8 research outputs found
Confinement and short distance physics
We consider non-perturbative effects at short distances in theories with
confinement. The analysis is straightforward within the Abelian models in which
the confinement arises on classical level. In all cases considered (compact
U(1) in 3D and 4D, dual Abelian Higgs model) there are non-perturbative
contributions associated with short distances which are due to topological
defects. In QCD case, both classical and quantum effects determine the role of
the topological defects and the theoretical analysis has not been completed so
far. Generically, the topological defects would result in 1/Q^2 corrections
going beyond the standard Operator Product Expansion. We review existing data
on the power corrections and find that the data favor existence of the novel
corrections, at least at the mass scale of (1-2) GeV. We indicate crucial
experiments which could further clarify the situation on the phenomenological
side.Comment: 11 pp., Latex2e, 4 figures, epsfig.sty. Accepted for publication in
Physics Letters
Resonant electron spin-flip Raman scattering in CdTe and the diluted magnetic semiconductor Cd
Optimal alignment of mirror based pentaprisms for scanning deflectometric devices
In the recent work [Proc. of SPIE 7801, 7801-2/1-12 (2010), Opt. Eng. 50(5) (2011), in press], we have reported on improvement of the Developmental Long Trace Profiler (DLTP), a slope measuring profiler available at the Advanced Light Source Optical Metrology Laboratory, achieved by replacing the bulk pentaprism with a mirror based pentaprism (MBPP). An original experimental procedure for optimal mutual alignment of the MBPP mirrors has been suggested and verified with numerical ray tracing simulations. It has been experimentally shown that the optimally aligned MBPP allows the elimination of systematic errors introduced by inhomogeneity of the optical material and fabrication imperfections of the bulk pentaprism. In the present article, we provide the analytical derivation and verification of easily executed optimal alignment algorithms for two different designs of mirror based pentaprisms. We also provide an analytical description for the mechanism for reduction of the systematic errors introduced by a typical high quality bulk pentaprism. It is also shown that residual misalignments of an MBPP introduce entirely negligible systematic errors in surface slope measurements with scanning deflectometric devices
From x-ray telescopes to neutron scattering: Using axisymmetric mirrors to focus a neutron beam
We demonstrate neutron beam focusing by axisymmetric mirror systems based on a pair of mirrors
consisting of a confocal ellipsoid and hyperboloid. Such a system, known as a Wolter mirror
configuration, is commonly used in x-ray telescopes. The axisymmetric Wolter geometry allows
nesting of several mirror pairs to increase collection efficiency. We have implemented a system
containing four nested Ni mirror pairs, which was tested by focusing a polychromatic neutron beam at
the MIT Reactor. In addition, we have carried out extensive ray-tracing simulations of the mirrors and
their performance in different situations. The major advantages of the Wolter mirrors are nesting for
large angular collection, and aberration-free performance. We discuss how these advantages can be
utilized to benefit various neutron scattering methods, such as imaging, SANS, and time-of-flight
spectroscopy.United States. Dept. of Energy. Office of Basic Energy Sciences (award DE-FG02-09ER46556)United States. Dept. of Energy. Office of Basic Energy Sciences (award DE-FG02-09ER46557