6,294 research outputs found
Antibound poles in cutoff Woods-Saxon and in Salamon-Vertse potentials
The motion of l=0 antibound poles of the S-matrix with varying potential
strength is calculated in a cutoff Woods-Saxon (WS) potential and in the
Salamon-Vertse (SV) potential, which goes to zero smoothly at a finite
distance. The pole position of the antibound states as well as of the
resonances depend on the cutoff radius, especially for higher node numbers. The
starting points (at potential zero) of the pole trajectories correlate well
with the range of the potential. The normalized antibound radial wave functions
on the imaginary k-axis below and above the coalescence point have been found
to be real and imaginary, respectively
Plasma tomographic reconstruction from tangentially viewing camera with background subtraction
Electron-impact ionization of atomic hydrogen at 2 eV above threshold
The convergent close-coupling method is applied to the calculation of fully
differential cross sections for ionization of atomic hydrogen by 15.6 eV
electrons. We find that even at this low energy the method is able to yield
predictive results with small uncertainty. As a consequence we suspect that the
experimental normalization at this energy is approximately a factor of two too
high.Comment: 10 page
A study of cross sections for excitation of pseudostates
Using the electron-hydrogen scattering Temkin-Poet model we investigate the
behavior of the cross sections for excitation of all of the states used in the
convergent close-coupling (CCC) formalism. In the triplet channel, it is found
that the cross section for exciting the positive-energy states is approximately
zero near-threshold and remains so until a further energy, equal to the energy
of the state, is added to the system. This is consistent with the step-function
hypothesis [Bray, Phys. Rev. Lett. {\bf 78} 4721 (1997)] and inconsistent with
the expectations of Bencze and Chandler [Phys. Rev. A {\bf 59} 3129 (1999)].
Furthermore, we compare the results of the CCC-calculated triplet and singlet
single differential cross sections with the recent benchmark results of
Baertschy et al. [Phys. Rev. A (to be published)], and find consistent
agreement.Comment: Four pages, 5 figure
First observation of Cherenkov rings with a large area CsI-TGEM-based RICH prototype
We have built a RICH detector prototype consisting of a liquid C6F14 radiator
and six triple Thick Gaseous Electron Multipliers (TGEMs), each of them having
an active area of 10x10 cm2. One triple TGEM has been placed behind the liquid
radiator in order to detect the beam particles, whereas the other five have
been positioned around the central one at a distance to collect the Cherenkov
photons. The upstream electrode of each of the TGEM stacks has been coated with
a 0.4 micron thick CsI layer.
In this paper, we will present the results from a series of laboratory tests
with this prototype carried out using UV light, 6 keV photons from 55Fe and
electrons from 90Sr as well as recent results of tests with a beam of charged
pions where for the first time Cherenkov Ring images have been successfully
recorded with TGEM photodetectors. The achieved results prove the feasibility
of building a large area Cherenkov detector consisting of a matrix of TGEMs.Comment: Presented at the International Conference NDIP-11, Lyon,July201
Screened alpha decay in dense astrophysical plasmas and magnetars
This paper shows that ultrastrong magnetic fields (such as those of
magnetars) and dense astrophysical plasmas can reduce the half life of alpha
decaying nuclei by many orders of magnitude. In such environments the
conventional Geiger-Nuttall law is modifed so that all half lives are shifted
to dramatically lower values. Those effects, which have never been investigated
before, may have significant implications on the universal abundances of heavy
radioactive elements and the cosmochronological methods that rely on them.Comment: 15 RevTex pages, 3 ps figures (minor revision). This work was
presented during the conference ''Supernova, 10 years of SN1993J'', April
2003, Valencia, Spain. Accepted for publication in Phys.Rev.
Systematical Approach to the Exact Solution of the Dirac Equation for A Special Form of the Woods-Saxon Potential
Exact solution of the Dirac equation for a special form of the Woods-Saxon
potential is obtained for the s-states. The energy eigenvalues and
two-component spinor wave functions are derived by using a systematical method
which is called as Nikiforov-Uvarov. It is seen that the energy eigenvalues
strongly depend on the potential parameters. In addition, it is also shown that
the non-relativistic limit can be reached easily and directly.Comment: 10 pages, no figures, submitted for Publicatio
Neutron radiation tolerance tests of optical and opto-electronic components for the CMS Muon Barrel Alignment
Results of gamma photon and neutron irradiations of Hamamatsu R5600-03/NG photomultiplier tubes
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