Updated post-WMAP benchmarks for supersymmetry

We update a previously-proposed set of supersymmetric benchmark scenarios, taking into account the precise constraints on the cold dark matter density obtained by combining WMAP and other cosmological data, as well as the LEP and constraints. We assume that R parity is conserved and work within the constrained MSSM (CMSSM) with universal soft supersymmetry-breaking scalar and gaugino masses m₀ and m_1/2. In most cases, the relic density calculated for the previous benchmarks may be brought within the WMAP range by reducing slightly m₀, but in two cases more substantial changes in m₀ and m_1/2 are made. Since the WMAP constraint reduces the effective dimensionality of the CMSSM parameter space, one may study phenomenology along WMAP lines in the (m_1/2, m₀) plane that have acceptable amounts of dark matter. We discuss the production, decays and detectability of sparticles along these lines, at the LHC and at linear e ⁺ e^- colliders in the sub- and multi-TeV ranges, stressing the complementarity of hadron and lepton colliders, and with particular emphasis on the neutralino sector. Finally, we preview the accuracy with which one might be able to predict the density of supersymmetric cold dark matter using collider measurements.Received: 2 September 2003, Published online: 4 February 2004     

Search for lepton-flavor and lepton-number violation in the decay tau(-) -->l-(+)h+(-)h'(-)

A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons is performed using 221.4 fb(-1) of data collected at an e+e- center-of-mass energy of 10.58 GeV with the BABAR detector at the SLAC PEP-II storage ring. In all 14 decay modes considered, the observed data are compatible with background expectations, and upper limits are set in the range B(tau-->lhh')<(0.7 - 4.8) x 10(-7) at 90% confidence level.     

Synthesis of optically active constrained 2-substituted norstatines: a straightforward application of Seebach's "SRS" synthetic principle

A straightforward two-step methodology of synthesis of optically active (2R)-substituted norstatines via addition of N-tert-butoxycarbonyl-substituted aldimines to (2S)-chiral enolates of 1,3-dioxolan-4-ones has been developed. In particular, the use of the natural (2S)-malic acid is examined for the synthesis of potential GABAergic spirocyclic gamma-lactams.     

Symmetry of three-center,four-electron bonds

Three-center, four-electron bonds provide unusually strong interactions; however, their nature remains ununderstood. Investigations of the strength, symmetry and the covalent versus electrostatic character of three-center hydrogen bonds have vastly contributed to the understanding of chemical bonding, whereas the assessments of the analogous three-center halogen, chalcogen, tetrel and metallic -type long bonding are still lagging behind. Herein, we disclose the X-ray crystallographic, NMR spectroscopic and computational investigation of three-center, four-electron [D–X–D]⁺ bonding for a variety of cations (X⁺ = H⁺, Li⁺, Na⁺, F⁺, Cl⁺, Br⁺, I⁺, Ag⁺ and Au⁺) using a benchmark bidentate model system. Formation of a three-center bond, [D–X–D]⁺ is accompanied by an at least 30% shortening of the D–X bonds. We introduce a numerical index that correlates symmetry to the ionic size and the electron affinity of the central cation, X⁺. Providing an improved understanding of the fundamental factors determining bond symmetry on a comprehensive level is expected to facilitate future developments and applications of secondary bonding and hypervalent chemistry.

The factors determining the symmetry and the fundamental nature of the three-center, four-electron bonds are assessed.     

Modélisation du comportement thermique d'un outil de fraisage : approche par identification de système non entierThermal modelling of a milling tool: a noninteger system identification approach

In this work we present an experimental apparatus devoted to the thermal characterisation of a milling tool. The experimental device used thermistors, one for each insert. Each thermistor is located at a point in the tool close to the tip of the insert. The heat flux in each insert is expressed according to the temperature at the sensor from a non-integer model. The parameters of the model are identified from transient evolutions measurements of the temperature on the sensor and on the cutting edge. An application shows the difference in the behaviour of each insert during machining from the estimated heat fluxes. To cite this article: J.-L. Battaglia et al., C. R. Mecanique 330 (2002) 857–864.     

SULPHUR CONTAINING HETERODIPOLAROPHILES. VARIABLE STEREOCHEMISTRY OF THE CYCLOADDITION OF THIOBENZOPHENONES TO KETENIMINES

Abstract

The thermal cycloaddition between thiobenzophenones (1) and ketenimines (2) takes place according to two reaction modes, the stereochemical course being determined by the type of substituent at nitrogen on the cumulene. Specifically, N-arylketenimines (2a) (X = H) react with (1) as a formal 4π system giving as final products 4H-3,1-benzothiazines (3) (1,4-cyclisation), whereas N-aryl ortho-disubstituted compounds (2b) (X = Me), as well as N-alkyl derivatives (2c), behave as 2π component to give 2-iminothietans (4) (1,2-cyclisation) (Scheme I). In the formation of the six membered ring compound (3), the ketenimine (2a) can be viewed to act as a 1,4-heterodiene to give the intermediate (3a) by addition of (1) across the C[dbnd]N bond and the C[dbnd]C of the N-aryl ring. Both reactions proved to be stereoselective.     

Exciton condensation driving the periodic lattice distortion of 1T-TiSe2

We address the lattice deformation of 1T-TiSe2 within the exciton condensate phase. We show that, at low temperature, condensed excitons influence the lattice through electron-phonon interaction. It is found that at zero temperature, in the exciton condensate phase of 1T-TiSe2, this exciton condensate exerts a force on the lattice generating ionic displacements comparable in amplitude to what is measured in experiment. This is thus the first quantitative estimation of the amplitude of the periodic lattice distortion observed in 1T-TiSe2 as a consequence of the exciton condensate phase.     

Structural properties of some heteroaryl amines. Crystallographic studies on 2-N-(2,4,6-trinitrophenyl)-pyridineamine(I),-4-methylthiazoleamine(II), and-pyrimidineamine(III)

Crystallographic properties of the title compounds are reported and inter- and intra-molecular interactions of the amino group are discussed and related to spectroscopic data. The geometry of the nitrogroups and of the 2-aminoheterocyclic moiety indicate that classical conjugation theory cannot explain the UV/vis spectra. The red shift observed on substituting H by a Me on the 2-amino group is interpreted in terms of internal charge-transfer.     

Vibrationally inelastic scattering and relaxation times in gaseous HF

A numerical fit to computed ab initio points of the HF–HF potential energy surface is here employed in its simplest spherical form to solve the corresponding close-coupling equations that yield vibrationally inelastic collision cross sections for the V/T process in the gas phase. The existence of a deep potential well in the interaction is examined here for its effect on near-threshold cross section behavior and evidence is found, through the present calculations, for the relative importance of several (orbiting) shape resonances that contribute to the Q_1←0 cross sections at low collision energies (≤0.4 eV). The bearing of such lengthened interaction times on the corresponding low temperature relaxation times is shown in the ensuing calculation of pτ in the T range between 300 and 4000 K. In spite of the simplicity of the present model, quite good agreement is in fact found with experiments in the low- T region, while the lack of V, R/T coupling explains the departure of the computed pτ, above 1000 K, from the experimental findings.