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H. Kamada

Publications and source records attributed to H. Kamada.

At least 127 records · Page 7Linked to original sources
arXiv2000

Extraction of electromagnetic neutron form factors through inclusive and exclusive polarized electron scattering on polarized 3He target

Inclusive 3He(e,e') and exclusive 3He(e,e'n) processes with polarized electrons and 3He have been theoretically analyzed and values for the magnetic and electric neutron form factors have been extracted. In both cases the form factor values agree well with the ones extracted from processes on the deuteron. Our results are based on Faddeev solutions, modern NN forces and partially on the incorporation of mesonic exchange currents.

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arXiv2000

The three- and four-nucleon systems from chiral effective field theory

Recently developed chiral nucleon-nucleon (NN) forces at next-to-leading order (NLO) that describe NN phase shifts up to about 100 MeV fairly well have been applied to 3N and 4N systems. Faddeev-Yakubovsky equations have been solved rigorously. The chiral NLO forces depend on a momentum cut-off Λlying between 540-600 MeV/c. The resulting 3N and 4N binding energies are in the same range as found using standard NN potentials. In additon, low-energy 3N scattering observables are very well reproduced like for standard NN forces. Surprisingly, the long standing A_y-puzzle is resolved at NLO. The cut-off dependence of the scattering observables is rather mild.

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arXiv2000

Faddeev Calculations of Proton-Deuteron Radiative Capture with Exchange Currents

pd capture processes at various energies have been analyzed based on solutions of 3N-Faddeev equations and using modern NN forces. The application of the Siegert theorem is compared to the explicit use of $π$- and $ρ$-like exchange currents connected to the AV18 NN interaction. Overall good agreement with cross sections and spin observables has been obtained but leaving room for improvement in some cases. Feasibility studies for 3NF's consistently included in the 3N continuum and the 3N bound state have been performed as well.

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arXiv2000

Modern nuclear force predictions for the alpha particle

We present new calculations of the $α$-particle which are based on the most modern nucleon-nucleon interactions alone and combined with the Tucson-Melbourne or the Urbana IX three-nucleon interaction. Results for the binding energies and some properties of the wavefunction are given. On that phenomenological level little room is left for the action of a possible four-nucleon force.

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arXiv2000

Realistic Ghost State : Pauli Forbidden State from Rigorous Solution of the Alpha Particle

The antisymmetrization of the composite particles in cluster model calculations manifests itself in Pauli forbidden states (ghost states), if one restricts oneself on undeformed cluster in the low energy region. The resonating group method and the generating coordinate method rely on a property of the norm kernel, which introduces some of the ghost states. The norm kernel has been usually calculated under the assumption that the inner wavefunctions have a simple Gaussian form. It is the first time that this assumption is tested by the rigorous way. In the 4He+N system, we demonstrate a ghost state, which is calculated from a rigorous solution of Yakubovsky equations for the alpha particle. The ghost states calculated by rigorous and approximate methods turn out to have a very similar form. It is analytically proved that the trace of the norm kernel does not depend on the inner wavefunction we choose.

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arXiv2000

A Model for the 3He(\vec d, p)4He Reaction at Intermediate Energies

Polarization correlation coefficients have been measured atRIKEN for the \vec 3He(\vec d,p)4He reaction at intermediate energies. We propose a model for the (\vec d, p) reaction mechanism using the pd elastic scattering amplitude which is rigorously determined by a Faddeev calculation and using modern NN forces. Our theoretical predictions for deuteron polarization observables A_y, A_{yy}, A_{xx} and A_{xz} at E_d=140, 200 and 270 MeV agree qualitatively in shape with the experimental data for the reaction 3He(\vec d,p)4He.

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arXiv1999

A Practical Method for Relativistic 3N-Scattering Calculations with Realistic Potentials

Using a scale transformation in momentum space a phase equivalent relativistic potential is generated from the nonrelativistic potential. By that transformation a practical method for the relativistic 3N scattering with realistic nucleon-nucleon potentials is introduced. The formalism can be applied to any realistic nonrelativistic potential. We also discuss the locations of the moving logarithmic singularities of the free relativistic three-body Green's function. It enters in the relativistic 3N Faddeev equations, which have been formulated long time ago for a 3-boson bound state and which we propose to also use for 3N scattering. Finally we compare relativistic deuteron wave functions to nonrelativistic ones.

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arXiv1999

Investigation of the Exclusive 3He(e,e'pp) Reaction

Cross sections for the 3He(e,e'pp)n reaction were measured at an energy transfer of 220 MeV and three-momentum transfers q of 305, 375, and 445 MeV/c. Results are presented as a function of q and the final-state neutron momentum for slices in specific kinematic variables. At low neutron momenta, comparison of the data to results of continuum Faddeev calculations performed with the Bonn-B nucleon-nucleon potential indicates a dominant role for two-proton knockout induced by a one-body hadronic current.

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arXiv1999

Inclusive Scattering of Polarized Electrons on Polarized 3He Effects of Final State Interaction and the Magnetic Form Factor of the Neutron

Effects of final state interaction on asymmetries in inclusive scattering of polarized electrons on polarized 3He are investigated using consistent 3He bound state wave function and 3N continuum scattering states. Significant effects are found, which influence the extraction of the magnetic neutron form factor from A_T'. The enhancement found experimentally for A_TL' near the 3N breakup threshold, which could not be explained in calculations carried through in plane wave impulse approximation up to now, occurs now also in theory if the full final state interaction is included.

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arXiv1999

The c-term of the TM 3-body Force: to be or not to be

In Faddeev calculations of ^3Hwe study the dependence of the binding on the three nucleon force. We adopt the 2 pi -exchange Tucson-Melbourne three-nucleon force and investigate phenomenologically the dependence on the strength of the individual three-body force operators (a -, b -, c - and d -terms). While the a -term provides a tiny contribution the b - and d -terms provides a tiny contribution the b - and d -terms are important to gain the experimental binding energy. We find two solutions for the c -term, one around the value used in the Tucson-Melbourne model and a new one close to zero, which supports the recentrecommendation of chiral perturbation theory that the short-range c -term should be dropped.

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arXiv1999

Partial Wave Decomposition for Meson Exchange Currents in Few-Nucleon Systems

We develop an approach for calculating matrix elements of meson exchange currents between 3N basis states in (jJ)-coupling and a 3N bound state. The contribution generated by $π$- and $ρ$-exchange are included in the consideration. The matrix elements are expressed in terms of multiple integrals in the momentum space. We apply a technique of the partial wave decompositions and carry out some angular integrations in closed form. Different representations appropriate for numerical calculations are derived for the matrix elements of interest. The momentum dependences of the matrix elements are studied and benchmark results are presented. The approach developed is of interest for the investigations of deuteron- proton radiative capture and ^3He photo- and electrodisintegration when the interaction in the initial or final nuclear states is taken into account by solving the Faddeev equations.

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arXiv1999

A Momentum Transformation Connecting a NN Potential in the Nonrelativistic and the Relativistic Two-Nucleon Schroedinger Equation

An analytical relation between center of mass momenta in a nonrelativistic and a relativistic two-nucleon Schrödinger equation is proposed which allows to analytically rewrite the two Schrödinger equations into each other. As a consequence a NN potential occurring in the relativistic Schrödinger equation can be gained from a nonrelativistic one by an analytical procedure. The S-matrices in the two equations are exactly identical and therefore the two-nucleon phase shifts.

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arXiv1999

On the Impossibility to Measure the Total Neutron- and Proton Induced Nonmesonic Decays for Hypertriton

Based on realistic calculations for the nonmesonic decay rate of Hypertriton we demonstrate, that in principle it is not possible to measure the total n- and p- induced decay rates and as a consequence $Γ_n /Γ_p$ for that lightest hypernucleus.For the nonmesonic decay process the calculations are performed with modern YN forces based on various meson exchanges and taking the final state interaction among the three nucleons fully into account. Our findings have consequences also for the interpretation of experimental $Γ_n/Γ_p$ ratios for heavier hypernuclei where severe discrepancies exist to theoretical $Γ_n/Γ_p$ ratios.

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arXiv1999

Modern NN Force Predictions for the Total ND Cross Section up to 300 MeV

For several modern nucleon-nucleon potentials state-of-the-art Faddeev calculations are carried out for the $nd$ total cross section between 10 and 300 MeV projectile energy and compared to new high precision measurements. The agreement between theory and data is rather good, with exception at the higher energies where a 10% discrepancy builds up. In addition the convergence of the multiple scattering series incorporated in the Faddeev scheme is studied numerically with the result, that rescattering corrections remain important. Based on this multiple scattering series the high energy limit of the total $nd$ cross section is also investigated analytically. In contrast to the naive expectation that the total $nd$ cross section is the sum of the $np$ and $nn$ total cross sections we find additional effects resulting from the rescattering processes, which have different signs and different behavior as function of the energy. A shadowing effect in the high energy limit only occurs for energies higher than 300 MeV. The expressions in the high energy limit have qualitatively a similar behavior as the exactly calculated expressions, but can be expected to be valid quantitatively only at much higher energies.

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arXiv1998

Scaling properties of the longitudinal and transversal asymmetries of the $\vec{n}\vec{d}$ total cross section

The longitudinal and transversal asymmetries of the total $\vec{n}\vec{d}$ cross section are calculated. Four modern nucleon-nucleon interactions: AV18, CD Bonn, NijmI and NijmII, give different predictions for these observables. When the three-nucleon Hamiltonian is supplemented by the $2π$-exchange Tucson-Melbourne three-nucleon force (3NF), individually adjusted with each particular NN potential to reproduce the experimental triton binding energy, all predictions practically coincide. We propose to check this scaling behavior experimentally in order to get a clear signal for 3NF effects in the low energy three-nucleon continuum. Connected to that is the proposal to measure the energy at which the longitudinal asymmetry goes through zero. This energy is shifted by about 400 keV when 3NF's are acting.

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arXiv1998

Shadowing and Antishadowing Effects in a Model for the n+d Total Cross Section

Based on the multiple scattering series incorporated in the Faddeev scheme the high energy limit of the total n+d cross section is evaluated in a nonrelativistic model system where spins are neglected. In contrast to the naive expectation that the total n+d scattering cross section is the sum of two NN cross sections we find two additional effects resulting from rescattering processes. These additional terms have different signs (shadowing and antishadowing) and a different behavior as function of the energy. Our derivation of these results which are already known from Glauber theory is based on the analytical evaluation of elastic transition amplitudes in the high energy limit. It does not depend on the diffraction type assumptions connected with Glauber theory. In this model of spinless Yukawa type forces (with no absorption) the total n+d cross section does not approach twice the NN total cross section in the high energy limit but rather approaches the total NN cross section multiplied by a number larger than two. Therefore, the enhancement effect resulting from rescattering is larger than the shadowing effect, which decreases faster with energy.

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arXiv1998

Weak capture of protons by protons

The cross section for the proton weak capture reaction $^1H(p,e^+ν_e)^2H$ is calculated with wave functions obtained from a number of modern, realistic high-precision interactions. To minimize the uncertainty in the axial two-body current operator, its matrix element has been adjusted to reproduce the measured Gamow-Teller matrix element of tritium $β$ decay in model calculations using trinucleon wave functions from these interactions. A thorough analysis of the ambiguities that this procedure introduces in evaluating the two-body current contribution to the pp capture is given. Its inherent model dependence is in fact found to be very weak. The overlap integral $Λ^2(E=0)$ for the pp capture is predicted to be in the range 7.05--7.06, including the axial two-body current contribution, for all interactions considered.

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