Resonance production in the reactions K+p → KNπ in the intermediate energy range

Cross sections and angular distributions are presented for resonances produced in the reactions K⁺p → KNπ at momenta between 2.11 and 2.72 GeV/c. Production of K¹ (892) and Δ(1236) dominates these reactions. Some contributions from higher resonances are also found. Structures in the s-channel are discussed.     

Inelastic final-state interactions in B → VV →π K processes

We study the final-state interactions in B →π K decays through B → VV →π K processes where the inelastic rescattering occurs via single pion exchange. The next-to-leading order low-energy effective Hamiltonian and Bauer-Stech-Wirbel (BSW) model are used to evaluate the weak transition matrix elements and final-state interactions. We found that the final-state interaction effects in B →ρ K^*→π K processes are significant. The Fleischer-Mannel relation for the Cabibbo-Kobayashi-Maskawa (CKM) angle γ can be significantly modified. Received: 13 August 1998     

Low-Energy Kπ Phase Shifts in Chiral SU(3) Quark Model

The low-energy region kaon-pion S- and P-wave phase shifts with isospin I = 1/2 and I = 3/2 are dynamically studied in the chiral SU(3) quark model by solving a resonating group method equation. The model parameters are taken to be the values fitted by the energies of the baryon ground states and the kaon-nucleon elastic scattering phase shifts of different partial waves. As a preliminary study the s-channel q(-q) annihilation interactions are not included since they only act in the very short range and are subsequently assumed to be unimportant in the low-energy domain. The numerical results are in qualitative agreement with the experimental data.     

Low-Energy Kπ Phase Shifts in Chiral SU（3） Quark Model

The low-energy region kaon-pion S- and P-wave phase shifts with isospin I = 1/2 and I = 3/2 are dynamically studied in the chiral SU（3） quark model by solving a resonating group method equation. The model parameters are taken to be the values fitted by the energies of the baryon ground states and the kaon-nucleon elastic scattering phase shifts of different partial waves. As a preliminary study the s-channel qq^- annihilation interactions are not included since they only act in the very short range and are subsequently assumed to be unimportant in the low-energy domain. The numerical results are in qualitative agreement with the experimental data.     

Like pion spectra and non-linear effects in K → 3π decays

The effects of a non-linear matrix element on the like pion spectra in K → 3π decays are investigated. An effective σ model, which gives a good fit to the unlike pion spectra in all three K → 3π decays, is being used. The spectra are expressed as functions of the like pion kinetic energies, and alternatively, as functions of the Dalitz variables. Significant non-linearity is expected in the kinetic energy spectrum of the like pion as well as in the x-variable distribution in τ′ decay. The x-distribution in τ′ and K₂^o → π⁺π⁻π^o should be constant.     

K→π form factors with reduced model dependence

Using partially twisted boundary conditions we compute the K→π semi-leptonic form factors in the range of momentum transfers $0\lesssim q^{2}\leq q^{2}_{\max}=(m_{K}-m_{\pi})^{2}$ in lattice QCD with N _f =2+1 dynamical flavours. In this way we are able to determine $f_{+}^{K\pi}(0)$ without any interpolation in the momentum transfer, thus eliminating one source of systematic error. This study confirms our earlier phenomenological ansatz for the strange quark mass dependence of the scalar form factor. We identify and estimate potentially significant NNLO effects in the chiral expansion that guides the extrapolation of the data to the physical point. Our main result is $f_{+}^{K\pi}(0)=0.9599(34)(^{+31}_{-47})(14)$ , where the first error is statistical, the second error is due to the uncertainties in the chiral extrapolation of the lattice data and the last error is an estimate of potential discretisation effects.     

B → X_sγ in BLMSSM

Applying the effective Lagrangian method,we study the flavor changing neutral current process b→ sγwithin the minimal supersymmetric extension of the Standard Model,where baryon and lepton numbers are local gauge symmetries.Constraints on the parameters are investigated numerically with the experimental data for the branching ratio of B→ X_sγ.Additionally,we present the corrections to direct CP-violation in B→ X_sγ and time-dependent CP-asymmetry in B→K~*γ.With appropriate assumptions on the parameters,we find the direct CP-violation Acp is very small,while one-loop contributions to S_(K~*_γ) can be significant.     

Polarization phenomena in NN ↔ Dπ reactions

On the basis of a relativistic approach, NN ? Dπ reactions are analyzed in detail. The coherent sum of one-nucleon-exchange and pion-rescattering diagrams is calculated. It is shown that polarization observables are highly sensitive to off-mass-shell effects within the deuteron and that some of these observables can change sign upon taking these effects into account. The effect of the deuteron P wave is also investigated. The results obtained by calculating a full set of observables are compared with experimental data on the reaction pp → Dπ ⁺.     

On scalar resonances in ππ→ππ,K\bar K, ηη reactions

Carried out is the analysis of the new experimental data on theS-wave of the ππ→ \(K\bar K\) reaction in common with ππ→ππ one in the 1–1.6 Gev energy region. It is shown that new resonances are not required for the explanation of the data and for that the well-knownS ^* (980) and ε (1300–1400) resonances and their mixing only are enough. Once more confirmed is the possibility forS ^* (980) to be the \(qq\bar q\bar q\) from (9,0⁺) nonet of the \(qq\bar q\bar q\) mesons predicted by the MIT-bag model. Moreover, it is shown that the ε(1300–1400) resonance can be interpreted as a member of the second four-quark (9,0⁺)-nonet. We predict the bright manifestation of theS ^* and ε-resonances in the π⁺π^? →ηη reaction. The analysis of the data shows that the ε-meson cannot be a pureSU (3)-singlet and therefore it cannot pretend to the role of the gluonium. Discussed is critically the Törnqvist's analysis for scalar mesons.     

Studying the ω mass in-medium in γ + A →π0γ + X reactions

Simulations based on a coupled-channel transport model have been performed to analyze the feasibility to study the in-medium ω mass exploiting the process γ + A→π⁰γ + X for C, Ca and Nb nuclei. The distortions due to final-state interactions of the π⁰ and background contributions from the reaction γ + A→π⁰π⁰ + X are found to be small in the mass range of interest ( 0.6 < M _π0γ < 0.8 GeV). Furthermore, the effect of the detector resolution on the π⁰γ mass determination is discussed. Received: 5 December 2000 / Accepted: 18 May 2001     

The K * Kπ and ρππ couplings in QCD

The light cone QCD sum rules are derived for the K ^* Kπ coupling g _K ^* Kπ and the ρππ coupling g _ρππ. The contribution from the excited states and the continuum is subtracted cleanly through the double Borel transform with respect to the two external momenta, p ₁ ², p ₂ ²= (p−q)². Our result g _K ^* Kπ= (8.7 ± 0.5) and g _ρππ= (11.5 ± 0.8) is in good agreement with the experimental value. Received: 31 July 1998 / Revised version: 20 November 1998     

Non-perturbative chiral approach to K−p → γY reactions

A recently developed non-perturbative chiral approach to describe the S = −1 meson-baryon reactions has been extended to investigate the near threshold K⁻p → γΛ,γΣ⁰ reactions. With the parameters governed by chiral SU(3) symmetry, we show that the predicted branching ratios Γ_K⁻p→γΛ/Γ_K⁻p→all and Γ_{K⁻p→γΣ⁰}/Γ_K⁻p→all are close to the experimental values. The coupling with the η channels, which was shown to be important in the S = −1 meson-baryon reactions, is also found to be significant here. Our results are consistent with the interpretation of the Λ(1405) as a quasi-bound meson-baryon state as found in other similar chiral approaches.