155 research outputs found
Electron Scattering on 3He - a Playground to Test Nuclear Dynamics
The big spectrum of electron induced processes on 3He is illustrated by
several examples based on Faddeev calculations with modern nucleon-nucleon and
three-nucleon forces as well as exchange currents. The kinematical region is
restricted to a mostly nonrelativistic one where the three-nucleon c.m. energy
is below the pion production threshold and the three-momentum of the virtual
photon is sufficiently below the nucleon mass. Comparisons with available data
are shown and cases of agreement and disagreement are found. It is argued that
new and precise data are needed to systematically check the present day
dynamical ingredients.Comment: 27 pages, 24 figure
Accumulation of chromium metastable atoms into an Optical Trap
We report the fast accumulation of a large number of metastable 52Cr atoms in
a mixed trap, formed by the superposition of a strongly confining optical trap
and a quadrupolar magnetic trap. The steady state is reached after about 400
ms, providing a cloud of more than one million metastable atoms at a
temperature of about 100 microK, with a peak density of 10^{18} atoms.m^{-3}.
We have optimized the loading procedure, and measured the light shift of the
5D4 state by analyzing how the trapped atoms respond to a parametric
excitation. We compare this result to a theoretical evaluation based on the
available spectroscopic data for chromium atoms.Comment: 7 pages, 5 Figure
Anisotropic field dependence of the magnetic transition in Cu2Te2O5Br2
We present the results of measurements of the thermal conductivity of
Cu2Te2O5Br2, a compound where tetrahedra of Cu^{2+} ions carrying S=1/2 spins
form chains along the c-axis of the tetragonal crystal structure. The thermal
conductivity kappa was measured along both the c- and the a-direction as a
function of temperature between 3 and 300 K and in external magnetic fields H
up to 69 kOe, oriented both parallel and perpendicular to the c-axis. Distinct
features of kappa(T) were observed in the vicinity of T_N=11.4 K in zero
magnetic field. These features are unaltered in external fields which are
parallel to the c-axis, but are more pronounced when a field is applied
perpendicularly to the c-axis. The transition temperature increases upon
enhancing the external field, but only if the field is oriented along the
a-axis.Comment: 5 pages, 3 figure
Near-threshold production of omega mesons in the pn -> d omega reaction
The first measurement of the p n -> d omega total cross section has been
achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium
cluster-jet target. The momentum of the fast deuteron was measured in the ANKE
spectrometer at COSY-Juelich and that of the slow "spectator" proton p(sp) from
the p d -> p(sp) d omega reaction in a silicon telescope placed close to the
target. The cross sections lie above those measured for p p -> p p omega but
seem to be below theoretical predictions.Comment: 7 pages, 8 figures; second approach to describe the background has
been added; results changed insignificantly, EPJ in pres
Occupational exposure to nano-TiO2 in the life cycle steps of new depollutant mortars used in construction
The present work is focused on the measurement of workers exposure to nano-TiO2
in the life cycle steps of depollutant mortars. It has been done in the framework of the
SCAFFOLD project, which aims at the management of potential risks arising from the use of
manufactured nanomaterials in construction. Main findings can be summarized as follows: (1)
The occupational exposure to nano- TiO2 is below 0.3 mg/m3 for all measured scenarios. The
highest concentrations were measured during the cleaning task (in the nano- TiO2
manufacturing process) and during the application (spraying) of depollutant coatings on a wall.
(2) It was found a high release of particles above the background in several tasks as expected
due to the nature of the activities performed. The maximum concentration was measured
during drilling and during adding powder materials (mean total particle concentration up to
5.591E+04 particles/cm3 and 5.69E+04 particles/cm3). However, considering data on total
particle concentration released, no striking differences have been observed when tasks have
been performed using conventional materials in the sector (control) and when using materials
doped with nano-objects.European Commission's FP
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV
We report on the first measurement of the triangular , quadrangular
, and pentagonal charged particle flow in Pb-Pb collisions at 2.76
TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show
that the triangular flow can be described in terms of the initial spatial
anisotropy and its fluctuations, which provides strong constraints on its
origin. In the most central events, where the elliptic flow and
have similar magnitude, a double peaked structure in the two-particle azimuthal
correlations is observed, which is often interpreted as a Mach cone response to
fast partons. We show that this structure can be naturally explained from the
measured anisotropic flow Fourier coefficients.Comment: 10 pages, 4 figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/387
Planck Intermediate Results II: Comparison of Sunyaev–Zeldovich measurements from Planck and from the Arcminute Microkelvin Imager for 11 galaxy clusters
A comparison is presented of Sunyaev–Zeldovich measurements for 11 galaxy clusters as obtained by Planck and by the ground-based interferom- eter, the Arcminute Microkelvin Imager. Assuming a universal spherically-symmetric Generalised Navarro, Frenk & White (GNFW) model for the cluster gas pressure profile, we jointly constrain the integrated Compton-Y parameter (Y500) and the scale radius (θ500) of each cluster. Our resulting constraints in the Y500 − θ500 2D parameter space derived from the two instruments overlap significantly for eight of the clusters, although, overall, there is a tendency for AMI to find the Sunyaev–Zeldovich signal to be smaller in angular size and fainter than Planck. Significant discrepancies exist for the three remaining clusters in the sample, namely A1413, A1914, and the newly-discovered Planck cluster PLCKESZ G139.59+24.18. The robustness of the analysis of both the Planck and AMI data is demonstrated through the use of detailed simulations, which also discount confusion from residual point (radio) sources and from diffuse astrophysical foregrounds as possible explanations for the discrepancies found. For a subset of our cluster sample, we have investigated the dependence of our results on the assumed pressure profile by repeating the analysis adopting the best-fitting GNFW profile shape which best matches X-ray observations. Adopting the best-fitting profile shape from the X-ray data does not, in general, resolve the discrepancies found in this subset of five clusters. Though based on a small sample, our results suggest that the adopted GNFW model may not be sufficiently flexible to describe clusters universally
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