The discretized flow on domains of attraction: a structural stability result

It is well known that, for stepsize sufficiently small, compactattractors of ordinary differential equations persist underdiscretization. The present paper describes the structure ofthe discrete-time dynamical system obtained via discretizationon A(M_h)\M_h where M_h is the approximate attractor and A(M_h)is its domain of attraction. The existence of a smooth embeddinginto a continuous-time parallelizable flow is proved. The constructioncan be used to define sections for discretizations and can beinterpreted as a justification of the method of modified equations.     

The mass of 29S

the mass of ²⁹S has been measured with the ³²S(τ, ⁶He) reaction at 70 MeV. The mass excess is ?3.16 ± 0.05 MeV.     

Photoproduction of straight phi(1020) mesons on the proton at large momentum transfer

The cross section for straight phi meson photoproduction on the proton has been measured for the first time up to a four-momentum transfer -t = 4 GeV2, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. At low four-momentum transfer, the differential cross section is well described by Pomeron exchange. At large four-momentum transfer, above -t = 1.8 GeV2, the data support a model where the Pomeron is resolved into its simplest component, two gluons, which may couple to any quark in the proton and in the straight phi.     

Cross sections and asymmetries for the reaction from threshold to 1 GeV

Total cross sections, differential cross sections and asymmetries for the reaction from threshold to 1 GeV have been measured. The outgoing π⁰ was detected by a 4π neutral meson spectrometer. Our data are compared with the corresponding np→NNπ^± reactions. The isoscalar partial cross sections are extracted from the relevant total cross sections. They are significant throughout the whole energy range. Below the Δ-region, energy-integrated differential cross sections show a large anisotropy difference between the neutral and charged pion channels, respectively. A partial-wave fit shows that the initial T = 0 state is dominated by the ³D₁ wave in this energy region. Finally, predictions of phenomenological models give reasonable good account of the measured observables but cannot reproduce the sign of the asymmetries.