4,886 research outputs found
Latest Results from the Heidelberg-Moscow Double Beta Decay Experiment
New results for the double beta decay of 76Ge are presented. They are
extracted from Data obtained with the HEIDELBERG-MOSCOW, which operates five
enriched 76Ge detectors in an extreme low-level environment in the GRAN SASSO.
The two neutrino accompanied double beta decay is evaluated for the first time
for all five detectors with a statistical significance of 47.7 kg y resulting
in a half life of (T_(1/2))^(2nu) = [1.55 +- 0.01 (stat) (+0.19) (-0.15)
(syst)] x 10^(21) years. The lower limit on the half-life of the 0nu beta-beta
decay obtained with pulse shape analysis is (T_(1/2))^(0_nu) > 1.9 x 10^(25)
[3.1 x 10^(25)] years with 90% C.L. (68% C.L.) (with 35.5 kg y). This results
in an upper limit of the effective Majorana neutrino mass of 0.35 eV (0.27 eV).
No evidence for a Majoron emitting decay mode or for the neutrinoless mode is
observed.Comment: 14 pages, revtex, 6 figures, Talk was presented at third
International Conference ' Dark Matter in Astro and Particle Physics' -
DARK2000, to be publ. in Proc. of DARK2000, Springer (2000). Please look into
our HEIDELBERG Non-Accelerator Particle Physics group home page:
http://www.mpi-hd.mpg.de/non_acc
Development of CGLARE: Design, Fabrication and Characterisation
Fibre Metal Laminates (FMLs) are hybrid materials consisting of metal layers bonded to fibre-reinforced polymer layers. CGLARE is an FML developed at NAL consisting of thin aluminum foil combined with carbon-epoxy and glass-epoxy prepreg materials. CGLARE is proposed as the candidate material for the leading edges of wing and empennage of an aircraft as it has superior characteristics in terms of shape retention (due to highly linearly elastic material like carbon/epoxy), energy absorption capability (due to layered structure and plastic deformation), lightning protection (due to the presence of aluminum layers), and also due to its cost effectiveness (lightweight construction and simple production techniques). This paper describes the issues regarding the development of CGLARE such as surface preparation of aluminum foils and bonding of aluminum with glass. Tensile, Compression, ILSS and Flexure testing of ASTM standard CGLARE specimens for different layups have been done. An important design issue is the internal residual stresses built into the laminate during curing due to differential coefficients of thermal expansion of the different material systems. The paper presents these results that indicate some properties of these material systems that could be exploited for energy absorption in the leading edges of the aircraft
Application of Non-Orthogonal Multiple Access in LTE and 5G Networks
As the latest member of the multiple access family, non-orthogonal multiple
access (NOMA) has been recently proposed for 3GPP Long Term Evolution (LTE) and
envisioned to be an essential component of 5th generation (5G) mobile networks.
The key feature of NOMA is to serve multiple users at the same
time/frequency/code, but with different power levels, which yields a
significant spectral efficiency gain over conventional orthogonal MA. This
article provides a systematic treatment of this newly emerging technology, from
its combination with multiple-input multiple-output (MIMO) technologies, to
cooperative NOMA, as well as the interplay between NOMA and cognitive radio.
This article also reviews the state of the art in the standardization
activities concerning the implementation of NOMA in LTE and 5G networks.Comment: to appear in IEEE Communications Magazin
The Radius of Metric Subregularity
There is a basic paradigm, called here the radius of well-posedness, which
quantifies the "distance" from a given well-posed problem to the set of
ill-posed problems of the same kind. In variational analysis, well-posedness is
often understood as a regularity property, which is usually employed to measure
the effect of perturbations and approximations of a problem on its solutions.
In this paper we focus on evaluating the radius of the property of metric
subregularity which, in contrast to its siblings, metric regularity, strong
regularity and strong subregularity, exhibits a more complicated behavior under
various perturbations. We consider three kinds of perturbations: by Lipschitz
continuous functions, by semismooth functions, and by smooth functions,
obtaining different expressions/bounds for the radius of subregularity, which
involve generalized derivatives of set-valued mappings. We also obtain
different expressions when using either Frobenius or Euclidean norm to measure
the radius. As an application, we evaluate the radius of subregularity of a
general constraint system. Examples illustrate the theoretical findings.Comment: 20 page
Thermodynamic analysis of the Quantum Critical behavior of Ce-lattice compounds
A systematic analysis of low temperature magnetic phase diagrams of Ce
compounds is performed in order to recognize the thermodynamic conditions to be
fulfilled by those systems to reach a quantum critical regime and,
alternatively, to identify other kinds of low temperature behaviors. Based on
specific heat () and entropy () results, three different types of
phase diagrams are recognized: i) with the entropy involved into the ordered
phase () decreasing proportionally to the ordering temperature
(), ii) those showing a transference of degrees of freedom from the
ordered phase to a non-magnetic component, with their jump
() vanishing at finite temperature, and iii) those ending in a
critical point at finite temperature because their do not decrease
with producing an entropy accumulation at low temperature.
Only those systems belonging to the first case, i.e. with as
, can be regarded as candidates for quantum critical behavior.
Their magnetic phase boundaries deviate from the classical negative curvature
below \,K, denouncing frequent misleading extrapolations down to
T=0. Different characteristic concentrations are recognized and analyzed for
Ce-ligand alloyed systems. Particularly, a pre-critical region is identified,
where the nature of the magnetic transition undergoes significant
modifications, with its discontinuity strongly
affected by magnetic field and showing an increasing remnant entropy at . Physical constraints arising from the third law at are discussed
and recognized from experimental results
Globalization, the ambivalence of European integration and the possibilities for a post-disciplinary EU studies
Using the work of Manuel Castells as a starting point, this article explores the ambivalent relationship between globalization and European integration and the variety of ways in which the mainstream political science of the EU has attempted to deal with this issue. The analysis here suggests that various 'mainstreaming' disciplinary norms induce types of work that fail to address fully the somewhat paradoxical and counter-intuitive range of possible relationships between globalization and European integration. The article explores critically four possible analytical ways out of this paradox—abandonment of the concept of globalization, the development of definition precision in globalization studies, the reorientation of work to focus on globalization as discourse, and inter- and post-disciplinarity. The argument suggests that orthodox discussions of the relationship require a notion of social geography that sits at odds with much of the literature on globalization and while greater dialogue between disciplines is to be welcomed, a series of profound epistemological questions need to be confronted if studies of the interplay between global and social process are to be liberated from their disciplinary chains
On the Quantitative Impact of the Schechter-Valle Theorem
We evaluate the Schechter-Valle (Black Box) theorem quantitatively by
considering the most general Lorentz invariant Lagrangian consisting of
point-like operators for neutrinoless double beta decay. It is well known that
the Black Box operators induce Majorana neutrino masses at four-loop level.
This warrants the statement that an observation of neutrinoless double beta
decay guarantees the Majorana nature of neutrinos. We calculate these
radiatively generated masses and find that they are many orders of magnitude
smaller than the observed neutrino masses and splittings. Thus, some lepton
number violating New Physics (which may at tree-level not be related to
neutrino masses) may induce Black Box operators which can explain an observed
rate of neutrinoless double beta decay. Although these operators guarantee
finite Majorana neutrino masses, the smallness of the Black Box contributions
implies that other neutrino mass terms (Dirac or Majorana) must exist. If
neutrino masses have a significant Majorana contribution then this will become
the dominant part of the Black Box operator. However, neutrinos might also be
predominantly Dirac particles, while other lepton number violating New Physics
dominates neutrinoless double beta decay. Translating an observed rate of
neutrinoless double beta decay into neutrino masses would then be completely
misleading. Although the principal statement of the Schechter-Valle theorem
remains valid, we conclude that the Black Box diagram itself generates
radiatively only mass terms which are many orders of magnitude too small to
explain neutrino masses. Therefore, other operators must give the leading
contributions to neutrino masses, which could be of Dirac or Majorana nature.Comment: 18 pages, 4 figures; v2: minor corrections, reference added, matches
journal version; v3: typo corrected, physics result and conclusions unchange
A Large Scale Double Beta and Dark Matter Experiment: GENIUS
The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated
the large potential of double beta decay to search for new physics beyond the
Standard Model. To increase by a major step the present sensitivity for double
beta decay and dark matter search much bigger source strengths and much lower
backgrounds are needed than used in experiments under operation at present or
under construction. We present here a study of a project proposed recently,
which would operate one ton of 'naked' enriched GErmanium-detectors in liquid
NItrogen as shielding in an Underground Setup (GENIUS). It improves the
sensitivity to neutrino masses to 0.01 eV. A ten ton version would probe
neutrino masses even down to 10^-3 eV. The first version would allow to test
the atmospheric neutrino problem, the second at least part of the solar
neutrino problem. Both versions would allow in addition significant
contributions to testing several classes of GUT models. These are especially
tests of R-parity breaking supersymmetry models, leptoquark masses and
mechanism and right-handed W-boson masses comparable to LHC. The second issue
of the experiment is the search for dark matter in the universe. The entire
MSSM parameter space for prediction of neutralinos as dark matter particles
could be covered already in a first step of the full experiment - with the same
purity requirements but using only 100 kg of 76Ge or even of natural Ge -
making the experiment competitive to LHC in the search for supersymmetry.
The layout of the proposed experiment is discussed and the shielding and
purity requirements are studied using GEANT Monte Carlo simulations. As a
demonstration of the feasibility of the experiment first results of operating a
'naked' Ge detector in liquid nitrogen are presented.Comment: 22 pages, 12 figures, see also
http://pluto.mpi-hd.mpg.de/~betalit/genius.htm
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