1,095 research outputs found
New light on electromagnetic corrections to the scattering parameters obtained from experiments on pionium
We calculate the electromagnetic corrections needed to obtain isospin
invariant hadronic pion-pion s-wave scattering lengths a^0, a^2 from the
elements a_cc, a_0c of the s-wave scattering matrix for the (\pi^+ \pi^-, \pi^0
\pi^0) system at the \pi^+ \pi^- threshold. These elements can be extracted
from experiments on pionium. Our calculation uses energy independent hadronic
pion-pion potentials that satisfactorily reproduce the low-energy phase shifts
given by two-loop chiral pertur- bation theory. We also take into account an
important relativistic effect whose inclusion influences the corrections
considerably.Comment: 14 pages including 3 figures. Uses elsart.cls. Some numbers have been
updated and a few typos have been correcte
The extraction of hadronic parameters from experiments on pionium
Experimental values of the lifetime of the 1s level of pionium and of the
difference between the energies of the 2s and 2p levels yield values of the
a(0c) and a(cc) elements of the s-wave scattering matrix for the 2-channel (pi+
pi-, pi0 pi0) system at the pi+ pi- threshold. We develop a method for
obtaining the isospin invariant quanties a20 - a00 and 2a00 + a20 from a(0c)
and a(cc). We emphasize that the isospin invariant scattering lengths a00 and
a20 universally used in the literature cannot be considered to be purely
hadronic quantities.Comment: 17 pages, Revtex, 1 postscript figure, new version of figure which
removes ghostscript problem
The effects of the new energy regime on economic capacity, production, and prices
Energy policy ; Production (Economic theory) ; Prices
Energy resources and potential GNP
Natural resources ; Gross national product
Electromagnetic corrections for the analysis of low energy pi-p scattering data
We calculate the electromagnetic corrections to the isospin invariant mixing
angle and to the two eigenphases for the s and p-waves for low energy pi-p
elastic and charge exchange scattering. These corrections have to be applied to
the nuclear quantities obtained from phase shift analyses of the experimental
data in order to obtain the hadronic phases. We compare our results with
earlier calculations and estimate the uncertainties in the corrections.Comment: 19 pages, 5 figures. Uses elsart.cls Accepted for publication in
Nuclear Physics
The effect of vacuum polarisation on muon-proton scattering at small energies and angles
We give a compact expression for the unpolarised differential cross section
for muon-proton scattering in the one photon exchange approximation. The effect
of adding the vacuum polarisation amplitude to the no-spin-flip amplitude for
one photon exchange is calculated at small energies and scattering angles and
is found to be negligible for present experiments.Comment: 6 pages, one figur
Hadronic Effects in the Pionium Ion
The hadronic properties of the pionium ion (Coulomb bound system of three
charged pions) are estimated using the results for the positronium ion
. It turns out that the hadronic shift of the ground state energy and
the lifetime of the pionium ion are approximately the same as for pionium.Comment: RevTex, 5 page
Birds of Lake McConaughy and the North Platte River Valley, Oshkosh to Keystone
Cedar Point Biological Station was established in 1975 at a site approximately one mile below Kingsley Dam in Keith County, Nebraska. Since that time, summer ornithology classes have been periodically offered beginning in 1977 when it was taught by Dr. Stephen Fretwell. A variety of ornithologists have kept records of the summer birds of the area. Beginning in 1970, when he first visited the area, the senior author has accumulated a large amount of data covering all seasons of the year, which form the primary basis for the seasonal information in this paper. In addition, much information was contributed by C. Fred Zeillemaker from late 1977 to early 1982, when he was Manager at nearby Crescent Lake National Wildlife Refuge. Other contributors include: Charles Brown, Craig Faanes, Don Mahoney, Dorothy and Mark Rasche, and Melly Zeillemaker.
Because of the unusual diversity of terrestrial and aquatic habitats within the rather circumscribed area of Lake McConaughy and adjoining localities, it is of special interest to ornithologists. Furthermore, the area is essentially in the middle of the east-west faunal transition zone in the Great Plains, so that a number of closely related species-pairs (buntings, grosbeaks, tanagers, orioles, et al.) are represented. Finally the annual concentration of biologists at Cedar Point makes it desirable that a comprehensive bird list for the area be prepared. The following is largely limited to the North Platte River Valley from Oshkosh east to the vicinity of Keystone as indicated in Figure 1. Major birding areas include the Oshkosh sewage lagoons, the Lewellen area, Ash Hollow State Historical Park, Clear Creek State Game Management Area, Lake McConaughy, Lake Ogallala, Keystone Lake, and Cedar Point Biological Station. Except where otherwise indicated, the observations are those of the authors
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