6,911 research outputs found
What went wrong with: "The Interaction of Neutrons With 7Be: "Lack of Standard Nuclear Physics Solution to the "Primordial 7Li Problem"", by M. Gai [arXiv:1812.09914v1]?
We comment here on results of the project aimed at measuring the 7Be(n,x)
reactions at SARAF, Israel, in 2016, posted by M. Gai in [arXiv:1812.09914v1]
without the knowledge of parts of the collaboration and against the explicit
veto of the collaborators and the administration of the Paul Scherrer Institut,
Switzerland. We address both the experimental shortcomings and the drawbacks in
project conduction. M. Gais preprint is labeled as "on behalf of the SARAF
Israel-US-Switzerland Collaboration", the author list is given as a reference
to another unpublished contribution (cited as [27]) to the NPA8 conference in
June 2017 in Catania). However, M. Gai did never have the right to report on
unpublished proprietary data of the entire collaboration, and he was not
authorized to act "on behalf of the collaboration". The contribution is
declared as "accepted for publication", but in fact was retracted during the
refereeing process. After several careful data evaluations, we have to state
that the results of these measurements are not trustworthy and neither the
given experimental data basis nor the corresponding data analysis can be
improved further. Therefore, we requested to retract the posting immediately
[arXiv:1904.03023]. We have to emphasize that, in our opinion, arXiv is not the
appropriate platform for handling frictions in a collaboration. These problems
should have been solved internally before publishing. Unfortunately, with his
single-handed posting against the explicit disagreement of parts of the
collaboration, M. Gai did not leave another possibility. With the present
article, we expressed all our concerns and objections and we consider herewith
the public discussion of this issue as closed.Comment: arXiv admin note: This version has been removed by arXiv
administrators due to copyright infringemen
Calculation of the Regularized Vacuum Energy in Cavity Field Theories
A novel technique based on Schwinger's proper time method is applied to the
Casimir problem of the M.I.T. bag model. Calculations of the regularized vacuum
energies of massless scalar and Dirac spinor fields confined to a static and
spherical cavity are presented in a consistent manner. While our results agree
partly with previous calculations based on asymptotic methods, the main
advantage of our technique is that the numerical errors are under control.
Interpreting the bag constant as a vacuum expectation value, we investigate
potential cancellations of boundary divergences between the canonical energy
and its bag constant counterpart in the fermionic case. It is found that such
cancellations do not occur.Comment: 14 pages, 4 figures, accepted for publication in Eur.Phys.J.
Vacuum structure of a modified MIT Bag
An alternative to introducing and subsequently renormalizing classical
parameters in the expression for the vacuum energy of the MIT bag for quarks is
proposed in the massless case by appealing to the QCD trace anomaly and scale
separation due to asymptotic freedom. The explicit inclusion of gluons implies
an unrealistically low separation scale.Comment: 5 pages, 2 figure
Effect of area ratio on the performance of a 5.5:1 pressure ratio centrifugal impeller
A centrifugal impeller which was initially designed for a pressure ratio of approximately 5.5 and a mass flow rate of 0.959 kg/sec was tested with a vaneless diffuser for a range of design point impeller area ratios from 2.322 to 2.945. The impeller area ratio was changed by successively cutting back the impeller exit axial width from an initial value of 7.57 mm to a final value of 5.97 mm. In all, four separate area ratios were tested. For each area ratio a series of impeller exit axial clearances was also tested. Test results are based on impeller exit surveys of total pressure, total temperature, and flow angle at a radius 1.115 times the impeller exit radius. Results of the tests at design speed, peak efficiency, and an exit tip clearance of 8 percent of exit blade height show that the impeller equivalent pressure recovery coefficient peaked at a design point area ratio of approximately 2.748 while the impeller aerodynamic efficiency peaked at a lower value of area ratio of approximately 2.55. The variation of impeller efficiency with clearance showed expected trends with a loss of approximately 0.4 points in impeller efficiency for each percent increase in exit axial tip clearance for all impellers tested
New Records of Leptothorax Wilsoni From Western North America
The parasitic ant Leptothorax wilsoni Heinze, 1989 was recorded
from New Hampshire, Quebec, and New Brunswick. We report on
colonies found in two sites in Jasper National Park, Alberta and in
one site south of Glacier National Park, Montana. The host species
in the west is apparently the same as in the eastern area. Brachypterous
intermorphic and fully alate gynomorphic females were
found together in two colonies, confirming that L. wilsoni is a
species with queen polymorphism. L. wilsoni workers and host
species queens lacked in all colonies, as in the samples from eastern
North America
Bounds on Lorentz and CPT Violation from the Earth-Ionosphere Cavity
Electromagnetic resonant cavities form the basis of many tests of Lorentz
invariance involving photons. The effects of some forms of Lorentz violation
scale with cavity size. We investigate possible signals of violations in the
naturally occurring resonances formed in the Earth-ionosphere cavity.
Comparison with observed resonances places the first terrestrial constraints on
coefficients associated with dimension-three Lorentz-violating operators at the
level of 10^{-20} GeV.Comment: 8 pages REVTe
Hadron masses in cavity quantum chromodynamics to order
The non-divergent diagrams describing two-gluon exchange and annihilation
between quarks and antiquarks are calculated in the Feynman gauge, based on
quantum chromodynamics in a spherical cavity. Using the experimental ,
, , and masses to fit the free parameters of the M.I.T.\
bag model, the predicted states agree very well with the observed low-lying
hadrons. As expected, the two-gluon annihilation graphs lift the degeneracy of
the and , while the and remain degenerate.
Diagonalizing the subspace Hamiltonian yields a very good value
for the mass of the meson.Comment: 15 pages, 2 figure
Possibilities of preparation of exotic radionuclide samples at PSI for scientific investigations
The interactions of high-energy protons with matter produce a large variety of radionuclides due to the diversity of the induced nuclear reactions. Some of those isotopes are very rare, exotic, and, in many cases, difficult to produce by complementary methods. Valuable isotopes, interesting for scientific and technological applications, can be extracted from samples stemming from the surroundings or components of a proton accelerator, in particular if the load of the initial particle current is relatively high (esp. in the Megawatt range). Since PSI operates one of the most powerful high-energy proton accelerators world-wide, this facility is best-suited for an R&D program aimed at "harvesting” such isotopes. An initiative called ERAWAST (Exotic Radionuclides from Accelerator Waste for Science and Technology) was started in 2006 in order to identify and motivate potential users. After six years, first achievements as well as realistic future plans for front-end experiments are available. The present contribution describes radiochemical separation techniques for selected examples, summarizes the most prominent results and gives an outlook on the upcoming experiments within the scope of the ERAWAST progra
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