Search for the standard model Higgs Boson in the pp[over]-->ZH-->nunu[over]bb[over] channel

We report a search for the standard model (SM) Higgs boson based on data collected by the D0 experiment at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 260 pb(-1). We study events with missing transverse energy and two acoplanar b jets, which provide sensitivity to the ZH production cross section in the nunu[over]bb[over] channel, and to WH production when the lepton from the W-->lnu decay is undetected. The data are consistent with the SM background expectation, and we set 95% C.L. upper limits on sigma(pp[over]-->ZH/WH)xB(H-->bb[over]) from 3.4/8.3 to 2.5/6.3 pb, for Higgs-boson masses between 105 and 135 GeV.     

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Data on classification of spectra and energy levels of atoms of rare earth elements with unfilled 4f-shells have been collected, systematized and analyzed. A brief account is given of methods for determining transition probabilities and lifetimes of the excited states of atoms and ions. Oscillator strengths for spectral lines of Nd(I), Sm(I), Eu(I), Gd(I), Dy(I), Tm(I) and Yb(I) have been measured using Rojdestvensky's hook method. Lifetimes of some of the excited states of Eu(I), Yb(I) and Yb(II) have been determined by using simultaneously the methods of delayed coincidence, hooks, and total absorption. Our results have been compared with those of other investigators. Atoms with unfilled 4f-shells show some regularities.     

Reaching for [6]n SiC‐cyclacenes and [6]n SiC‐acenes: A DFT approach

Density functional theory (DFT) calculations introduced triplet ground states for [6]_n SiC‐cyclacenes and ‐acenes with alternate silabenzene rings including silicon atoms in 2 opposite edges (n = 6, 8, 10, 12). The singlet‐triplet energy gap (ΔE_(S‐T)), binding energy per atom (BE/n), and NBO calculation with very small band gap (ΔE_LUMO‐HOMO) confirmed the triplet ground states. In contrast to polyacenes, the singlet [6]_n SiC‐cyclacenes displayed more stability improvement than triplets, through n increasing. This may open the way for synthesis of larger stable [6]_n SiC‐cyclacenes. The ΔE_(S‐T), BE/n, and the strain energy through homodesmic equations indicated more stability for larger [6]_n SiC‐cyclacenes, which was more noticeable in singlet states. Cyclacenes and acenes with high conductivity and full point charge were introduced as suitable candidates for hydrogen storage.     

Diastereoselective synthesis of fused [1,3]thiazolo[1,3]oxazins and [1,3]oxazino[2,3-b][1,3]benzothiazoles

An efficient diastereoselective synthesis of 7-ethyl 5,6-dialkyl 7H-[1,3]thiazolo[2,3-b][1,3]oxazin-5,6, 7-tricarboxylates and 2-ethyl 3,4-dialkyl 2H-[1,3]oxazino [2,3-b][1,3]benzothiazole-2,3,4-tricarboxylates via reaction of thiazole and benzothiazole with dialkyl acetylenedicarboxylates in the presence of ethyl pyruvate is described.     

Unsymmetrical dyes derived from 7,8‐dihydrobenzo[c,d]furo[2,3‐f]indole

On the basis of the 7,8‐dihydrobenzo[c,d]furo[2,3‐f]indole nucleus, a number of unsymmetrical carbocyanines as well as styryl dyes have been synthesized and their absorption spectra have been measured. Starting from the deviations of long‐wavelength maxima, the value of electron‐donor ability D has been estimated for the heterocycle under study and a number of dye end groups have been ranked by their electron‐donor properties. Experimental inferences are supported by the quantum chemically calculated bond length alternations and energy levels for the dyes concerned. Copyright © 2009 John Wiley & Sons, Ltd.     

Modulated structure of the superconducting phases in Pb-modified Bi[sbnd]Sr[sbnd]Ca[sbnd]Cu[sbnd]O

Abstract

High resolution electron microscopy has shown that a modulated structure occurs in the Bi[sbnd]Sr[sbnd]Ca[sbnd]Cu[sbnd]O system. Electron diffraction and x-ray diffraction observations show that this modulation produces extra reflections. Diffraction patterns of the Pb-free material have superstructure reflections with wave vectors [0, 1/4.7, 1] and [0, ?1/4.7, 1]. These two waves vectors can generate all of the superstructure relections associated with each fundamental reflection. When PbO is added to the BSCCO system a new wave vector [0. 1/8.5, 0] is introduced. Observations show that within a single grain the two wave vectors coexist for a Pb and Bi ratio of about 0.25. This produces a non-uniform modulated structure which may be due to a superposition of the two wave vectors. The intensity of the [0, 1/4.7, 1] wave vector is substantially reduced in the Pb-modified material. The b' component of both wave vectors in incommensurate with the lattice period. The same superstructures occurs in both the low-T_c phase and the high-T_c phase.     

Study of J/psi-->pp[over],LambdaLambda[over] and observation of eta(c)-->LambdaLambda[over] at Belle

We study the baryonic charmonium decays of B mesons B+-->etacK+ and B+-->J/psiK+, where the etac and J/psi subsequently decay into a pp[over] or LambdaLambda[over] pair. We measure the J/psi-->pp[over] and LambdaLambda[over] anisotropy parameters alphaB=-0.60+/-0.13+/-0.14 (pp[over]), -0.44+/-0.51+/-0.31 (LambdaLambda[over ]) and compare to results from e;{+}e;{-}-->J/psi formation experiments. We also report the first observation of etac-->LambdaLambda[over]. The measured branching fraction is B(etac-->LambdaLambda[over ])=(0.87(+0.24)/(-0.21)(stat)(+0.09/-0.14) (syst)+/-0.27(PDG))x10-3. This study is based on a 357 fb-1 data sample recorded on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider.     

Photoinduced decarboxylation of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid

Photoinduced reactions of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid (SeQCA) were investigated in alkaline media (aqueous NaOH solutions) by electron paramagnetic resonance (EPR) spectroscopy, following the in situ formation of paramagnetic species. According to UV–Vis and nuclear magnetic resonance investigations, protonation (pH ≈ 11) and deprotonation (pH ≈ 13) of the imino hydrogen of the 4‐pyridone moiety has to be considered, reflected also in the different EPR spectra observed upon irradiation. Photoinduced generation of radicals was found only for carboxylate substituted SeQCA; other studied selenadiazoloquinolone derivatives, together with those substituted at the C(8) position (R = H, COOCH₂CH₃, COOCH₃, COCH₃ or CN), did not generate paramagnetic species during exposure. Consequently, photodecarboxylation was suggested as the decisive step, accompanied by the decomposition of the selenadiazole ring, resulting in the formation of ortho‐hydroxylate anions. EPR parameters elucidated from experimental EPR spectra obtained at pH ≈ 11 and pH ≈ 13 indicate the formation of oxygen‐centered radicals at the decarboxylated 4‐pyridone ring. EPR spin trapping experiments with nitromethane confirmed a very effective photoinduced electron transfer from all the selenadiazoloquinolones investigated. Copyright © 2011 John Wiley & Sons, Ltd.     

Electromigration du cuivre de l'argent et de l'or dans l'aluminum

By electromigration experiments we have measured the apparent effective valences of copper, silver and gold in aluminium. These data, used together with complementary calculations, allow us to calculate in each case the cross-terms between ssolute and solvent fluxes. The values thus obtained are qualitatively in good agreement with direct calculations.     

A multi‐addressable molecular switch based on a novel diarylethene with an imidazo [4,5‐f] [1,10] phenanthroline unit

A novel unsymmetrical diarylethene with an imidazo [4,5‐f] [1,10] phenanthroline unit has been synthesized, and its properties including photochromism and fluorescence have been investigated. It showed favorable photochromism and functioned as notable fluorescence switches by photoirradiation in both solution and a poly (methylmethacrylate) film. Moreover, the interaction between the phenanthroline unit of its closed‐ring isomer with trifluoroacetic acid caused a notable change in its absorption, accompanied by an evident color change from magenta to slateblue. Its fluorescence could be modulated by trifluoroacetic acid and triethylamine. By adding enough amount of trifluoroacetic acid in chloroform, its emission peak hypochromatic shifted from 501 nm to 456 nm, and the intensity increased significantly with a concomitant change of color from bright cyan to bright blue. However, its emission intensity decreased notably by 95% with a fluorescence color change from bright cyan to dark gray by the addition of triethylamine. Copyright © 2013 John Wiley & Sons, Ltd.     

Authors' reply

Upper and lower bounds are given for the lowest frequencies of vibration of clamped rhombical plates. These bounds were obtained by using a recently developed method which allows the use of trial functions which do not need to satisfy any boundary conditions.