QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

Multinozzle gas-dynamic molecular-beam source

The results of an experimental investigation of a multinozzle gas-dynamic molecular-beam source, in which the working material is introduced directly into a supersonic jet of a buffer gas, are presented. The source is designed to create slow cold beams of atoms and molecules. Time-of-flight profiles of the beams of the N2 buffer gas and the working material SF6 formed by a source with six nozzles are presented. The measured parameters of the flow field of the buffer gas are compared with the results of calculations for an axisymmetric nozzle with an inner body having an annular critical cross section. The results obtained show that multinozzle designs can be used, in principle, in molecular-beam sources instead of axisymmetric nozzles with an inner body. This permits relaxation of the requirements placed on the accuracy needed in fabricating such sources, reduction of the buffer gas flow rate, and the employment of fairly simple schemes for recycling the buffer gas. © 1997 American Institute of Physics

Application of the particle-in-cell method to calculate the parameters of molecular beams from gasdynamic sources

The particle-in-cell method is used to calculate the flow fields of gases formed by supersonic nozzles of different shapes under flow conditions typical of gasdynamic sources of molecular beams. The proposed calculation scheme is tested by comparing the calculated flow fields from an acoustic nozzle with the semiempirical calculations made by Ashkenas and Sherman. For a nozzle with a conical supersonic section the calculations are compared with the results of time-of-flight measurements made using the molecular beam generator at the St. Petersburg Institute of Nuclear Physics of the Russian Academy of Sciences. Prospects for the further use of these calculation methods to develop and optimize gasdynamic sources of molecular beams are discussed. © 1998 American Institute of Physics