640 research outputs found
Orbiting valence quarks and their influence on the structure functions of the nucleon
It is shown that intrinsic orbital motion of the valence quarks has large
influences on the spin-dependent as well as the spin-averaged nucleon structure
functions. Its connection with the observed ``very small contribution of quark
spin to nucleon spin'' and the observed violation of Gottfried sum rule is
discussed.Comment: 10 pages (LaTeX) including 3 figure
Criticality in quark-gluon systems far beyond thermal and chemical equilibrium
Experimental evidence and theoretical arguments for the existence of
self-organized criticality in systems of gluons and quarks are presented. It is
observed that the existing data for high-transverse-momentum jet-production
exhibit striking regularities; and it is shown that, together with
first-principle considerations, such regularities can be used, not only to
probe the possible compositness of quarks, but also to obtain {\em direct
evidence} for, or against, the existence of critical temperature and/or
critical chemical potential in quark-gluon systems when hadrons are squeezed
together.Comment: 13 pages, including 1 figure and 1 tabl
Formation of color-singlet gluon-clusters and inelastic diffractive scattering
This is the extensive follow-up report of a recent Letter in which the
existence of self-organized criticality (SOC) in systems of interacting soft
gluons is proposed, and its consequences for inelastic diffractive scattering
processes are discussed. It is pointed out, that color-singlet gluon-clusters
can be formed in hadrons as a consequence of SOC in systems of interacting soft
gluons, and that the properties of such spatiotemporal complexities can be
probed experimentally by examing inelastic diffractive scattering. Theoretical
arguments and experimental evidences supporting the proposed picture are
presented --- together with the result of a systematic analysis of the existing
data for inelastic diffractive scattering processes performed at different
incident energies, and/or by using different beam-particles. It is shown in
particular that the size- and the lifetime-distributions of such gluon-clusters
can be directly extracted from the data, and the obtained results exhibit
universal power-law behaviors --- in accordance with the expected
SOC-fingerprints. As further consequences of SOC in systems of interacting soft
gluons, the -dependence and the -dependence of the double
differential cross-sections for inelastic diffractive scattering off
proton-target are discussed. Here stands for the four-momentum-transfer
squared, for the missing mass, and for the total c.m.s.
energy. It is shown, that the space-time properties of the color-singlet
gluon-clusters due to SOC, discussed above, lead to simple analytical formulae
for and for , and that the obtained
results are in good agreement with the existing data. Further experiments are
suggested.Comment: 67 pages, including 11 figure
The Influence of Mode-Mixity on Dynamic Failure Mode Transitions in Polycarbonate
The transition of a shear to opening type of failure mechanism has been reported for side impact experiments of notched or cracked plates (metallic alloys and Polycarbonate). The present paper addresses additional aspects of the phenomenon in relation to mode-mixity for actual fatigue cracks in Polycarbonate specimens. Two distinct experimental setups are used and systematically compared throughout the work: dominant mode II and dominant mode I loading. The experimental results show that the same characteristic failure mechanisms operate irrespective of the specimen geometry (loading mode) and crack-tip nature for a given impact velocity (evolution of the stress intensity factors).La transition des modes de rupture d'ouverture en cisaillement a été observée lors d'essais d'impact latéral de plaques entaillées ou fissurées (alliages métalliques et Polycarbonate). Cet article traite d'autres aspects de la transition en relation avec la mixité du chargement pour des fissures de fatigue dans du Polycarbonate. Nous utilisons et comparons systématiquement deux types d'expériences distinctes: chargement en mode 11 dominant ou en mode I dominant. Les résultats montrent que des mécanismes de ruine identiques opÚrent dans les deux cas, en fonction de la vitesse d'impact (evolution des facteurs d'intensité des contraintes) indépendemment de la géometrié de l'éprouvette ou de la stature de la fissure
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