Search for CP violation in τ±→K(S)0π±ντ decays at Belle

We report on a search for CP violation in τ(±)→K(S)(0)π(±)ν(τ) decays using a data sample of 699 fb(-1) collected by the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K(S)(0)π(±) system and found to be compatible with zero with a precision of O(10(-3)) in each mass bin. Limits for the CP violation parameter Im(η(S)) are given at the 90% confidence level. These limits are |Im(η(S))| < 0.026 or better, depending on the parametrization used to describe the hadronic form factors, and improve upon previous limits by 1 order of magnitude.     

Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.     

Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2−x Ce x Cu3O10+δ system

We have investigated the superconducting properties of the Bi_1.7 Pb_0.3Sr₂Ca_2−xCe _x Cu₃O_10+δ system with x=0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the c-parameter with increased substitution of Ce at Ca site and volume fraction of high T _c (2 : 2 : 2 : 3) phase decreases and low T _c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for x=0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca²⁺ → Ce⁴⁺ replacement changes the hole carrier concentration. Hole filling is the cause of lowering T _c of the system.     

On optimal control problems with general boundary conditions

It is shown that the necessary optimality conditions for optimal control problems with terminal constraints and with given initial state allow also to obtain in a straightforward way the necessary optimality conditions for problems involving parameters and general (mixed) boundary conditions. In a similar manner, the corresponding numerical algorithms can be adapted to handle this class of optimal control problems.This research was supported in part by the Commission on International Relations, National Academy of Sciences, under Exchange Visitor Program No. P-1-4174.The author is indebted to the anonymous reviewer bringing to his attention Ref. 9 and making him aware of the possible use of generalized inverse notation when formulating the optimality conditions.     

Measurement of the CP-violation parameter sin2φ1 with a new tagging method at the Υ(5S) resonance

We report a measurement of the CP-violation parameter sin2φ1 at the Υ(5S) resonance using a new tagging method, called "B-π tagging." In Υ(5S) decays containing a neutral B meson, a charged B, and a charged pion, the neutral B is reconstructed in the J/ψK(S)(0) CP-eigenstate decay channel. The initial flavor of the neutral B meson at the moment of the Υ(5S) decay is opposite to that of the charged B and may thus be inferred from the charge of the pion without reconstructing the charged B. From the asymmetry between B-π(+) and B-π(-) tagged J/ψK(S)(0) yields, we determine sin2φ1=0.57±0.58(stat)±0.06(syst). The results are based on 121 fb(-1) of data recorded by the Belle detector at the KEKB e(+)e(-) collider.     

Estimation of the characteristic ratio of poly[2-(triphenylmethoxy)ethyl methacrylate] from hydrodynamic properties of its dilute solutions

Properties of poly[2-(triphenylmethoxy)ethyl methacrylate] (PTEMA) molecules in solutions (under O-conditions and in “good” solvents) were investigated by the light scattering, sedimentation, viscometric and by phase equilibria methods. The O-temperature (47°) was determined for the system mesitylene-PTEMA. Unusual correlations of hydrodynamic data with molecular weight are discussed and slight branching of polymer chains is accepted as a probable explanation. Data for mesitylene solutions under O-conditions are used to estimate the characteristic ratio of PTEMA molecules ($\text{R}{}_0{}^2\text{/nl}{}^2\text{= 19}$).     

Determination of small amounts of tungsten by atomic absorption spectrometry after extraction separation

Small amounts of tungsten can be determined by atomic absorption spectrometry, after reduction with tin(II) and separation of the thiocyanate complex into methyl isobutyl ketone. The organic phase is aspirated into an acetylene-nitrous oxide flame There are no interferences from 1000-fold amounts of Zr or Cr(III), 200-fold amounts of U or Ti. 100-fold V or 10-fold Mo. Interference from large amounts of iron(III) is avoided by prior reduction. The method was successfully applied to the determination of tungsten in steels and zirconium alloys.     

Electrometric titrations of Bi(III), Cu(II), Pt(IV), Te(VI) and Te(IV) with standard iron(II) solution in alkaline medla containing hexitols

Potentiometric, bipotentiometric and biamperometric titrations with an iron(II) salt in alkaline solutions containing sorbitol are reported. Suitable conditions are discussed for determinations based on the Bi(III) → Bi°, Cu(II) → Cu(I) → Cu°, Pt(IV) → Pt(II) → Pt° and Te(VI) → Te(IV) → Te° → telluride systems.