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H. Kamano

Publications and source records attributed to H. Kamano.

At least 37 records · Page 2Linked to original sources
arXiv2013

Recent results on N* spectroscopy with ANL-Osaka dynamical coupled-channels approach

We report our recent effort on the extraction of N*- and Delta*-resonance parameters (pole masses, coupling constants, etc.) through the comprehensive analysis of pion- and photon-induced pi N, eta N, K Lambda, and K Sigma production reactions. The analysis was performed with the ANL-Osaka dynamical coupled-channels approach, which satisfies the multichannel unitarity of the S-matrix in the channel space spanned by pi N, eta N, K Lambda, K Sigma, and also three-body pi pi N that contains rho N, pi Delta, and sigma N resonant components. Ongoing projects and future plans are also discussed.

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arXiv2013

Nucleon resonances within a dynamical coupled-channels model of pi N and gamma N reactions

The nucleon resonances are investigated within a dynamical coupled-channels model of pi N and gamma N reactions up to the invariant mass W = 2 GeV. The meson-baryon (MB) channels included in the calculations are MB = pi N, eta N, K Lambda, K Sigma, and pi pi N that has pi Delta, rho N, and sigma N resonant components. The meson-baryon amplitudes T_{M'B',MB}(W) are calculated from solving a set of coupled-channels integral equations defined by an interaction Hamiltonian consisting of (a) meson-exchange interactions v_{M'B',MB} derived from phenomenological Lagrangian, and (b) vertex interactions N* --> MB for describing the transition of a bare excited nucleon state N* to a channel MB. The parameters of v_{M'B',MB} are mainly constrained by the fit to the data of pi N --> pi N in the low energy region up to W =1.4 GeV. The bare masses of N* and the N* --> MB parameters are then determined in simultaneous fits to the data of pi N --> pi N up to W =2.3 GeV and those of pi N --> eta N, K Lambda, K Sigma and gamma N --> pi N, eta N, K Lambda, K Sigma up to W = 2.1 GeV. The pole positions and residues of nucleon resonances are extracted by analytically continuing the meson-baryon amplitudes T_{M'B',MB}(W) to the complex Riemann energy surface. From the extracted residues, we have determined the N* --> pi N, gamma N, eta N, K Lambda, K Sigma transition amplitudes at resonance poles. We compare the resonance pole positions from our analysis with those given by Particle Data Group and the recent coupled-channels analyses by the Juelich and Bonn-Gatchina groups. Four results agree well only for the first N* in each spin-parity-isospin (J^P,I) channel. For higher mass states, the number of states and their resonance positions from four results do not agree well. We discuss the possible sources of the discrepancies and the need of additional data from new hadron facilities such as J-PARC.

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arXiv2013

Toward Construction of the Unified Lepton-Nucleus Interaction Model from a Few Hundred MeV to GeV Region

Next generation neutrino oscillation experiments will need a quantitative understanding of neutrino-nucleus interaction far better than ever. Kinematics covered by the relevant neutrino-nucleus interaction spans wide region, from the quasi-elastic, through the resonance region, to the deeply inelastic scattering region. The neutrino-nucleus interaction in each region has quite different characteristics. Obviously, it is essential to combine different expertise to construct a unified model that covers all the kinematical region of the neutrino-nucleus interaction. Recently, several experimentalists and theorists got together to form a collaboration to tackle this problem. In this contribution, we report the collaboration's recent activity and a goal in near future.

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arXiv2013

Neutrino-induced meson productions off nucleon at forward limit in nucleon resonance region

We study forward neutrino-induced meson production off the nucleon in the resonance region. Our calculation is based on a dynamical coupled-channels (DCC) model that reasonably describes pi (gamma) N -> pi N, eta N, K Lambda, K Sigma data in the resonance region. We apply the PCAC hypothesis to the DCC model to relate the pi N reaction amplitude to the forward neutrino reaction amplitude. In this way, we give a prediction for nu N -> pi N, pi pi N, eta N, K Lambda, K Sigma reaction cross sections. The predicted nu N -> pi pi N, eta N, K Lambda, K Sigma cross sections are, for the first time, based on a model extensively tested by data. We compare our results with those from the Rein-Sehgal model that has been very often used in the existing Monte Carlo simulators for neutrino experiments. We find a significant difference between them.

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arXiv2012

Extraction of Meson Resonances from Three-pions Photo-production Reactions

We have investigated the model dependence of meson resonance properties extracted from the Dalitz-plot analysis of the three-pions photoproduction reactions on the nucleon. Within a unitary model developed in Phys. Rev. D 84, 114019 (2011), we generate Dalitz-plot distributions as data to perform an isobar model fit that is similar to most of the previous analyses of three-pion production reactions. It is found that the resonance positions from the two models agree well when both fit the data accurately, except for the resonance poles near branch points. The residues of the resonant amplitudes extracted from the two models and by the usual Breit-Wigner procedure agree well only for the isolated resonances with narrow widths. For overlapping resonances, most of the extracted residues could be drastically different. Our results suggest that even with high precision data, the resonance extraction should be based on models within which the amplitude parametrization is constrained by three-particle unitarity condition.

hep-ph↗
arXiv2012

Pion-Exchange and Fermi-Motion Effects on the Proton-Deuteron Drell-Yan Process

Within a nuclear model that the deuteron has NN and πNN components, we derive convolution formula for investigating the Drell-Yan process in proton-deuteron (pd) reactions. The contribution from the πNN component is expressed in terms of a pion momentum distribution that depends sensitively on the πNN form factor. With a πNN form factor determined by fitting the πN scattering data up to invariant mass W = 1.3 GeV, we find that the pion-exchange and nucleon Fermi-motion effects can change significantly the ratios between the proton-deuteron and proton-proton Drell-Yan cross sections, R_{pd/pp} = σ^{pd}/(2σ^{pp}), in the region where the partons emitted from the target deuteron are in the Bjorken x_2 > 0.4 region. The calculated ratios R_{pd/pp} at 800 GeV agree with the available data. Predictions at 120 GeV for analyzing the forthcoming data from Fermilab are presented.

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arXiv2012

Neutrino-induced forward meson-production reactions in nucleon resonance region

As a first step toward developing a reaction model that enables a comprehensive description of neutrino-nucleon reactions in the nucleon resonance region, we have applied for the first time a dynamical coupled-channels model, which successfully describes πN, γN --> πN, ηN, ππN, KΛ, KΣreactions up to W = 2 GeV, to predict the neutrino-induced meson-production reactions with ΔS = 0 at the forward angle limit. This has been achieved by relating the divergence of the axial-current matrix elements at Q^2 = 0 to the πN --> X reaction amplitudes through the PCAC hypothesis. We present the contributions from each of the πN, ηN, ππN, KΛ, KΣchannels to the F_2 structure function at Q^2 --> 0 limit up to W = 2 GeV.

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arXiv2011

Unitary coupled-channels model for three-mesons decays of heavy mesons

A unitary coupled-channels model is presented for investigating the decays of heavy mesons and excited meson states into three light pseudoscalar mesons. The model accounts for the three-mesons final state interactions in the decay processes, as required by both the three-body and two-body unitarity conditions. In the absence of the Z-diagram mechanisms that are necessary consequences of the three-body unitarity, our decay amplitudes are reduced to a form similar to those used in the so-called isobar-model analysis. We apply our coupled-channels model to the three-pions decays of a1(1260), pi2(1670), pi2(2100), and D0 mesons, and show that the Z-diagram mechanisms can contribute to the calculated Dalitz plot distributions by as much as 30% in magnitudes in the regions where f0(600), rho(770), and f2(1270) dominate the distributions. Also, by fitting to the same Dalitz plot distributions, we demonstrate that the decay amplitudes obtained with the unitary model and the isobar model can be rather different, particularly in the phase that plays a crucial role in extracting the CKM CP-violating phase from the data of B meson decays. Our results indicate that the commonly used isobar model analysis must be extended to account for the final state interactions required by the three-body unitarity to reanalyze the three-mesons decays of heavy mesons, thereby exploring hybrid or exotic mesons, and signatures of physics beyond the standard model.

hep-ph↗
arXiv2011

Determining pseudoscalar meson photo-production amplitudes from complete experiments

We review the development of the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single, double and triple-polarization terms involving 16 spin-dependent observables. We examine the different conventions that have been used by different authors, and we present expressions that allow the direct numerical calculation of any pseudoscalar meson photo-production observables with arbitrary spin projections from the Chew-Goldberger-Low-Nambu amplitudes. We use this numerical tool to clarify apparent sign differences that exist in the literature. We also present analytic expressions that determine the recoil baryon polarization, together with examples of their potential use with quasi-4pi detectors to deduce observables. As an illustration of the use of the consistent machinery presented in this review, we carry out a multipole analysis of the gamma p -> K^+ Lambda reaction and examine the impact of recently published polarization measurements. In fitting multipoles, we use a combined Monte Carlo sampling of the amplitude space, with gradient minimization, and find a shallow chi^2 valley pitted with a very large number of local minima. This results in broad bands of multipole solutions that are experimentally indistinguishable. While these bands have been noticeably narrowed by the inclusion of new polarization measurements, many of the multipoles remain very poorly determined, even in sign, despite the inclusion of data on 8 different observables. We have compared multipoles from recent PWA codes with our model-independent solution bands. The potential accuracy of amplitudes that could be extracted from measurements of all 16 polarization observables has been studied with mock data using the statistical variations that are expected from ongoing experiments.

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arXiv2010

Calculations of Polarization Observables in Pseudoscalar Meson Photo-production Reactions

In preparation for the extraction of pseudoscalar meson photo-production amplitudes from a new generation of complete experiments, we assemble the relations between experimental observables and the Chew-Goldberger-Low-Nambu amplitudes. We present expressions that allow the direct calculation of matrix elements with arbitrary spin projections and uses these to clarify sign differences that exist in the literature. Comparing to the MAID and SAID analysis codes, we have found that the implied definitions of six double-polarization observables are the negative of what has been used in comparing to recent experimental data.

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arXiv2010

Extraction of P11 Resonance from pi-N Data and Its Stability

An important question about resonance extraction is how much resonance poles and residues extracted from data depend on a model used for the extraction, and on the precision of data. We address this question with the dynamical coupled-channel (DCC) model developed in Excited Baryon Analysis Center (EBAC) at JLab. We focus on the P11 pi-N scattering. We examine the model-dependence of the poles by varying parameters to a large extent within the EBAC-DCC model. We find that two poles associated with the Roper resonance are fairly stable against the variation. We also develop a model with a bare nucleon, thereby examining the stability of the Roper poles against different analytic structure of the P11 amplitude below pi-N threshold. We again find a good stability of the Roper poles.

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arXiv2010

Extraction of P11 resonances from pi N data

We show that two P11 nucleon resonance poles near the pi Delta threshold, obtained in several analyses, are stable against large variations of parameters within a dynamical coupled-channels analysis based on meson-exchange mechanisms. By also performing an analysis based on a model with a bare nucleon state, we find that this two-pole structure is insensitive to the analytic structure of the amplitude in the region below pi N threshold. Our results are M_pole = (1363^{+9}_{-6} -i79^{+3}_{-5}) MeV and (1373^{+12}_{-10} -i114^{+14}_{-9}) MeV. We also demonstrate that the number of poles in the 1.5 GeV < W < 2 GeV region could be more than one, depending on how the structure of the single-energy solution of SAID is fitted. For three-pole solutions, our best estimated result of a pole near N(1710) listed by Particle Data Group is (1829^{+131}_{-65} -i192^{+88}_{-110}) MeV which is close to the results of several previous analyses. Our results indicate the need of more accurate pi N reaction data in the W > 1.6 GeV region for high precision resonance extractions.

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arXiv2010

Disentangling the dynamical origin of P11 Nucleon Resonances

We show that two almost degenerate poles near the $πΔ$ threshold and the next higher mass pole in the $P_{11}$ partial wave of $πN$ scattering evolve from a single bare state through its coupling with $πN$, $ηN$ and $ππN$ 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 $πN$ partial waves are also presented.

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arXiv2009

Double and single pion photoproduction within a dynamical coupled-channels model

Within a dynamical coupled-channels 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 non-resonant amplitudes, and the coupled-channels 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.

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arXiv2009

Dynamical coupled-channels analysis of 1H(e,e'pi)N reactions

We have performed a dynamical coupled-channels 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 which 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 coupled-channels effect on the p(e,e' pi)N cross sections is demonstrated. The meson cloud effects, 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.

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arXiv2009

Dynamical coupled-channels study of pi N --> pi pi N reactions

As a step toward performing a complete coupled-channels 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 coupled-channels 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 non-resonant amplitudes are generated from solving a set of coupled-channels equations with the meson-baryon potentials defined by effective Lagrangians. The resonant amplitudes are generated from 16 bare excited nucleon (N^*) states which are dressed by the non-resonant 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 coupled-channels 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 non-resonant amplitudes is also demonstrated. Possible future developements are discussed.

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