Efficient multi-keV X-ray sources from Ti-doped aerogel targets

We have measured the production of hnu approximately 4.7 keV x rays from low-density Ti-doped aerogel (rho approximately 3 mg/cc) targets at the OMEGA laser facility (University of Rochester), with the goal of maximizing x-ray output. Forty OMEGA beams (lambda(L)=0.351 microm) illuminated the two cylindrical faces of the target with a total power that ranged from 7 to 14 TW. The laser fully ionizes the target (n(e)/n(crit)相似文献   

Double helicity asymmetry in inclusive midrapidity pi0 production for polarized p+p collisions at square root s = 200 GeV

We present a measurement of the double longitudinal spin asymmetry in inclusive pi(0) production in polarized proton-proton collisions at sqrt[s]=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 0.27. The measurements are the first in a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta 1-5 GeV/c at midrapidity, where next-to-leading-order perturbative quantum chromodynamic (NLO pQCD) calculations well describe the unpolarized cross section. The observed asymmetry is small and is compared to a NLO pQCD calculation with a range of polarized gluon distributions.     

Nuclear modification factors for hadrons at forward and backward rapidities in deuteron-gold collisions at sqrt[s(NN)]=200 GeV

We report on charged hadron production in deuteron-gold reactions at sqrt[s(NN)]=200 GeV. Our measurements in the deuteron direction cover 1.4相似文献   

Phase transitions and local minima of the action

We present evidence that non-trivial, non-degenerate local minima of the one-plaquette action in 4-dimensional lattice gauge theories with continuous gauge groups, give rise to a line of first-order “discreteness” phase transitions, persisting down to the region where the non-trivial minima become unstable. We illustrate this mechanism by analysing an extended model, involving the traces in the fundamental and six representation of SU(3), in which neither the topology, nor the group theoretic properties of the centre seem to play any role.     

A simple one-dimensional model for the three-dimensional vorticity equation

A simple qualitative one-dimensional model for the 3-D vorticity equation of incompressible fluid flow is developed. This simple model is solved exactly; despite its simplicity, this equation retains several of the most important structural features in the vorticity equations and its solutions exhibit some of the phenomena observed in numerical computations for breakdown for the 3-D Euler equations.     

The use of the CNDO method in spectroscopy: VII. Changes in dipole moment upon excitation

The results of the calculations of changes in dipole moment upon excitation of some organic molecules are discussed in connection with recent high resolution spectroscopic measurements of the same quantities. Calculations are reported for several substituted benzenes, several azines, and for formaldehyde, propynal, formyl fluoride, difluorodiazirine and azulene. The calculations were carried out within the CNDO/S parametrization scheme.     

Leading-particle suppression and surface emission in nucleus-nucleus collisions

After a short summary of the predictions of the Parton Quenching Model (PQM) for the nuclear modification factor and its centrality dependence in Au?Au collisions at RHIC, we concentrate on back-to-back jet-like correlations at high transverse momentum. We illustrate how this probe is biased by the surface effect.     

Absence of Proper Nondegenerate Generalized Self-Similar Singularities

We present a general covariance property and use it to prove that proper nondegenerate self-similar blow-up is not possible for active scalar equations.