Publications (36)111.26 Total impact
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ABSTRACT: Within a multichannels multiresonances reaction model of pion nucleon reactions, we examine the properties of the nucleon resonances with masses less than 2GeV. The Roper resonance and the second resonance in P 11 are found to evolve dynamically from the same bare state. With the exception of the P 13 and P 31 resonances, our resonance pole positions agree well with the 3 and 4 star resonances listed by the Particle Data Group.  [Show abstract] [Hide abstract]
ABSTRACT: We show that two almost degenerate poles near the $$\pi${}$\Delta${}$ threshold and the next higher mass pole in the ${P}_{11}$ partial wave of $$\pi${}N$ scattering evolve from a single bare state through its coupling with $$\pi${}N$, $$\eta${}N$, and $$\pi${}$\pi${}N$ reaction channels. This finding provides new information on understanding the dynamical origins of the Roper ${N}^{*}(1440)$ and ${N}^{*}(1710)$ resonances listed by Particle Data Group. Our results for the resonance poles in other $$\pi${}N$ partial waves are also presented.  [Show abstract] [Hide abstract]
ABSTRACT: A comprehensive study of the meson production reactions with initial piN, gammaN, and N(e,e') based on a dynamical coupledchannels approach is being made to explore the structure of the N^* states in the Excited Baryon Analysis Center (EBAC) at Jefferson Lab. In this talk we present a current status of our study of the photo and electroproduction reactions, particularly focusing on the single and double pion production reactions. We will also discuss what impact the socalled ``completemeasurement'' of single pseudoscalar meson photoproduction reactions has on the construction of reaction models, which is a key to the precise determination of the N* properties.  [Show abstract] [Hide abstract]
ABSTRACT: The nucleon resonances appear as poles of the scattering amplitudes on the complex energy plane. The masses of N^* and the electromagnetic NN^* transition form factors are obtained from the pole positions and the residues of the scattering amplitudes. We have developed a method of analytic continuation to extract resonance parameters from the amplitudes of the dynamical reaction model, which includes unstable particle channels such as pi,N and rhoN. We apply the method for the piN and &*circ;N amplitudes from our coupled channel model of meson production reactions. The extracted NN^* form factors for a few N^* resonances will be presented.  [Show abstract] [Hide abstract]
ABSTRACT: Within a dynamical coupledchannels model which has already been fixed from analyzing the data of the pi N > pi N and gamma N > pi N reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, W< 1.7 GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects due to the direct gamma N > pi pi N mechanism, the interplay between the resonant and nonresonant amplitudes, and the coupledchannels effects. The model parameters which can be determined most effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies. Comment: Version to appear in PRC. 16 pages, 13 figures  [Show abstract] [Hide abstract]
ABSTRACT: We have performed a dynamical coupledchannels analysis of available p(e,e(')pi)N data in the region of W <= 1.6 GeV and Q(2)<= 1.45 (GeV/c)(2). The channels included are gamma N*, pi N, eta N, and pi pi N that has pi Delta, rho N, and sigma N components. With the hadronic parameters of the model determined in our previous investigations of pi N >pi N, pi pi N reactions, we have found that the available data in the considered W <= 1.6 GeV region can be fitted well by only adjusting the bare gamma N*> N* helicity amplitudes for the lowest N* states in P33, P11, S11, and D13 partial waves. The sensitivity of the resulting parameters to the amount of data included in the analysis is investigated. The importance of coupledchannels effect on the p(e,e(')pi)N cross sections is demonstrated. The meson cloud effect, as required by the unitarity conditions, on the gamma N*> N* form factors are also examined. Necessary future developments, both experimentally and theoretically, are discussed.  [Show abstract] [Hide abstract]
ABSTRACT: Within the relativistic quantum field theory, we analyze the differences between the $\pi N$ reaction models constructed from using (1) threedimensional reductions of BetheSalpeter Equation, (2) method of unitary transformation, and (3) timeordered perturbation theory. Their relations with the approach based on the dispersion relations of Smatrix theory are dicusssed. 
Article: Coupledchannel analysis of hadronic and electromagnetic pi, eta, twopi production reactions
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ABSTRACT: Recent high precision data of the electromagnetic meson production reactions off nucleons from Bonn, GRAAL, JLab, Mainz and Spring8 make possible to extract Q^2 dependence of the electromagnetic NN^* transition form factors. To extract such information on the quarkgluon structures of the N^* states, a comprehensive analysis of the hadronic and electromagnetic meson production reactions is ongoing in Excited Baryon Analysis Center (EBAC) at JLab. The analysis is based on the dynamical coupledchannel model which properly describes correlations among all relevant reaction channels required from unitarity and can treat nonresonant and resonant processes in a unified manner. In this talk, we will report current status on the analysis of gammaN >piN, gammaN >etaN and e N >e' piN reactions. The main purpose is to determine parameters associated with the electromagnetic interactions by this combined analysis of the electromagnetic meson production reactions. We will also discuss the NN^* electromagnetic form factors extracted from the analysis of the e N >e' piN reaction.  [Show abstract] [Hide abstract]
ABSTRACT: As a step toward performing a complete coupledchannels analysis of the world data of pi N, gamma^* N > pi N, eta N, pi pi N reactions, the pi N > pi pi N reactions are investigated starting with the dynamical coupledchannels model developed in Phys. Rev. C76, 065201 (2007). The channels included are pi N, eta N, and pi pi N which has pi Delta, rho N, and sigma N resonant components. The nonresonant amplitudes are generated from solving a set of coupledchannels equations with the mesonbaryon potentials defined by effective Lagrangians. The resonant amplitudes are generated from 16 bare excited nucleon (N^*) states which are dressed by the nonresonant interactions as constrained by the unitarity condition. The data of total cross sections and pi N and pi pi invariant mass distributions of pi^+ p > pi^+ pi^+ n, pi^+ pi^0p and pi^ p > pi^+ pi^ n, pi^ pi^0 n, pi^0 pi^0 n reactions from threshold to the invariant mass W = 2 GeV can be described to a very large extent. We show the importance of the coupledchannels effects and the strong interference between the contributions from the pi Delta, sigma N, and rho N channels. The large interference between the resonant and nonresonant amplitudes is also demonstrated. Possible future developements are discussed.  [Show abstract] [Hide abstract]
ABSTRACT: The electromagnetic pion production reactions are investigated within the dynamical coupledchannels model developed in {\bf Physics Reports, 439, 193 (2007)}. The mesonbaryon channels included in this study are $\gamma N$, $\pi N$, $\eta N$, and the $\pi\Delta$, $\rho N$ and $\sigma N$ resonant components of the $\pi\pi N$ channel. With the hadronic parameters of the model determined in a recent study of $\pi N$ scattering, we show that the pion photoproduction data up to the second resonance region can be described to a very large extent by only adjusting the bare $\gamma N \to N^*$ helicity amplitudes, while the nonresonant electromagnetic couplings are taken from previous works. It is found that the coupledchannels effects can contribute about 10  20 % of the production cross sections in the $\Delta$ (1232) resonance region, and can drastically change the magnitude and shape of the cross sections in the second resonance region. The importance of the offshell effects in a dynamical approach is also demonstrated. The meson cloud effects as well as the coupledchannels contributions to the $\gamma N \to N^*$ form factors are found to be mainly in the low $Q^2$ region. For the magnetic M1 $\gamma N \to \Delta$ (1232) form factor, the results are close to that of the SatoLee Model. Necessary improvements to the model and future developments are discussed.  [Show abstract] [Hide abstract]
ABSTRACT: As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupledchannels model, developed in Physics Reports 439, 193 (2007), are determined by fitting the πNscattering data. The channels included in the calculations are πN,ηN, and ππN, which has πΔ,ρN, and σN resonant components. The nonresonant mesonbaryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of S,P,D, and F partial waves are included to generate the resonant amplitudes in the fits. The parameters of the model are first determined by fitting as much as possible the empirical πN elasticscattering amplitudes of SAID up to 2 GeV. We then refine and confirm the resulting parameters by directly comparing the predicted differential cross section and target polarization asymmetry with the original data of the elastic π±p→π±p and chargeexchange πp→π0n processes. The predicted total cross sections of πN reactions and πN→ηN reactions are also in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future developments are discussed. 
Article: Dynamical CoupledChannel Model of $\pi N$ Scattering in the W $\leq$ 2 GeV Nucleon Resonance Region
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ABSTRACT: As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupledchannel model, developed in {\it Physics Reports 439, 193 (2007)}, are determined by fitting the $\pi N$ scattering data. The channels included in the calculations are $\pi N$, $\eta N$ and $\pi\pi N$ which has $\pi\Delta$, $\rho N$, and $\sigma N$ resonant components. The nonresonant mesonbaryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of $S$, $P$, $D$, and $F$ partial waves are included to generate the resonant amplitudes in the fits. The parameters of the model are first determined by fitting as much as possible the empirical $\pi N$ elastic scattering amplitudes of SAID up to 2 GeV. We then refine and confirm the resulting parameters by directly comparing the predicted differential cross section and target polarization asymmetry with the original data of the elastic $\pi^{\pm} p \to \pi^{\pm} p$ and chargeexchange $\pi^ p \to \pi^0 n$ processes. The predicted total cross sections of $\pi N$ reactions and $\pi N\to \eta N$ reactions are also in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future developments are discussed. 
Article: Dynamical coupledchannel model of meson production reactions in the nucleon resonance region
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ABSTRACT: A dynamical coupledchannel model is presented for investigating the nucleon resonances in the meson production reactions induced by pions and photons. The model is based on an energyindependent Hamiltonian which is derived from a set of Lagrangians by using a unitary transformation method. By applying the projection operator techniques,we derive a set of coupledchannel equations which satisfy the unitarity conditions within the channel space spanned by the considered twoparticle mesonbaryon states and the threeparticle $\pi\pi N$ state. We present and explain in detail a numerical method based on a splinefunction expansion for solving the resulting coupledchannel equations which contain logarithmically divergent oneparticleexchange driving terms resulted from the $\pi\pi N$ unitarity cut. We show that this driving term can generate rapidly varying structure in the reaction amplitudes associated with the unstable particle channels. It also has large effects in determining the twopion production cross sections. Our results indicate that cautions must be taken to interpret the $N^*$ parameters extracted from using models which do not include $\pi\pi N$ cut effects.  [Show abstract] [Hide abstract]
ABSTRACT: It is shown that most of the models for analyzing mesonbaryon reactions in the nucleon resonance region can be derived from a Hamiltonian formulation of the problem. An extension of the coupledchannel approach to include $\pi\pi N$ channel is briefly described and some preliminary results for the $N^*(1535)$ excitation are presented.  [Show abstract] [Hide abstract]
ABSTRACT: We have studied the behaviour of Smatrix poles near the thresholds for some threebody systems. In Amado's simple model for three bosons with an attractive Swave twobody interaction and specetor angular momentum l=0, the Smatrix pole behaves as Im E ∞ (ReE)2 near the threshold in the fourth quadrant of the unphysical complex Eplane. This behaviour is formally the same as that in the twobody scattering with angular momentum l=3/2 and a threebody resonance shows up near the threshold. In such a case, the Fredholm determinant of the Faddeev equation at zero energy, DF(0), is close to zero. However, it is shown that the value DF(0) does not definitely tell us whether the system is attractive or repulsive in contrast to the case of a twobody system. As physical applications, we have studied Lambdann and Sigmann systems. The Smatrix poles are found to be far away from the physical real axis and do not give rise to observable effects for the twobody interactions reproducing the lowenergy scattering data, although the Lambdann system could develop a threebody resonance if the Lambdan interaction were slightly more attractive.  [Show abstract] [Hide abstract]
ABSTRACT: The π+d ↔ pp reaction is studied within a unitary mesonexchange πNN model which was developed in our previous studies of NN and πd scattering. The predicted total cross sections are about of the data in the Δ resonance region. The calculated amplitudes in Jπ = 2+, 3− channels reproduce the resonant counterclockwise behavior of Bugg's amplitude analysis. The predicted pp → πd angular distributions and analyzing powers are, however, only in qualitative agreement with the data. The dynamical content of our calculations is analyzed and compared with some of the previous approaches.  [Show abstract] [Hide abstract]
ABSTRACT: The probabilities of hypernucleus formation by K capture at rest are calculated in the bound state approximation for a wide range of target nuclei, i.e. 4He, 12C, 16O, 40Ca, 90Zr and 208Pb. The mass number dependence of the formation probabilities, the relative populations of the various states in the same nucleus and the effects of kaon and pionoptical potentials are studied in detail. K capture at rest seems less selective in populating hypernucleus states than other reactions such as (K, pi/+) in flight and (pi+/, K+). 
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ABSTRACT: Within a unitary piNN theory a set of coupled integral equations defined in the NN⊕NDelta ⊕piNN subspace has been derived for examining the extent to which the NN and pid elastic scattering data can be both described by a class of mesonexchange piNN models. The considered models are constructued by using a previously developed subtraction procedure to extend the Paris, Bonn, ArgonneV14, and Reid NN potentials to include the coupling to the piNN production channel. The pion production through the Delta excitation is described by a piN&lrarr2;Delta vertex and a VNN&lrarr2;NDelta transition potential, while the production through nonresonant piN interactions is described by a transition operator FpiNN&lrarr2;NN. It is found that none of the constructed models can accurately reproduce all NN and pid elastic scattering data, in particularly the data of polarization observables. Our results indicate that either the conventional phenomenological parametrizations of baryonbaryon interaction at short distances are not valid in the intermediate energy region, or some genuine quark dynamics has already been revealed in the piNN data.  [Show abstract] [Hide abstract]
ABSTRACT: The relativistic stripping model is presented for the (p, pi+) reaction in the Deltaresonance region. The Dirac impulse approximation and a DiracHartree calculation are used for the proton nucleus interaction and neutron bound state wave function respectively. The Deltahole model is employed for the pionnucleus interaction. This model is applied to the reaction 16O(p, pi+)17O(g.s.).
Publication Stats
864  Citations  
111.26  Total Impact Points  
Top Journals
 Physical Review C (12)
 Nuclear Physics A (6)
 Physics Letters B (4)
 FewBody Systems (1)
 Physics Reports (1)
Institutions

19872010

Shizuoka University
 Department of Physics
Sizuoka, Shizuoka, Japan


2004

Argonne National Laboratory
Lemont, Illinois, United States


1986

TRIUMF
Vancouver, British Columbia, Canada


19851986

Swiss Institute for Art Research
Zürich, Zurich, Switzerland


19811984

The University of Tokyo
 Department of Physics
Tōkyō, Japan
