Differential cross sections for np and nd elastic scattering near 130 MeV

We have measured the np (nd) elastic scattering cross sections at 25(17) angles in the interval 30°–168° (c.m.), using a neutron beam with a broad spectrum peaked near 130 MeV. At backward angles the outgoing charged particles from a liquid hydrogen (deuterium) target were detected; at forward angles we detected neutrons scattered from a hydrogenated (deuterated) scintillating target. Cross sections have been normalized to the energy dependent solution of the Livermore nucleon-nucleon partial wave analysis, evaluated at 130 MeV. The np measurements represent a marginal improvement on previous work; the nd cross sections show some differences from pd measurements, in agreement with earlier indications at an energy of 152 MeV.     

On Dumont's polynomials

We derive two generating functions and an explicit formula for the polynomials {H_n(x)} studied by Dumont.     

Specific heat of A-15 Nb3Al0.83Ge0.21

The specific heat of A-15 Nb₃Al_.83Ge_.21 with a transition temperature, T_c, of 20.0 K has been measured from 6 to 25 K. Values of the parameters derived from the data are γ=35.0±2 mJ/mole-K²; the Debye temperature, θ_D=278±5 K; the energy gap, △, normalized as 2△/kT_c, is 4.9±.3, and the thermodynamic critical field, H_c(0), is 4700±300 Gauss.     

Spin correlations in the paramagnetic phase and ring exchange in La2CuO4

Spin correlations in the paramagnetic phase of La(2)CuO(4) have been studied using polarized neutron scattering, with two important results. First, the temperature dependence of the characteristic energy scale of the fluctuations and the amplitude of the neutron structure factor are shown to be in quantitative agreement with the predictions of the quantum nonlinear sigma model. Second, a comparison of a high-temperature series expansion of the equal-time spin correlations with the diffuse neutron intensity provides definitive experimental evidence for ring exchange.     

Precision model independent determination of |Vub| from B --> pilnu

A precision method for determining |V(ub)| using the full range in q(2) of B --> pilnu data is presented. At large q(2) the form factor is taken from unquenched lattice QCD, at q(2) = 0 we impose a model independent constraint obtained from B --> pipi using the soft-collinear effective theory, and the shape is constrained using QCD dispersion relations. We find |V(ub)| = (3.54 +/- 0.170 +/- 0.44) x 10(-3). With 5% experimental error and 12% theory error, this is competitive with inclusive methods. Theory error is dominated by the input points, with negligible uncertainty from the dispersion relations.     

Grüneisen ratio divergence at the quantum critical point in CeCu(6-x)Agx

The heavy-fermion system CeCu6-xAgx is studied at its antiferromagnetic quantum critical point, xc=0.2, by low-temperature (T> or =50 mK) specific heat, C(T), and volume thermal expansion, beta(T), measurements. Whereas C/T proportional to log((T0/T) would be compatible with the predictions of the itinerant spin-density-wave (SDW) theory for two-dimensional critical spin fluctuations, beta(T)/T and the Grüneisen ratio, Gamma(T) proportional to beta/C, diverge much weaker than expected, in strong contrast to this model. Both C and beta, plotted as a function of the reduced temperature t=T/T0 with T0=4.6 K, are similar to what was observed for YbRh2(Si(0.95)Ge(0.05))2 (T0=23.3 K), indicating a striking discrepancy to the SDW prediction in both systems.     

Microscopic phenomena found within enclosed surface laser ablation of 20 nm thick aluminium films

This paper investigates the microscopic features which occur when a four-layered film is ablated using Q-switched Nd:YAG laser. The four-layered films consist of a vacuum-deposited aluminium layer (0.02 μm) upon an oriented polypropylene (OPP) film (30 μm) which has been laminated using an inert adhesive and a second OPP film. Laser radiation is absorbed principally by the aluminium layer, melting and/or vaporising it. Upon cooling, the aluminium layer is rearranged into discrete microscopic particles, which give laser-treated areas of the film a transparent appearance. Within the films are found microscopic features, which can be divided into three distinct types: aluminium demetallisation features, polymer distortion features and particle features. Features from each of these categories can exist within a single laser track depending upon the laser parameters used for transparentisation.     

Micromachined array tip for multifocus fiber-based optical coherence tomography

High-resolution optical coherence tomography demands a large detector bandwidth and a high numerical aperture for real-time imaging, which is difficult to achieve over a large imaging depth. To resolve these conflicting requirements we propose a novel multifocus fiber-based optical coherence tomography system with a micromachined array tip. We demonstrate the fabrication of a prototype four-channel tip that maintains a 9-14-microm spot diameter with more than 500 microm of imaging depth. Images of a resolution target and a human tooth were obtained with this tip by use of a four-channel cascaded Michelson fiber-optic interferometer, scanned simultaneously at 8 kHz with geometric power distribution across the four channels.