36,228 research outputs found
Investigation of double beta decay with the NEMO-3 detector
The double beta decay experiment NEMO~3 has been taking data since February
2003. The aim of this experiment is to search for neutrinoless
() decay and investigate two neutrino double beta decay in
seven different isotopically enriched samples (Mo, Se,
Ca, Zr, Cd, Te and Nd). After analysis of
the data corresponding to 3.75 y, no evidence for decay in the
Mo and Se samples was found. The half-life limits at the 90%
C.L. are y and y, respectively.
Additionally for decay the following limits at the 90% C.L.
were obtained, y for Ca, y
for Zr and y for Nd. The
decay half-life values were precisely measured for all investigated isotopes.Comment: 12 pages, 4 figures, 5 tables; talk at conference on "Fundamental
Interactions Physics" (ITEP, Moscow, November 23-27, 2009
Regional and seasonal patterns of epipelagic fish assemblages from the central California Current
The coastal Pacific Ocean off northern and central California encompasses the strongest seasonal upwelling zone in the California Current ecosystem. Headlands and bays
here generate complex circulation features and confer unusual oceanographic complexity. We sampled the coastal epipelagic fish community of this region with a surface trawl in the summer and fall of 2000–05 to assess patterns of spatial and temporal community structure. Fifty-three species of fish were captured in 218 hauls at 34 fixed stations, with clupeiform species dominating. To examine spatial patterns, samples were grouped by location relative to a prominent headland at Point Reyes and the resulting
two regions, north coast and Gulf of the Farallones, were plotted by using nonmetric multidimensional scaling.
Seasonal and interannual patterns were also examined, and representative species were identified for each distinct community. Seven oceanographic variables measured concurrently with trawling were plotted by principal components analysis and tested for correlation with biotic
patterns. We found significant differences in community structure by region, year, and season, but no interaction among main effects. Significant differences in oceanographic
conditions mirrored the biotic patterns, and a match between biotic and hydrographic structure was detected.
Dissimilarity between assemblages was mostly the result of differences in abundance and frequency of occurrence of about twelve common species. Community patterns were best
described by a subset of hydrographic variables, including water depth, distance from shore, and any one of several correlated variables associated with upwelling intensity. Rather than discrete communities with clear borders and distinct member species, we found gradients in community
structure and identified stations with similar fish communities by region and by proximity to features such as
the San Francisco Bay
Perturbative and Nonperturbative Kolmogorov Turbulence in a Gluon Plasma
In numerical simulations of nonabelian plasma instabilities in the hard-loop
approximation, a turbulent spectrum has been observed that is characterized by
a phase-space density of particles with exponent , which is larger than expected from relativistic
scatterings. Using the approach of Zakharov, L'vov and Falkovich, we analyse
possible Kolmogorov coefficients for relativistic -particle
processes, which give at most perturbatively for an energy cascade.
We discuss nonperturbative scenarios which lead to larger values. As an extreme
limit we find the result generically in an inherently nonperturbative
effective field theory situation, which coincides with results obtained by
Berges et al.\ in large- scalar field theory. If we instead assume that
scaling behavior is determined by Schwinger-Dyson resummations such that the
different scaling of bare and dressed vertices matters, we find that
intermediate values are possible. We present one simple scenario which would
single out .Comment: published versio
Electron transfer through a multiterminal quantum ring: magnetic forces and elastic scattering effects
We study electron transport through a semiconductor quantum ring with one
input and two output terminals for an elastic scatterer present within one of
the arms of the ring. We demonstrate that the scatterer not only introduces
asymmetry in the transport probability to the two output leads but also reduces
the visibility of the Aharonov-Bohm conductance oscillations. This reduction
occurs in spite of the phase coherence of the elastic scattering and is due to
interruption of the electron circulation around the ring by the potential
defect. The results are in a qualitative agreement with a recent experiment by
Strambini et al. [Phys. Rev. B {\bf 79}, 195443 (2009)]. We also indicate that
the magnetic symmetry of the sum of conductance of both the output leads as
obtained in the experiment can be understood as resulting from the invariance
of backscattering to the input lead with respect to the magnetic field
orientation.Comment: submitted to PR
Lie Groups and mechanics: an introduction
The aim of this paper is to present aspects of the use of Lie groups in
mechanics. We start with the motion of the rigid body for which the main
concepts are extracted. In a second part, we extend the theory for an arbitrary
Lie group and in a third section we apply these methods for the diffeomorphism
group of the circle with two particular examples: the Burger equation and the
Camassa-Holm equation
Chemical Equilibration in Hadronic Collisions
We study chemical equilibration in out-of-equilibrium Quark-Gluon Plasma
using the first principles method of QCD effective kinetic theory, accurate at
weak coupling. In longitudinally expanding systems--relevant for relativistic
nuclear collisions--we find that for realistic couplings chemical equilibration
takes place after hydrodynamization, but well before local thermalization. We
estimate that hadronic collisions with final state multiplicities
live long enough to reach approximate
chemical equilibrium, which is consistent with the saturation of strangeness
enhancement observed in proton-proton, proton-nucleus and nucleus-nucleus
collisions.Comment: 7 pages, 3 figures, see also our companion paper arXiv:1811.03068, v2
small changes, published versio
Angular intricacies in hot gauge field theories
It is argued that in hot gauge field theories, "Hard Thermal Loops" leading
order calculations call for a definite sequence of angular averages and
discontinuity (or Imaginary part prescription) operations, and run otherwise
into incorrect results. The ten years old collinear singularity problem of hot
, provides a striking illustration of that fate.Comment: 14 pages, 1 figur
Recommended from our members
Larval fish in the vicinity of aquaculture intakes
Texas Parks and Wildlife Department has recently proposed that all facilities pumping water from Texas estuaries be fitted with 0.5 mm screening to prevent larval fish mortality at these facilities. Data on larval fish distributions in Texas estuaries is quite limited (Holt et al. 1990). This report presents the results of a pilot study to examine the impact on larval fishes and shrimps of pumping water into mariculture facilities at three sites on the central and southern Texas Coast. The primary objective of this study was to determine the species composition, density and size structure of ichthyoplankton populations in the vicinity of the intake structures of the three mariculture facilities during their spring and fall pumping seasons. A secondary objective was to determine what organisms were actually being pumped through the system.Final report for contract IAC(90-91)111.5Prepared for Texas A&M Sea Grant, Texas General Land OfficeFebruary 1991Marine Scienc
Looking for CP Violation in W Production and Decay
We describe CP violating observables in resonant and plus one
jet production at the Tevatron. We present simple examples of CP violating
effective operators, consistent with the symmetries of the Standard Model,
which would give rise to these observables. We find that CP violating effects
coming from new physics at the scale could in principle be observable at
the Tevatron with decays.Comment: 15 pgs with standard LATEX, 7 ps figures embedded with eps
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