Scalar mesons in ππ and K¯K scattering

The s-wave pion scattering amplitude is analysed with the aim to clarify the mass spectrum of scalar mesons and to find evidence of lightest glueball. The S-matrix and K¯K coupled channel formalism is used. The existence of scalar mesons S^* and is implied by the data. The production K¯K and the elastic K¯KK¯K coupled amplitudes are predicted from the scattering data. The couplings c f S^* to and K¯K states are determined.     

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     

Instantons and Kähler manifolds

It is shown that for two-dimensional Euclidean chiral models of the field theory with values in arbitrary Kähler manifold duality equations reduce to the Cauchy-Riemann equations on this manifold. A class of models is described possessing such type solutions, the so called instanton solutions.     

Flavor annihilation and the decaysD s →K 0 * K

We have studied \(D_s^ + \to K_0^{* + } \bar K^0\) and \(D_s^ + \to \bar K_0^{*0} K^ +\) decays in the factorization of the hadron currents approximation. The spectator model leads the decays have different but negligible branching ratios. We show, however, that the inclusion of annihilation contribution can enhance the branching ratios. We predict that \(B(D_s^ + \to \bar K_0^{*0} K^ + )\) and \(B(D_s^ + \to K_0^{* + } \bar K^0 )\) could be around 2%.     

K→ππγ and chiral perturbation theory

Weak radiative decaysK _L,S →π⁺π^?γ andK ⁺→π⁺π⁰γ are reexamined. The electromagnetic form factors and long-distance contributions to the direct photon emission are evaluated using the higher order effective chiral Lagrangian. We find that (1) the naive soft-pion theorem cannot be applied to the magnetic-type transition amplitude, (2) the shortdistance contribution toK _L →π⁺π^?γ is comparable to or even bigger than the long-distance one, (3) the ΔI=1/2 enhancement persists in the decayK ⁺→π⁺π⁰γ, (4) to the order of 1/Λ _χ ² (Λ _χ being the chiral-symmetry breaking scale) the direct photon emission amplitude does not receive a contribution from penguin operators, and (5) the 1/N _c expansion improves the discrepancy between theory and experiment.     

Nonfactorization and color-suppressedB →ψ(ψ′)+K(K*) decays

Using a value ofa ₂=0.1±0.03 in a formalism which usesN _c =3, we show that one can define an effectivea ₂, which includes the contribution of nonfactorized effects, for color-suppressed decayB→ψK. We determine the magnitude of this effectivea ₂, which is process-dependent and, in general, complex, in certain commonly used models of form factors. We analyze the color-suppressedB→ψK* branching ratio and longitudinal polarization and demonstrate that nonfactorization effects are needed to understand these data in certain commonly used models of form factors. We extend the analysis to color-suppressed decayB→ψ′K*, whereψ′=ψ(2S), and color-favored decay $\bar B^0 \to D^{* + } \rho ^ - $ where we demonstrate that factorization scheme works well.     

Hypernuclear production induced by in-flight K and π

The development in treating K- and -induced hypernuclear production reactions is reviewed, including the application of DWIA to the (K^–, K⁺) reaction to produce ^–. After summarizing the conventional DWIA treatment without spin-dependence, we discuss the calculational method of strength functions up to the continuum. Finally the process is reformulated starting from the elementary amplitudes with the spin-flip component as well as the spin-nonflip one. The new treatment is shown to be powerful and the emphasis is put on the production of polarized hypernuclei, which provides a useful spectroscopic tool for the weak-decay mechanism.Dedicated to our distinguished collaborator, Professor Jan ofka (1943–1991), to the memory of his inspiration in hypernuclear physics and his wide, friendly activities in our community.The authors are very grateful to the late Professor Jan ofka who was a distinguished collaborator for a long time. He coordinated many collaborations between e and Japan. We will miss his scientific and organizational activities in hypernuclear physics. The authors express their thanks to O. Richter, M. Sotona, R. Wünsch, H. Ejiri and T. Kishimoto for collaboration and discussion on several parts of the calculated results. This work has been supported by the Grant-in-Aid for Scientific Research (C) and also by A Grant under The Monbusho International Scientific Research program (Joint Research 1990–1991).     

Interferometric measurements of the dipole polarizability α of molecules between 300 K and 1100 K

The temperature dependence of the dipole polarizability α(λ, T) of free atoms and molecules is determined by precise measurements of the refractive index n of gases in the extended temperature range between 300 K and 1100 K for wavelength λ = 632·99 nm, using a specially constructed Michelson twin interferometer. α of the noble gases is observed to be independent of T. α of the molecular gases H₂, N₂, O₂, and CH₄ increases with increasing temperature by an amount of approximately 1 per cent per 1000 K. These results are in excellent agreement with theoretical predictions. They will be compared to previously measured temperature dependent polarizabilities.     

The Sasaki join and admissible Kähler constructions

We give a survey of our recent work (Boyer and Tønnesen-Friedman (2013) [50], [51], [30], Boyer and Tønnesen-Friedman (2014) [33], [29], [36]) describing a method which combines the Sasaki join construction of Boyer et al. (2007) [31] with the admissible Kähler construction of Apostolov et al. (2006, 2004, 2008) [26], [27], [14], [25] to obtain new extremal and new constant scalar curvature Sasaki metrics, including Sasaki–Einstein metrics. The constant scalar curvature Sasaki metrics also provide explicit solutions to the CR Yamabe problem. In this regard we give examples of the lack of uniqueness when the Yamabe invariant $\lambda \left(M\right)$ is positive.