A new experimental limit for the decay K+ → π+γγ

A search for K⁺ → π⁺γ, π⁺γγ, π⁺γγγ was made detecting pions from stopped kaons in the kinetic energy region between 117 MeV and 127 MeV. New Limits of 1.4 ×10^?6, 8.4 × 10^?6 and 1.0 × 10^?4 for the branching ratio were obtained assuming a phase-space spectrum on the pion energy. The first limit also aplies to another process K⁺ → π⁺ + a, where a is a light meson with mass smaller than 100 MeV/c² and decays into nγ's with lifetime less than 10^?9 s.     

Laser spectroscopic study of multiple Eu3+ sites and their crystal fields in YAlG crystals

Resonance fluorescence spectra are excited from a single crystal of curopium doped yttrium aluminum garnet. An analysis from the energy spectrum shows that the spectra are due to trivalent europuim ions occupying two different sites in the unit cell and a crystal field analysis reveals that these ions at these sites experience fields of orthorhombic and axial symmetry. The former is that expected if Eu³⁺ replaces the Y³⁺ at the orthorhombic d sites, the latter if the lanthanide ion replaces the Al³⁺ ions at the a sites (with a distorted C_3i symmetry), there are indications that Eu³⁺ prefers the a over the d sites.     

Study of decay mechanisms in B--->Lambdac+ppi- decays and observation of low-mass structure in the Lambdac+p system

Using a sample of 152 x 10(6) BB pairs accumulated with the Belle detector at the KEKB e+e- collider, we study the decay mechanism of three-body charmed decay B- --> Lambdac+ ppi-. The intermediate two-body decay B--->Sigmac (2455)0 p is observed for the first time with a branching fraction of (3.7 +/- 0.7 +/- 0.4 +/- 1.0) x 10(-5) and a statistical significance of 8.4sigma. We also observe a low-mass enhancement in the (Lambdac+p) system, which can be parametrized as a Breit-Wigner function with a mass of (3.35(-0.02)(+0.01) +/-0.02) GeV/c2 and a width of (0.07(-0.03)(+0.04) +/-0.04) GeV/c2. We measure its branching fraction to be (3.9(-0.7)(+0.8) +/- 0.4 +/- 1.0) x 10(-5) with a statistical significance of 6.2sigma. The errors are statistical, systematic, and that of the Lambdac+-->pK- pi+ decay branching fraction.     

Effect of the vortices on the nuclear spin relaxation rate in the unconventional pairing states of the organic superconductor (TMTSF)2PF6

This Letter theoretically discusses quasiparticle states and nuclear spin relaxation rates T1-1 in the quasi-one-dimensional superconductor (TMTSF)2PF6 under a magnetic field applied parallel to the conduction chains. We study the effects of Josephson-type vortices on T1(-1) by solving the Bogoliubov-de Gennes equation for p-, d- or f-wave pairing interactions. In the presence of line nodes in pairing functions, T1(-1) is proportional to T in sufficiently low temperatures because quasiparticles induced by vortices at the Fermi energy relax spins. We also try to identify the pairing symmetry of (TMTSF)2PF6.     

SSD1, which encodes a plant-specific novel protein,controls plant elongation by regulating cell division in rice

Plant height is one of the most important traits in crop improvement. Therefore revealing the mechanism of plant elongation and controlling plant height in accordance with breeding object is important. In this study we analyzed a novel dwarf mutant, ssd1, of which phenotype is different from typical GA- or BR-related dwarf phenotype. ssd1 exhibits pleiotropic defects in elongation of various organs such as stems, roots, leaves, and flowers. ssd1 also shows abnormal cell files and shapes, which suggests defects of normal cell division in the mutant. Map-based cloning and complementation test demonstrated that the dwarf phenotype in ssd1 mutant was caused by insertion of retrotransposon in a gene, which encodes plant-specific protein with unknown biochemical function. A BLAST search revealed that SSD1-like genes exist in diverse plant species, including monocots and dicots, but not fern and moss. Our results demonstrate that SSD1 controls plant elongation by controlling cell division in higher plants.     

Improved constraints on D0-D0 mixing in D0 --> K+ pi- decays from the Belle detector

We report the results of a search for D0-D0 mixing in D0 --> K+ pi- decays based on 400 fb(-1) of data accumulated by the Belle detector at KEKB. Both assuming CP conservation and allowing for CP violation, we fit the decay-time distribution for the mixing parameters x and y, as well as for the parameter R(D), the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays. The 95% confidence level region in the (x'2,y') plane is obtained using a frequentist method. Assuming CP conservation, we find x'2 < 0.72 x 10(-3) and -9.9 x 10(-3) < y' < 6.8 x 10(-3) at the 95% confidence level; these are the most stringent constraints on the mixing parameters to date. The no-mixing point (0,0) has a confidence level of 3.9%. Assuming no mixing, we measure R(D) = (0.377 +/- 0.008 +/- 0.005)%.     

Structure and mechanical properties of nylon 6.12 prepared by temperature slope crystallization. I. Crystallization of oriented spherulitic textures

Oriented spherulitic textures of a rod-shaped nylon 6.12 sample were crystallized by the temperature slope method. Crystallization conditions were compared by changing temperatures and growth rates. Three types of textures (negative spherulites, positive spherulites, and spherulitic aggregates) were observed by this method. The negative textures appeared when the growth rate was less than 0.1 mm/h. Crystalline orientation and mechanical properties of the textures were investigated by x-ray diffraction and micro-hardness measurements, respectively. The hydrogen-bonded (010) planes were perpendicular to the growth direction in the negative spherulite, while they were parallel to the growth direction in the positive spherulite. In the spherulitic aggregates, the b axis was parallel to the growth direction, while the (010) planes formed roughly an angle of 45° with the growth direction. Due to the orientation of the hydrogen-boned planes, the negative texture exhibited an anisotropy, with hardness values of 106 MPa and 137 Mpa when measured perpendicular or parallel to the growth direction, respectively.     

Extended string field theory for massless higher-spin fields

We propose a new gauge field theory which is an extension of ordinary string field theory by assembling multiple state spaces of the bosonic string. The theory includes higher-spin fields in its massless spectrum together with the infinite tower of massive fields. From the theory, we can easily extract the minimal gauge-invariant quadratic action for tensor fields with any symmetry. As examples, we explicitly derive the gauge-invariant actions for some simple mixed symmetric tensor fields. We also construct covariantly gauge-fixed action by extending the method developed for string field theory.     

Laser Light and X-Ray Diffraction Studies of Oriented Isotactic Polypropylene (iPP) Prepared by Temperature Slope Crystallization

Isotactic polypropylene (iPP) film was melt-crystallized in a temperature gradient. The iPP film showed well oriented α- and β-crystalline textures along the gradient. The crystalline structure, phase transition boundary and lamellar twisting were examined by X-ray diffraction and laser light diffraction (LLD). On the α-β boundary, LLD shows a sharp streak perpendicular to the boundary, where the a-axis of the β-crystal is oriented perpendicular to the temperature gradient. Apart from the boundary, the a-axis of the β-crystal becomes parallel to the gradient. The β-crystal shows lamellar twisting with a pitch of 200 μm at room temperature. When heated the β-crystal, the lamellar distance of 295Å at room temperature decreases to 285Å at 80–100°C and then increases to more than 300Å above 120°C. During the heating, the value of the twist period increases from 200 to 210 μm at 90–100°C, and then to above 224 μm at 140°C. The increase of the twist period is related to the increasing crystalline thickness of the β-lamellae.