Improved direct measurement of A(b) and A(c) at the Z(0) pole using a lepton tag

The parity violation parameters A(b) and A(c) of the Zb(b) and Zc(c) couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the Z(0) pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-1998 SLD sample of 550,000 Z(0) decays produced with highly polarized electron beams, we measure A(b) = 0.919+/-0.030(stat)+/-0.024(syst), and A(c) = 0.583+/-0.055(stat)+/-0.055(syst).     

Study of B0 --> J/psiK(*)0pi(+)pi(-) decays with the collider detector at Fermilab

We report a study of the decays B0 --> J/psiK(*)0pi(+)pi(-), which involve the creation of a uu or dd quark pair in addition to a b -->c(cs) decay. The data sample consists of 110 pb(-1) of pp collisions at square root[s] = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995. We measure the branching fractions to be B(B0 --> J/psiK(*0)pi(+)pi(-)) = (6.6 +/- 1.9 +/- 1.1)x10(-4) and B(B0 --> J/psiK0pi(+)pi(-)) = (10.3 +/- 3.3 +/- 1.5)x10(-4). Evidence is seen for contributions from psi(2S)K(*)0, J/psiK0rho(0), J/psiK(*+)pi(-), and J/psiK1(1270).     

Coherent Hall effect in a semiconductor superlattice

The coherent Hall effect denotes the transient Hall response of impulsively excited coherent charge-carrier wave packets in a solid. We report the first experimental study of this phenomenon (i) using a semiconductor superlattice in crossed electric and magnetic fields as a model for three-dimensional materials and (ii) employing a contactless optoelectronic technique to probe the transient currents. Two field regimes with distinctly different oscillatory wave packet dynamics are found, separated from each other by a transition region where all oscillations are suppressed.     

Surface Enhanced Resonance of Metal Nano Clusters: A Novel Tool for Proteomics

A novel nano-tool based on metal clusters enables the transduction of changes of biorecognitive binding as well as conformation quantitatively into an optical signal which can be observed directly as a color change of a sensor-chip surface.Proteins including various enzymes and serum proteins were spotted via micro-arraying onto the chip surface forming monolayer and thin film dots. Multi-layered (up to 300 nm thick) nano-gel-pads were stabilized by photo crosslinking the protein dots with UV-light. By deposition of metal-nano clusters, synthesized via chemical means or sputter coating on top of photo-crosslinked macromolecules an optical resonance effect was obtained.The response of the novel surface enhanced absorption cluster sensor-chip was transduced spectroscopically in the visible and IR range of the spectrum via an 8 m resolution reflectance scanner.     

Double diffraction dissociation at the Fermilab Tevatron collider

We present results from a measurement of double diffraction dissociation in pp collisions at the Fermilab Tevatron collider. The production cross section for events with a central pseudorapidity gap of width Deltaeta(0)>3 (overlapping eta = 0) is found to be 4.43+/-0.02(stat)+/-1.18(syst) mb [ 3.42+/-0.01(stat)+/-1.09(syst) mb] at square root of (s) = 1800[630] GeV. Our results are compared with previous measurements and with predictions based on Regge theory and factorization.     

Behavior of transversally isotropic cylindrical shells under dynamic application of radial pressure

We consider the problem on the buckling of a transversally isotropic long cylindrical shell under dynamic external pressure. For the cases of a sudden load [1] and a load rapidly increasing with time [2], we compare the results obtained from the two-dimensional Kirchhoff-Love and Timoshenko-Reissner theories.     

High-field EPR studies on polymer film formation from colloidal dispersions

High-field EPR on nitroxide spin probes is applied to characterize the dynamics of small additive molecules and surfactants in polymer films obtained from colloidal dispersions. Due to the increased width of the spectra and the smaller influence of hyperfine-dependent relaxation on the spectral lineshape at W band (94 GHz) compared to X band (9.6 GHz), it is possible to measure subnanosecond rotational correlation times for the isotropic motion of the unpolar spin probe TEMPO in the free volume of poly(acrylate) films. Likewise, the anisotropies of the rotational diffusion tensors of a surfactant and a small ionic additive molecule in poly(fluoroacrylate) films can be determined with better confidence at W band. From these anisotropies it is concluded that the surfactant aggregates exhibit low molecular order, whereas the ionic additives are strongly attached to immobilized ionic clusters. High-field EPR lineshapes at W band are also found to be more sensitive to slow motions on a microsecond time scale than X-band EPR lineshapes. The design of a Fabry-Pérot resonator for measurements on polymer films is discussed and its sensitivity is demonstrated on a wet polymer film with a thickness of 160 μm.     

Fast right-angle spinning EPR on organic radicals: Resolution enhancement and angle determination

Fast right-angle sample spinning (RAS) with rotation frequencies up to 17 kHz at temperatures down to 205 K is applied to electron paramagnetic resonance (EPR) experiments on organic radicals. Echo-detected RAS EPR provides substantial resolution enhancements for the range of anisotropies between 10 and 100 MHz which is not accessible with either magic-angle sample spinning EPR or anisotropy-resolved EPR on the basis of slow rotation. The larger reorientation angles in experiments with fast spinning cause strong phase shifts of the echo, which manifest themselves as regions with negative intensity in the spectrum. These phase shifts and thus the lineshape in echo-detected RAS EPR depend significantly on the relative orientation of theg and hyperfine tensor. For the determination of anisotropies in poorly resolved spectra of organic radicals in disordered solids, we introduce the two-dimensional fixed-angle rotation experiment as an alternative to anisotropy-resolved EPR.     

Potential and limitations of nucleon transfer experiments with radioactive beams at REX-ISOLDE

As a tool for studying the structure of nuclei far off stability the technique of γ-ray spectroscopy after low-energy single-nucleon transfer reactions with radioactive nuclear beams in inverse kinematics was investigated. Modules of the MINIBALL germanium array and a thin position-sensitive parallel plate avalanche counter (PPAC) to be employed in future experiments at REX-ISOLDE were used in a test experiment performed with a stable ³⁶S beam on deuteron and ⁹Be targets. It is demonstrated that the Doppler broadening of γ lines detected by the MINIBALL modules is considerably reduced by exploiting their segmentation, and that for beam intensities up to 10⁶ particles/s the PPAC positioned around zero degrees with respect to the beam axis allows not only to significantly reduce the γ background by requiring coincidences with the transfer products but also to control the beam and its intensity by single particle counting. The predicted large neutron pickup cross-sections of neutron-rich light nuclei on ²H and ⁹Be targets at REX-ISOLDE energies of 2.2 MeV ^. A are confirmed. Received: 9 October 2000 / Accepted: 28 January 2001