TeV-scale Type-II Seesaw Models and Possible Collider Signatures

A natural extension of the standard model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a 6 \times6 neutrino mass matrix. We show that three light Majorana neutrinos (i.e., the mass eigenstates of \nu_e, \nu_\mu and \nu_\tau) are exactly massless, if and only if M_L = M_D M^{-1}_R M^T_D exactly holds in this seesaw model. We propose three simple Type-II seesaw scenarios with broken A_4 \times U(1)_X flavor symmetry to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the 3\times 3 neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.Comment: 4 pages. Talk given by Wei Chao at the 4th International Conference on Flavor Physics, 24-28 September 2007, Beijing (to appear in the proceedings

Modulation instability induced by periodic power variation in soliton fiber ring lasers

Modulation instability with subsideband generation induced by periodic power variation in soliton fiber ring lasers is reported. We found that different wavelength shifts of subsideband generation are related to different periodic power variation. The period of power variation and wavelength shifts of subsideband can be changed by altering the linear cavity phase delay. It is also found that the periodic power variation is caused by the interaction between the nonuniform polarization state of the circulating light and the polarizer in the laser cavity.Comment: 16 pages, 6 figure

Poly[[aqua­tris­(μ-benzene-1,4-dicarboxyl­ato)tricobalt(II)] methanol monosolvate monohydrate]

The asymmetric unit of the title compound, {[Co3(C8H4O4)3(H2O)]·CH3OH·H2O}n, consists of four crystallographically independent Co cations, four benzene-1,4-dicarboxyl­ate (bdc) anions, two water and one methanol solvent mol­ecule. Two of the Co cations and two of the bdc anions are located on centres of inversion, whereas all other atoms are located in general positions. In the crystal, two Co atoms are only fourfold coordinated by three O atoms from three bdc ligands and by one O atom from one coordinated water mol­ecule, while a third Co atom is coordinated by four O atoms from four bdc ligands within a strongly distorted tetra­hedral geometry. The other two Co cations are octa­hedrally coordinated by six O atoms from six bdc anions. The Co cations are linked by the bdc anions into a three-dimensional framework. From this arrangement, cavities are formed in which additional methanol and water mol­ecules are embedded

3-Chloro­pyridin-2-amine

In the title compound, C5H5ClN2, a by-product in the synthesis of ethyl 2-(3-chloro­pyridin-2-yl)-5-oxopyrazolidine-3-carboxyl­ate, the amine groups form inter­molecular hydrogen-bonding associations with pyridine N-atom acceptors, giving centrosymmetric cyclic dimers. Short inter­molecular Cl⋯Cl inter­actions [3.278 (3) Å] also occur