Exchange and nuclear symmetry interference in He+-He scattering

A method is described to determine the potential difference, V _g-V _u, that will accurately reproduce the exchange and nuclear symmetry oscillations observed by Aberth et al. in their experimental work on He⁺-He differential scattering. It is demonstrated that at higher energies and angles the experimental results for ⁴He⁺-⁴He, ⁴He⁺-³He and ³He⁺-³He appear incompatible with one another when investigated in terms of a two-state scattering theory. This is an indication that at these energies and angles the theory may require modification to include the effects of coupling to higher states.     

The creep behavior of simple structures with a stress range-dependent constitutive model

High temperature design remains an issue for many components in a variety of industries. Although finite element analysis for creep is now an accessible tool, most analyses outside the research domain use long standing and very simple constitutive models—in particular based on a power law representation. However, for many years, it has been known that a range of materials exhibit different behaviors at low and moderate stress levels. Recently, studies of the behavior of high temperature structures with such a stress range-dependent constitutive model have begun to emerge. The aim of this paper is to examine further the detailed behavior of simple structures with a modified power law constitutive model in order to instigate a deeper understanding of such a constitutive model’s effect on stress and deformation and the implications for high temperature design. The structures examined are elementary—a beam in bending and a pressurized thick cylinder—but have long been used to demonstrate the basic characteristics of nonlinear creep.     

Measurement of high-pT single electrons from heavy-flavor decays in p + p collisions at square root of s = 200 GeV

The momentum distribution of electrons from decays of heavy flavor (charm and bottom) for midrapidity absolute value of y < 0.35 in p + p collisions at square root of s = 200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.3 < pT < 9 GeV/c. Two independent methods have been used to determine the heavy-flavor yields, and the results are in good agreement with each other. A fixed-order-plus-next-to-leading-log perturbative QCD calculation agrees with the data within the theoretical and experimental uncertainties, with the data/theory ratio of 1.71+/-0.02stat+/-0.18sys for 0.3 < pT < 9 GeV/c. The total charm production cross section at this energy has also been deduced to be sigma cc = 567+/-57stat+/-193sys microb.     

Neutral-kaon mixing from (2+1)-flavor domain-wall QCD

We present the first results for neutral-kaon mixing using (2+1)-flavors of domain-wall fermions. A new approach is used to extrapolate to the physical up and down quark masses from our numerical studies with pion masses in the range 240-420 MeV; only SU(2)_{L}xSU(2)_{R} chiral symmetry is assumed and the kaon is not assumed to be light. Our main result is B_{K};{MS[over ]}(2 GeV)=0.524(10)(28) where the first error is statistical and the second incorporates estimates for all systematic errors.