Modulation efficiency of LiNbO₃ waveguide electro-optic intensity modulator operating at high microwave frequency

The modulation efficiency, at high-frequency microwave modulation, of a LiNbO3 waveguide electro-optic modulator is shown to be degraded severely, especially when it is used as a frequency translator in a Brillouin-distributed fiber-sensing system. We derive an analytical expression for this attenuation regarding the phase-velocity mismatch and the impedance mismatch during the modulation process. Theoretical results are confirmed by experimental results based on a 15 Gb/s LiNbO3 optical intensity modulator

Is the f0(600)f_0(600) meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond

O(N) linear $\sigma$ model is solvable in the large $N$ limit and hence provides a useful theoretical laboratory to test various unitarization approximations. We find that the large $N_c$ limit and the $m_\sigma\to \infty$ limit do not commute. In order to get the correct large $N_c$ spectrum one has to firstly take the large $N_c$ limit. We argue that the $f_0(600)$ meson may not be described as generated dynamically. On the contrary, it is most appropriately described at the same level as the pions, i.e, both appear explicitly in the effective lagrangian. Actually it is very likely the $\sigma$ meson responsible for the spontaneous chiral symmetry breaking in a lagrangian with linearly realized chiral symmetry.Comment: 15 pages, 3 figurs; references added; discussions slightly modified; revised version accepted by IJMP

Highlights of the TEXONO Research Program on Neutrino and Astroparticle Physics

This article reviews the research program and efforts for the TEXONO Collaboration on neutrino and astro-particle physics. The ``flagship'' program is on reactor-based neutrino physics at the Kuo-Sheng (KS) Power Plant in Taiwan. A limit on the neutrino magnetic moment of \munuebar < 1.3 X 10^{-10} \mub} at 90% confidence level was derived from measurements with a high purity germanium detector. Other physics topics at KS, as well as the various R&D program, are discussedComment: 10 pages, 9 figures, Proceedings of the International Symposium on Neutrino and Dark Matter in Nuclear Physics (NDM03), Nara, Japan, June 9-14, 200

On the nature of the lightest scalar resonances

We briefly review the recent progresses in the new unitarization approach being developed by us. Especially we discuss the large $N_c$ $\pi\pi$ scatterings by making use of the partial wave $S$ matrix parametrization form. We find that the $\sigma$ pole may move to the negative real axis on the second sheet of the complex $s$ plane, therefore it raises the interesting question that this `$\sigma$' pole may be related to the $\sigma$ in the linear $\sigma$ model.Comment: Talk presented by Zheng at ``Quark Confinement and Hadron Spectroscopy VI'', 21--25 Sept. 2004, Cagliari, Italy. 3 pages with 2 figure