35,987 research outputs found
A new approach to the solar oxygen abundance problem
In this work we present new data that sets strong constraints on the solar
oxygen abundance. Our approach, based on the analysis of spectro-polarimetric
observations, is almost model-independent and therefore extremely robust. The
asymmetry of the Stokes V profile of the 6300 A [OI] and NiI blend is used as
an indicator of the relative abundances of these two elements. The peculiar
shape of the profile requires a value of EO = 730+/-100 ppm (parts per
million), or logEO = 8.86+/-0.07 in the logarithmic scale commonly used in
Astrophysics. The uncertainty range includes the model dependence as well as
uncertainties in the oscillator strengths of the lines. We emphasize that the
very low degree of model dependence in our analysis makes it very reliable
compared to traditional determinations.Comment: Accepted for publication in The Astrophysical Journal Letters. 12
pages, 3 figures, referee format. This is the replacement of a previous
version of the paper. Our revised analysis takes into consideration the
formation of molecules, resulting in a substantially larger value for the
derived Oxygen abundanc
Minimal mass-size of a stable 3He cluster
The minimal number of 3He atoms required to form a bound cluster has been
estimated by means of a Diffusion Monte Carlo procedure within the fixed-node
approximation. Several importance sampling wave functions have been employed in
order to consider different shell-model configurations. The resulting upper
bound for the minimal number is 32 atoms.Comment: 2 pages, no figure
Consistency in NLO analyses of inclusive and semi-inclusive polarized DIS data
We perform a detailed study of the consistency between different sets of
polarized deep inelastic scattering data and theory, from the standpoint of a
next to leading order QCD global analysis, and following the criteria proposed
by Collins and Pumplin. In face of recent suggestions that challenge the usual
assumption about parent parton spin independence of unpolarized fragmentation
functions, we specially focus on polarized semi-inclusive data.Comment: 17 pages, 5 figure
Constraints on gluon polarization in the nucleon at NLO accuracy
We compare constraints on the gluon polarization in the nucleon obtained in
next to leading order global QCD fits to polarized deep inelastic scattering
data with those coming from observables more directly linked to the gluon
polarization, such as the double spin asymmetry measured by Phenix at RHIC, and
high-pT hadron production studied by COMPASSComment: 4 pages, 3 figures, 1 tabl
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