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A dynamical coupled-channels (DCC) model for neutrino-nucleon reactions in the resonance region is developed. Starting from the DCC model that we have previously developed through an analysis of πN,γN→πN,ηN,KΛ,KΣ reaction data for W≤2.1 GeV, we extend the model of the vector current to Q2≤3.0 (GeV/c)2 by analyzing electron-induced reaction data for both proton and neutron targets. We derive axial-current matrix elements that are related to the πN interactions of the DCC model through the partially conserved axial current (PCAC) relation. Consequently, the interference pattern between resonant and nonresonant amplitudes is uniquely determined. We calculate cross sections for neutrino-induced meson productions, and compare them with available data. Our result for the single-pion production reasonably agrees with the data. We also make a comparison with the double-pion production data. Our model is the first DCC model that can give the double-pion production cross sections in the resonance region. We also make comparison of our result with other existing models to reveal an importance of testing the models in the light of PCAC and electron reaction data. The DCC model developed here will be a useful input for constructing a neutrino-nucleus reaction model and a neutrino event generator for analyses of neutrino experiments. [ABSTRACT FROM AUTHOR]

We investigate the model dependence of meson resonance properties extracted from the Dalitz-plot analysis of the three-pions photo-production reactions on the nucleon. Within a unitary model developed in our earlier work, 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 a three-body unitarity condition. [ABSTRACT FROM AUTHOR]

As a first step toward developing a reaction model that enables a comprehensive description of neutrino-nucleon reactions in the nucleón resonance region, we have applied for the first time a dynamical coupled-channels model, which successfully describes πN, γN → πN, ηN, ππN, KΛ, and AΣ reactions 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 Q² = 0 to the πN → X reaction amplitudes through the partially conserved axial current hypothesis. We present the contributions from each of the πN, πN, ππN, KΛ, and KΣ channels to the F2 structure function at the Q² → 0 limit up to W = 2 GeV. [ABSTRACT FROM AUTHOR]

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), π2 (1670), π2 (2100), and D0 mesons, and show that the Z-diagram mechanisms can contribute 1o the calculated Dalitz plot distributions by as much as 30% in magnitudes in the regions where f0;0(600), ρ(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 Cabibbo-Kobayashi-Maskawa 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. [ABSTRACT FROM AUTHOR]

The recent LHCb data on B0s→J/ψp̅p revealed a new pentaquark-like Pc(4337)+ structure, while finding no evidence for Pc(4312)+ discovered earlier in Λ0b→J/ψpK-. Though puzzling, the data actually offer an important hint to understand the nature of the pentaquark candidates. We develop a model to analyze the B0s→J/ψp̅p data. We find that a Σc̅D one-loop mechanism causes a threshold cusp that fits well the Pc(4337)+ peak. Also, the Σc̅D and Λc̅D* threshold cusps interfere with each other to reproduce an oscillating behavior in the proton helicity angle distribution. These results combined with our earlier analysis on Λ0b→J/ψpK- indicate that Pc(4312)+ and Pc(4337)+ are created by different interference patterns between the Σc̅D and Λc̅D* (anomalous) threshold cusps. The proposed scenario consistently explains why the Pc(4312)+ and Pc(4337)+ peaks appear in Λ0b→J/ψpK- and B0s→J/ψp̅p, respectively, but not vice versa or both. [ABSTRACT FROM AUTHOR]

Zc(4430) discovered by the Belle Collaboration and confirmed by the LHCb Collaboration in B0→ψ(2S)K-π+ is generally considered to be a charged charmoniumlike state that includes minimally two quarks and two antiquarks. Zc(4200) found in B0→J/ψK-π+ by Belle is also a good candidate of a charged charmoniumlike state. In this work, we propose a compelling alternative to the tetraquark-based interpretations of Zc(4430) and Zc(4200). We demonstrate that kinematical singularities in triangle loop diagrams induce a resonancelike behavior that can consistently explain the properties (spin parity, mass, width, and Argand plot) of Zc(4430) and Zc(4200) from the experimental analyses. Applying this idea to Λ0b→J/ψpπ-, we also identify triangle singularities that behave like Zc(4200), but no triangle diagram is available for Zc(4430). This is consistent with LHCb's finding that their description of the Λ0b→J/ψpπ- data is significantly improved by including a Zc(4200) contribution while Zc(4430) seems to hardly contribute. Even though the proposed mechanisms have uncertainty in the absolute strengths which are currently difficult to estimate, otherwise the results are essentially determined by the kinematical effects and, thus, robust. [ABSTRACT FROM AUTHOR]

The current and near-future neutrino-oscillation experiments require significantly improved neutrino-nucleus reaction models. Neutrino-nucleon pion production data play a crucial role to validate corresponding elementary amplitudes that go into such neutrino-nucleus models. Thus, the currently available data extracted from charged-current neutrino-deuteron reaction data (νμd→μ¯πNN) must be corrected for nuclear effects such as the Fermi motion and final state interactions (FSI). We study νμd→μ¯πNN with a theoretical model including the impulse mechanism supplemented by FSI from NN and πN rescatterings. An analysis of the spectator momentum distributions reveals that the FSI effects significantly reduce the spectra over the quasifree peak region and leads to a useful recipe to extract information of elementary νμN→μ¯πN processes using νμd→μ¯πNN data, with the important FSI corrections taken into account. We provide νμN→μ¯πN total cross sections by correcting the deuterium bubble chamber data for the FSI and Fermi motion. The results will bring a significant improvement on neutrino-nucleus reaction models for the near-future neutrino-oscillation experiments. [ABSTRACT FROM AUTHOR]

The study of pion production in nuclei is important for signal and background determinations in current and future neutrino oscillation experiments. The first step, however, is to understand the pion production reactions at the free nucleon level. We present an exhaustive study of the charged-current and neutral-current neutrino and antineutrino pion production off nucleons, paying special attention to the angular distributions of the outgoing pion. We show, using general arguments, that parity violation and time-reversal odd correlations in the weak differential cross sections are generated from the interference between different contributions to the hadronic current that are not relatively real. Next, we present a detailed comparison of three state-of-the-art, microscopic models for electroweak pion production off nucleons, and we also confront their predictions with polarized electron data, as a test of the vector content of these models. We also illustrate the importance of carrying out a comprehensive test at the level of outgoing pion angular distributions, going beyond comparisons done for partially integrated cross sections, where model differences cancel to a certain extent. Finally, we observe that all charged and neutral current distributions show sizable anisotropies, and identify channels for which parity-violating effects are clearly visible. Based on the above results, we conclude that the use of isotropic distributions for the pions in the center of mass of the final pion-nucleon system, as assumed by some of the Monte Carlo event generators, needs to be improved by incorporating the findings of microscopic calculations. [ABSTRACT FROM AUTHOR]