30,456 research outputs found
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
A dynamical metric and its ground state from the breaking down of the topological invariance of the Euler characteristic
Quantum state wave functionals are constructed in exact form for the
graviton-like field theory obtained by breaking down the topological symmetry
of the string action related with the Euler characteristic of the
world-surface; their continuous and discrete symmetries are discussed. The
comparison with the so-called Chern-Simons state, which may be inappropriate as
quantum state, allows us to conclude that the found wave functionals will give
a plausible approximation to the ground state for the considered field theory
Sea quark and gluon polarization in the nucleon at NLO accuracy
We investigate the sea quark polarization in the nucleon by means of a
combined next to leading order analysis to the recently enlarged set of
inclusive and semi-inclusive polarized deep inelastic scattering data. Using
the Lagrange multiplier method, we asses the uncertainty inherent to the
extraction of the different spin dependent parton densities in a QCD global
fit, and the impact of the increased set of semi-inclusive data now available.
We comment on future prospects at RHIC and JLAB and their potential impact in
the future determination of polarized parton densities.Comment: 15 pages, 9 figures, 3 table
Extraction of polarized parton densities from polarized DIS and SIDIS
We present results on the quark and gluon polarization in the nucleon
obtained in a combined next to leading order analysis to the available
inclusive and semi-inclusive polarized deep inelastic scattering data.Comment: Talk given at XIII International Workshop on Deep Inelastic
Scattering, April,27 - May,1, 2005, Madison, Wisconsin, USA, 4 pages, 2
figure
The spectra of mixed He-He droplets
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of He atoms bound to a cluster of He atoms, by
using a previously determined optimum filling of single-fermion orbits with
well defined orbital angular momentum , spin and parity quantum numbers.
The study concentrates on the energies and shapes of the three kinds of states
for which the fermionic part of the wave function is a single Slater
determinant: maximum or maximum states within a given orbit, and fully
polarized clusters. The picture that emerges is that of systems with strong
shell effects whose binding and excitation energies are essentially determined
over configuration at fixed number of particles and spin, i.e., by the monopole
properties of an effective Hamiltonian.Comment: 14 pages, 15 figure
Theoretical Constraints on the Vacuum Oscillation Solution to the Solar Neutrino Problem
The vacuum oscillation (VO) solution to the solar anomaly requires an
extremely small neutrino mass splitting, Delta m^2_{sol}\leq 10^{-10} eV^2. We
study under which circumstances this small splitting (whatever its origin) is
or is not spoiled by radiative corrections. The results depend dramatically on
the type of neutrino spectrum. If m_1^2 \sim m_2^2 \geq m_3^2, radiative
corrections always induce too large mass splittings. Moreover, if m_1 and m_2
have equal signs, the solar mixing angle is driven by the renormalization group
evolution to very small values, incompatible with the VO scenario (however, the
results could be consistent with the small-angle MSW scenario). If m_1 and m_2
have opposite signs, the results are analogous, except for some small (though
interesting) windows in which the VO solution may be natural with moderate
fine-tuning. Finally, for a hierarchical spectrum of neutrinos, m_1^2 << m_2^2
<< m_3^2, radiative corrections are not dangerous, and therefore this scenario
is the only plausible one for the VO solution.Comment: 13 pages, LaTeX, 3 ps figures (psfig.sty
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