3,749 research outputs found
Measurement of the energy spectrum of cosmic rays at the highest energies using data from Pierre Auger Observatory
We report a measurement of the flux of cosmic rays with unprecedented
precision and statistics using data from the Pierre Auger Observatory. Based on
fluorescence observations in coincidence with at least one station of the
surface detector we derive a spectrum for energies above 1 EeV. We also report
on the energy spectra obtained with the surface detector array. The spectral
features are presented in detail and the impact of systematic uncertainties on
these features are addressed.Comment: 6 pages, 8 figures, UHECR 2012 Symposium, CERN, Feb. 201
Facets of confinement and dynamical chiral symmetry breaking
The gap equation is a cornerstone in understanding dynamical chiral symmetry
breaking and may also provide clues to confinement. A symmetry-preserving
truncation of its kernel enables proofs of important results and the
development of an efficacious phenomenology. We describe a model of the kernel
that yields: a momentum-dependent dressed-quark propagator in fair agreement
with quenched lattice-QCD results; and chiral limit values: f_pi= 68 MeV and
= -(190 MeV)^3. It is compared with models inferred from studies of
the gauge sector.Comment: 5 pages, 3 figures; contribution to the proceedings of Quark Nuclear
Physics (QNP 2002), Juelich, Germany, 9-14 Jun 200
Differences between heavy and light quarks
The quark Dyson-Schwinger equation shows that there are distinct differences
between light and heavy quarks. The dynamical mass function of the light quarks
is characterised by a sharp increase below 1 GeV, whereas the mass function of
the heavy quarks is approximately constant in this infrared region. As a
consequence, the heavy-meson masses increase linearly with the current-quark
masses, whereas the light pseudoscalar meson masses are proportional to the
square root of the current-quark masses.Comment: 4 pages, 3 figures, Contribution to the IVth International Workshop
on Progress in Heavy Quark Physics, 20-22 Sept. 1997, Rostoc
Confinement Phenomenology in the Bethe-Salpeter Equation
We consider the solution of the Bethe-Salpeter equation in Euclidean metric
for a qbar-q vector meson in the circumstance where the dressed quark
propagators have time-like complex conjugate mass poles. This approximates
features encountered in recent QCD modeling via the Dyson-Schwinger equations;
the absence of real mass poles simulates quark confinement. The analytic
continuation in the total momentum necessary to reach the mass shell for a
meson sufficiently heavier than 1 GeV leads to the quark poles being within the
integration domain for two variables in the standard approach. Through Feynman
integral techniques, we show how the analytic continuation can be implemented
in a way suitable for a practical numerical solution. We show that the would-be
qbar-q width to the meson generated from one quark pole is exactly cancelled by
the effect of the conjugate partner pole; the meson mass remains real and there
is no spurious qbar-q production threshold. The ladder kernel we employ is
consistent with one-loop perturbative QCD and has a two-parameter infrared
structure found to be successful in recent studies of the light SU(3) meson
sector.Comment: Submitted for publication; 10.5x2-column pages, REVTEX 4, 3
postscript files making 3 fig
Dyson-Schwinger Equations - aspects of the pion
The contemporary use of Dyson-Schwinger equations in hadronic physics is
exemplified via applications to the calculation of pseudoscalar meson masses,
and inclusive deep inelastic scattering with a determination of the pion's
valence-quark distribution function.Comment: 4 pages. Contribution to the Proceedings of ``DPF 2000,'' the Meeting
of the Division of Particles and Fields of the American Physical Society,
August 9-12, 2000, Department of Physics, the Ohio State University,
Columbus, Ohi
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