as for the (μ−,e−) conversion. Our calculations refer to a set of nuclei throughout the periodic table but we specifically investigate those isotopes for which experiments are done or planned. We study in particular 48 Ti which is at present used as a target at PSI in the new ongoing μ−e conversion experiment with the SINDRUM II spectrometer.

Exact expressions of the Pauli exclusion operator Q in the nuclear matter calculation are presented in detail. Exact formulae are also given for the calculations of the single-particle-potential energy and the binding energy per nucleon with the exact Q operator. Numerical calculations of the G matrix in the lowest-order Brueckner theory are carried out to check the reliability of the standard angle-average approximation for the Q operator by employing the Bonn B and C NN potentials. It is observed that the exact treatment of the operator Q brings about non-negligible and attractive contributions to the binding energy., 16 pages, 3 figures

d' dibaryon masses and radii are calculated in a colored quark cluster model. The complications due to the Pauli principle are properly taken into account within the Resonating Group Method (RGM). The effect of Bose-Einstein condensation of dibaryons on the equation of state and possible astrophysical consequences are discussed.

A critical review is given of the features of 12 C + 12 C elastic scattering at low energies (Ecm ⩽ 37.5 MeV) which may be ascribed to a mean field, or optical potential, and how this field matches smoothly on to optical model descriptions of the scattering at higher energies (Ecm from 35 to 725 MeV). In particular we examine the proposed shape resonance band at low energy and show that it follows naturally from the use of a deep optical potential such as is required at higher energy. Furthermore we show that such a potential results in radial wavefunctions with sufficient numbers of nodes to satisfy the requirements of the Pauli principle under antisymmetrization. The reported reaction cross section data appear to be too small and inconsistent with the elastic cross sections measured in the same energy range; in addition, their oscillations with energy are too large in amplitude to be ascribed to spherical mean field effects. Some discussion is also given of the bound states implied by these potentials and their relation to a cluster model of 24Mg.

We extend our previous exotic cluster treatment of heavy even-even nuclei by modelling 223 Ra as a 208 Pb + 14 C + n system. The neutron occupies 1 g 9 2 , 0i 11 2 , 0j 15 2 , 2d 5 2 , 3s 1 2 , 1g 7 2 and 2d 3 2 states with energies taken from the known spectrum of 209 Pb, while the 14 C cluster occupies 0 + , 2 + , 4 + , … or 1 − , 3 − , 5 − , … states whose energies are taken from the known levels of 222 Ra. The 14 C-n interaction mixes together the various combinations of neutron and 14 C orbital motion states coupled to total angular momentum I . Diagonalization of the Hamiltonian matrices for each I -state then yields energies and eigenvectors for comparison with experimental data. Once the Pauli principle has been satisfied by excluding the odd neutron from orbitals already occupied by neutrons in the 14 C cluster we generate low-lying bands with K π values (in order of increasing energy) 3 2 + , 3 2 + , 5 2 + , 5 2 + , 1 2 + and 1 2 + . We calculate strong E2 transitions (∼100 W.u.) within a given band, and much weaker ones (≲1 W.u.) between different K -bands. We give a good account of the relatively strong E1 transitions between bands of equal K but opposite parity (≲0.001 W.u.) and the much weaker ones ( −4 W.u.) between opposite parity bands with different values of K . Our description of in-band M1 transitions is in good accord with the data, and we predict equally strong cross-band transitions. Our calculation indicates that the ground state of 223 Ra is constructed principally from a 0i 11 2 neutron coupled to the 208 Pb 14 C relative motion, in qualitative agreement with the observation that the exotic decay of 223 Ra goes preferentially to the first excited state of 209 Pb with spin 11 2 + .